Editorial

4 pages, 662 KiB

Open AccessEditorial

Strategies for Tree Improvement under Stress Conditions

by Jie Luo and Wentao Hu

Forests 2023, 14(7), 1320; https://doi.org/10.3390/f14071320 - 27 Jun 2023

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Forests are vital ecosystems, covering a significant portion of the Earth’s land area and providing essential ecological services and valuable products for human society [...] Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

Research

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15 pages, 2633 KiB

Open AccessArticle

Hibiscus hamabo Rootstock-Grafting Improves Photosynthetic Capacity of Hibiscus syriacus under Salt Stress

by Shuqing Zhang, Wanwen Yu, Zhiguo Lu, Peng Xiang, Zhiquan Wang, Jianfeng Hua, Chunsun Gu, Jinfeng Cai and Yan Lu

Forests 2023, 14(6), 1226; https://doi.org/10.3390/f14061226 - 13 Jun 2023

Cited by 1 | Viewed by 1525

Abstract

Hibiscus syriacus, a woody ornamental plant with great economic value, is vulnerable to salinity. Hence, its cultivation in saline areas is severely restricted. Although grafting H. syriacus onto H. hamabo rootstock can greatly improve H. syriacus’s salt resistance, the photosynthetic response [...] Read more.

Hibiscus syriacus, a woody ornamental plant with great economic value, is vulnerable to salinity. Hence, its cultivation in saline areas is severely restricted. Although grafting H. syriacus onto H. hamabo rootstock can greatly improve H. syriacus’s salt resistance, the photosynthetic response of H. syriacus to grafting and salt stress remains largely unknown. To address this question, self-rooted (Hs), self-grafted (Hs/Hs), and H. hamabo-grafted (Hs/Hh) H. syriacus were exposed to 0 or 300 mM NaCl. Salt significantly reduced the net and maximum photosynthetic rates, chlorophyll content, and maximum (Fv/Fm) and actual (ΦPSII) photochemical quantum yield of photosystem II (PSII), as well as the apparent electron transport rate, in Hs and Hs/Hs. However, these reductions were largely alleviated when H. syriacus was grafted onto H. hamabo. In line with the changes in the chlorophyll fluorescence parameters, the expression of genes encoding subunits of PSII and PSI in Hs/Hh was higher than that in Hs and Hs/Hs under saline conditions. Moreover, H. hamabo rootstock grafting upregulated the genes involved in the Calvin–Benson–Bassham cycle in H. syriacus under salt conditions. These results indicate that grafting can ameliorate the inhibition of salinity on the photosynthetic capacity of H. syriacus, mainly resulting from alleviated limitations on photosynthetic pigments, photochemical efficiency, and the Calvin–Benson–Bassham cycle. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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12 pages, 3083 KiB

Open AccessArticle

The Synergistic Effects of AMF Inoculation and Boron Deficiency on the Growth and Physiology of Camellia oleifera Seedlings

by Junying Liu, Mengxue Zhang, Jie Fan, Wenna Ding, Longsheng Chen, Jie Luo, Yongzhong Liu and Li Mei

Forests 2023, 14(6), 1126; https://doi.org/10.3390/f14061126 - 30 May 2023

Cited by 3 | Viewed by 1126

Abstract

Arbuscular mycorrhizal fungi (AMF) symbiosis has been shown to improve the ability to obtain nutrients and resist adverse environmental conditions. However, there are few studies on the functions of AMF in the absorption and accumulation of boron (B). Moreover, it is still unclear [...] Read more.

Arbuscular mycorrhizal fungi (AMF) symbiosis has been shown to improve the ability to obtain nutrients and resist adverse environmental conditions. However, there are few studies on the functions of AMF in the absorption and accumulation of boron (B). Moreover, it is still unclear whether the root colonization rates of AMF are limited by B deficiency. In this study, Camellia oleifera seedlings were planted in normal and boron-deficient substrates, and the seedlings were inoculated with Funneliformis mosseae or left uninoculated. The growth and physiological indices of C. oleifera seedlings were determined. The results of this experiment indicate that AMF inoculation increased the plant biomass, B content, B accumulation, and antioxidant enzyme activity in both normal and boron-deficient C. oleifera seedlings. Furthermore, boron deficiency resulted in a decrease in the AMF root colonization efficiency and the inhibition of C. oleifera seedlings’ growth and physiological activity. These findings suggest that AMF inoculation could improve the resistance to B-deficiency stress. Additionally, the colonization efficiency of AMF was adversely affected by B deficiency; thus, AMF play a cooperative role with B in the growth and physiological functions of plants. The results provide a theoretical basis for taking measures to solve B-deficiency stress in C. oleifera and other plants’ cultivation. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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17 pages, 2573 KiB

Open AccessArticle

More Effective Protection Supports Male Better Than Female Siblings over Water Deficit in Artificially Bred Poplar Hybrids

by Fugui Chen, Yu Gong, Shuangyan Liu, Yiyun Wang, Linjie Luo, Guoping Zhu and Han Zhao

Forests 2023, 14(5), 995; https://doi.org/10.3390/f14050995 - 11 May 2023

Cited by 1 | Viewed by 1188

Abstract

Sexually dimorphic response to stress has been observed in assorted natural dioecious plants. Up to now, few studies have focused on the difference of stress responses between artificially bred siblings. To determine the sexual dimorphism between artificially bred sibling poplar trees, we conducted [...] Read more.

Sexually dimorphic response to stress has been observed in assorted natural dioecious plants. Up to now, few studies have focused on the difference of stress responses between artificially bred siblings. To determine the sexual dimorphism between artificially bred sibling poplar trees, we conducted a study comparing the response to water deficit between male and female Populus × euramericana siblings. This pair of hybrids was analyzed in terms of growth, photosynthesis, membrane injury and repair systems, as well as gene regulation patterns. The female and male siblings presented distinct responses to water deficit, with greater inhibition in females’ growth and photosynthesis. The results also displayed that in females, relative electrolyte leakage and malonaldehyde content were higher than those in males under water deficit conditions. On the other hand, water deficit caused a greater increase in both SOD activity and POD activity in males than those in females. Consistent with these physiological differences, the expression of several stress-related genes, including SOD, GST, bHLH35, and PsbX1, was regulated differently between female and male hybrids by water deficit stress. Higher expression of SOD in moderate-water-deficit-treated females and higher GST, bHLH35 expression in both moderate- and severe-water-deficit-treated females suggest that the female sib is more sensitive, whilst higher expression of SOD in severe-water-deficit-treated males and higher PsbX1 expression in water-deficit-treated males testify that males protect cells better. To achieve an integrated view, all these variables were analyzed through the use of a principal component analysis and a total discrepancy between the sexes in their response to water deficit was demonstrated. The results indicate that, compared with male poplar sibs, females are more sensitive, but deploy a weaker protective apparatus to deal with water deficit. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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16 pages, 3600 KiB

Open AccessArticle

Comparative RNA-Seq Analysis Reveals the Organ-Specific Transcriptomic Response to Zinc Stress in Mulberry

by Shuai Huang, Xiaoru Kang, Ting Yu, Keermula Yidilisi, Lin Zhang, Xu Cao, Nan Chao and Li Liu

Forests 2023, 14(4), 842; https://doi.org/10.3390/f14040842 - 20 Apr 2023

Cited by 1 | Viewed by 1402

Abstract

Mulberry (Morus, Moraceae) is an important economic plant that is considered zinc-rich. Zinc (Zn) is a micronutrient that plays vital roles in various bio-processes in plants and animals. In the present study, a comparative transcriptome analysis associated with physiological indicators [...] Read more.

Mulberry (Morus, Moraceae) is an important economic plant that is considered zinc-rich. Zinc (Zn) is a micronutrient that plays vital roles in various bio-processes in plants and animals. In the present study, a comparative transcriptome analysis associated with physiological indicators was performed to reveal the potential mechanism in different organs in response to zinc toxicity in mulberry. Physiological indicators in mulberry plants treated with increasing concentrations of zinc were monitored to reveal the tolerance limits to zinc concentration. Transcriptome analysis of different organs in mulberry under excess zinc stress was performed to reveal the spatial response to zinc stress. The results show that the hormone signaling pathway and secondary metabolism including lignin biosynthesis, flavonoid biosynthesis and sugar metabolism are important for excess zinc treatment responses. In addition, the organ-based spatial response of these pathways is indicated. Lignin biosynthesis mainly responds to zinc stress in lignified tissues or organs such as stems, flavonoid biosynthesis is the main response to zinc stress in leaves, and sugar metabolism is predominant in roots. Further co-expression network analysis indicated candidate genes involved in the organ-based spatial response. Several transcription factors and genes involved in phenylpropanoid biosynthesis, cell wall biogenesis and sugar metabolism were further validated and designed as organ-based response genes for zinc stress. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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14 pages, 1391 KiB

Open AccessArticle

Effects of Trace Elements on Traits and Functional Active Compounds of Camellia oleifera in Nutrient-Poor Forests

by Qiuyue Dai, Zheng Deng, Lan Pan, Lang Nie, Yunyuan Yang, Yongfang Huang and Jiuxiang Huang

Forests 2023, 14(4), 830; https://doi.org/10.3390/f14040830 - 18 Apr 2023

Cited by 2 | Viewed by 974

Abstract

Camellia oleifera is a major woody oilseed species in China, but it is typically cultivated in nutrient-poor soils and may be affected by various trace elements. This study examined how spraying selenium, boron, and zinc trace elements affected the traits and functional active [...] Read more.

Camellia oleifera is a major woody oilseed species in China, but it is typically cultivated in nutrient-poor soils and may be affected by various trace elements. This study examined how spraying selenium, boron, and zinc trace elements affected the traits and functional active compounds of C. oleifera under nutrient deficiency. The results revealed significant variations in the effects of different trace element combinations on C. oleifera. Optimal concentrations of zinc and selenium are critical for promoting the growth and development of C. oleifera fruit. The transverse diameter of the fruit, the single fruit weight, the number of seeds per fruit, the single fresh seed weight, the oil content in the fruit, and the oil yield per plant of other treatments can be increased by up to 3.07%, 10.57%, 23.66%, 30.23%, 7.94%, and 21.95%, respectively, at most, compared to the control group. Diluting zinc from 1000 to 1500 times and maintaining a selenium concentration from 100 to 200 mg/L has been found to be beneficial for fruit growth. While low concentrations of selenium may promote an increase in fruit transverse diameter, high concentrations of selenium, along with high dilutions of zinc, can have the opposite effect, leading to a reduction in fruit diameter. However, a high concentration of selenium can positively impact the number of seeds per fruit. The most effective combination was found to be a selenium concentration of 0 mg/L, a boron concentration of 4 mg/L, and a zinc dilution of 1500. Interestingly, lower concentrations of selenium and boron, as well as lower dilutions of zinc, were found to increase the oil yield per plant. This suggests that a careful balance of trace elements is required to promote both fruit growth and oil content. The total sterol, squalene, total flavonoid, and polyphenol content of other treatments can be increased by up to 28.81%, 32.07%, 188.04%, and 92.61%, respectively, at most, compared to the control group. Selenium fertilizer and boron fertilizer increased the total sterol content in Camellia oil and had a significant positive correlation at the 0.01 level, but zinc fertilizer had little influence on it. High concentration selenium fertilizer generally increased the squalene, total flavonoid, and polyphenol content in Camellia oil, but boron and zinc fertilizers had little effect on these components. The results suggested that choosing appropriate fertilizer combinations could improve nutrient deficiency in C. oleifera and enhance the functional active compounds of its oil, thereby enhancing its value. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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16 pages, 13192 KiB

Open AccessArticle

Responses of Fine Root Traits and Soil Nitrogen to Fertilization Methods and Nitrogen Application Amounts in a Poplar Plantation

by Xiaoli Yan, Tengfei Dai, Yuan Gao, Nan Di and Liming Jia

Forests 2023, 14(2), 282; https://doi.org/10.3390/f14020282 - 01 Feb 2023

Cited by 1 | Viewed by 1327

Abstract

Inappropriate fertilization management practices have led to low timber production in intensive plantation systems in China. Thus, optimized conventional or advanced fertilization management practices are needed. We aimed to quantify whether optimized furrow fertilization (FF) is comparable to advanced drip fertigation (DF) and [...] Read more.

Inappropriate fertilization management practices have led to low timber production in intensive plantation systems in China. Thus, optimized conventional or advanced fertilization management practices are needed. We aimed to quantify whether optimized furrow fertilization (FF) is comparable to advanced drip fertigation (DF) and to make recommendations regarding fertilization management strategies for poplar plantations. A completely randomized block design experiment with two fertilization methods (DF and FF) and four N application amounts (F₀: 0, F₁: 68, F₂: 113, and F₃: 158 kg N·ha⁻¹·yr⁻¹) was carried out on a Populus × euramericana cv. ‘Guariento’ plantation. Fine root biomass density (FRBD), fine root length density (FRLD), specific root length (SRL), soil total nitrogen (STN), soil inorganic nitrogen (SIN), soil ammonium (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) were measured. The productivity increment was calculated based on tree surveys. The results showed that FRBD and FRLD decreased with the soil depth, and more than 86% was distributed within the 40 cm soil depth. FRBD, FRLD, productivity increment and soil N increased with an increasing amount of N application. DF treatments achieved 117%, 94% and 10% higher FRBD, FRLD and productivity increments, respectively, than did FF treatments. The averages of STN, SIN, NH₄⁺-N and NO₃⁻-N under FF were higher than those under DF, leading to higher concentrations of residual NO₃⁻-N in deep soil. Beneficial management practices for fine root growth were evaluated in the following order: water coupled with N > only N ≥ only water > control. FRBD was positively correlated with the productivity increment. Therefore, fine root extension to increase soil resource absorption yields greater productivity under DF treatments. Drip fertilization is recommended as a better fertilization method to greatly promote the growth of fine roots, as well as productivity and residual lower soil N for poplar plantations. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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16 pages, 16657 KiB

Open AccessArticle

Genome-Wide Identification and Expression Analyses of the PP2C Gene Family in Paulownia fortunei

by Zhenli Zhao, Peiyuan Zhang, Minjie Deng, Yabing Cao and Guoqiang Fan

Forests 2023, 14(2), 207; https://doi.org/10.3390/f14020207 - 21 Jan 2023

Cited by 2 | Viewed by 1358

Abstract

We explored the composition and roles of the protein phosphatase 2C (PP2C) family in Paulownia fortunei. The genome P. fortunei harbored 91 PfPP2C genes, encoding proteins with 120–1107 amino acids (molecular weight range, 13.51–124.81 kDa). The 91 PfPP2Cs were distributed [...] Read more.

We explored the composition and roles of the protein phosphatase 2C (PP2C) family in Paulownia fortunei. The genome P. fortunei harbored 91 PfPP2C genes, encoding proteins with 120–1107 amino acids (molecular weight range, 13.51–124.81 kDa). The 91 PfPP2Cs were distributed in 12 subfamilies, with 1–15 PfPP2Cs per subfamily. The number and types of conserved structure domains differed among PP2Cs, but the distribution of conserved motifs within each subfamily was similar, with the main motif structure being motifs 3, 16, 13, 10, 2, 6, 12, 4, 14, 1, 18, and 8. The PfPP2C genes had 2 to 20 exons. There were ABA-response elements in the promoters of 42 PfPP2C genes, response elements to phytohormones, and stress in the promoters of other PfPP2C genes. A covariance analysis revealed that gene fragment duplication has played an important role in the evolution of the PfPP2C family. There were significant differences in the transcript levels of some PfPP2C genes in P. fortunei affected by witches’ broom (PaWB) and after treatment with rifampicin and methyl methanesulfonate. PfPP2C02, PfPP2C12, PfPP2C19, and PfPP2C80 were strongly related to PaWB. These findings provide a foundation for further studies on the roles of PP2Cs in PaWB. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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12 pages, 3256 KiB

Open AccessArticle

Overexpression of the Poplar WRKY51 Transcription Factor Enhances Salt Tolerance in Arabidopsis thaliana

by Yangyan Zhou, Qing Li and Yue Zhang

Forests 2023, 14(2), 191; https://doi.org/10.3390/f14020191 - 18 Jan 2023

Cited by 5 | Viewed by 1521

Abstract

Salt is a severe environmental stressor that affects growth and development in plants. It is significant to enhance the salt tolerance in plants. In this study, a salt-responsive WRKY transcription factor PtrWRKY51 was isolated from Populus trichocarpa (clone ‘Nisqually-1′). PtrWRKY51 was highly expressed [...] Read more.

Salt is a severe environmental stressor that affects growth and development in plants. It is significant to enhance the salt tolerance in plants. In this study, a salt-responsive WRKY transcription factor PtrWRKY51 was isolated from Populus trichocarpa (clone ‘Nisqually-1′). PtrWRKY51 was highly expressed in mature leaves and root and induced by salt stress. The PtrWRKY51 was overexpressed in Arabidopsis to investigate its biological functions. Compared with Col-0 lines, Overexpressed lines had an increase in germination rate of seed, root length, higher photosynthetic rate, instantaneous leaf WUE, chlorophyll content to improve salt tolerance under salt stress conditions. In contrast, compared to overexpressed and Col-0 lines, the mutant wrky51 was more sensitive to salt stress with lower photosynthetic rate and WUE. Additionally, it was found that the complementary lines (wrky51/ PtrWRKY51) had almost the same salt response as Col-0. In conclusion, PtrWRKY51 is a potential target in the enhancement of poplar tolerance by genetic engineering strategies. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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12 pages, 3924 KiB

Open AccessArticle

by Wuqi Wei, Jinzhi He, Yiwei Luo, Zhen Yang, Xiaoyu Xia, Yuanxiang Han and Ningjia He

Forests 2023, 14(1), 143; https://doi.org/10.3390/f14010143 - 12 Jan 2023

Cited by 2 | Viewed by 1548

Abstract

Root growth regulation plays a crucial role in the acclimatization of plants to their surroundings, but the molecular mechanisms underlying this process remain largely uncertain. Teosinte branched1/cycloidea/proliferating cell factor (TCP) transcription factors are crucial elements linking together plant growth and development, phytohormone signaling, [...] Read more.

Root growth regulation plays a crucial role in the acclimatization of plants to their surroundings, but the molecular mechanisms underlying this process remain largely uncertain. Teosinte branched1/cycloidea/proliferating cell factor (TCP) transcription factors are crucial elements linking together plant growth and development, phytohormone signaling, and stress response. In this study, 15 TCP transcription factors were identified in the mulberry (Morus alba) genome. Gene structure, conserved motif, and phylogenetic analyses revealed the conservation and divergence of these MaTCPs, thus providing insights into their functions. A promoter analysis uncovered distinct numbers and compositions of cis-elements in MaTCP gene promoter regions that may be connected to reproductive growth and phytohormone and stress responses. An expression pattern analysis of the 15 MaTCP genes in mulberry roots indicated that transcriptional levels of MaTCP2, MaTCP4-1, MaTCP8, MaTCP9-1, and MaTCP20-2 are correlated with root development. As revealed by changes in their expressions after drought treatment, these five MaTCP genes are involved in root growth and may increase mulberry tolerance to drought. Our findings lay the foundation for future functional studies of these genes. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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16 pages, 3660 KiB

Open AccessArticle

Grafting with Different Rootstocks Induced DNA Methylation Alterations in Pecan [Carya illinoinensis (Wangenh.) K. Koch]

by Zhuangzhuang Liu, Pengpeng Tan, Youwang Liang, Yangjuan Shang, Kaikai Zhu, Fangren Peng and Yongrong Li

Forests 2023, 14(1), 4; https://doi.org/10.3390/f14010004 - 20 Dec 2022

Cited by 3 | Viewed by 1450

Abstract

Rootstocks are well known to have important effects on scion growth performance. However, the involved mechanisms remain unclear. Recent studies provided some clues on the potential involvement of DNA methylation in grafting, which open up new horizons for exploring how rootstocks induce the [...] Read more.

Rootstocks are well known to have important effects on scion growth performance. However, the involved mechanisms remain unclear. Recent studies provided some clues on the potential involvement of DNA methylation in grafting, which open up new horizons for exploring how rootstocks induce the growth changes. To better understand the involvement of DNA methylation in rootstock-induced growth alterations, whole-genome bisulfite sequencing (WGBS) was used to evaluate the methylation profiles of two sets of pecan grafts with different growth performances on different sizes of rootstocks. The results showed that methylated cytosines accounted for 24.52%–25.60% of all cytosines in pecan. Methylation levels in CG were the highest, with the lowest levels being in CHH (C= cytosine; G= guanine; H = adenine, thymine, or cytosine). Rootstocks induced extensive methylation alterations in scions with 934, 2864, and 15,789 differentially methylated regions (DMRs) determined in CG, CHG, and CHH contexts, respectively. DMR-related genes (DMGs) were found to participate in various processes associated with plant growth, among which 17 DMGs were found, most likely related to hormone response, that may play particularly important roles in graft growth regulation. This study revealed DNA methylomes throughout the pecan genome for the first time, and obtained abundant genes with methylation alterations that were potentially involved in rootstock-induced growth changes in pecan scions, which lays a good basis for further epigenetic studies on pecan and deeper understanding of grafting mechanisms in pecan grafts. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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15 pages, 1987 KiB

Open AccessArticle

Root Development in Cunninghamia lanceolata and Schima superba Seedlings Expresses Contrasting Preferences to Nitrogen Forms

by Haiyan Liang, Lidong Wang, Yanru Wang, Xiaoqiang Quan, Xiaoyu Li, Yaning Xiao and Xiaoli Yan

Forests 2022, 13(12), 2085; https://doi.org/10.3390/f13122085 - 07 Dec 2022

Cited by 4 | Viewed by 1080

Abstract

The inorganic nitrogen (N) that can be absorbed and utilized by plants is mainly ammonium N (NH₄⁺-N) and nitrate N (NO₃⁻-N), which may affect seedlings’ root morphology and growth through its heterogeneous distribution. Root morphology and seedling [...] Read more.

The inorganic nitrogen (N) that can be absorbed and utilized by plants is mainly ammonium N (NH₄⁺-N) and nitrate N (NO₃⁻-N), which may affect seedlings’ root morphology and growth through its heterogeneous distribution. Root morphology and seedling growth were investigated in a subtropical major conifer (Cunninghamia lanceolata) and a broadleaf tree species (Schima superba) under five different NH₄⁺-N to NO₃⁻-N ratios (10:0, 0:10, 7:3, 3:7, 5:5). Results: (1) While both species developed thinner roots under the treatment with a high NO₃⁻-N concentration, the roots of C. lanceolata were longer than those of S. superba. In contrast, the roots of both species were thicker under the treatment with a high NH₄⁺-N concentration, with those in S. superba being much longer than those in C. lanceolata. (2) The mixed NH₄⁺-N and NO₃⁻-N treatments were more conducive to the aboveground growth and biomass accumulation of both tree species and the underground growth of S. superba. N sources with high NO₃⁻-N concentrations were more suitable for underground growth in C. lanceolata seedlings and aboveground growth in S. superba seedlings. Under the N sources with high NH₄⁺-N concentrations, C. lanceolata tended to develop aboveground parts and S. superba tended to develop underground parts. (3) The roots of the two tree species adopted the expansion strategy of increasing the specific root length and reducing the root tissue density under the N sources with high NO₃⁻-N concentrations but the opposite with high NH₄⁺-N concentrations. The root-to-shoot ratio of C. lanceolata increased under high NO₃⁻-N concentrations, while that of S. superba increased under high NO₃⁻-N concentrations. These results indicate that the responses of root morphology to different N forms are species-specific. Furthermore, according to the soil’s N status, NH₄⁺-N can be appropriately applied to C. lanceolata and NO₃⁻-N to S. superba for cultivating seedlings. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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13 pages, 1799 KiB

Open AccessArticle

In Situ Rainwater Collection and Infiltration System Alleviates the Negative Effects of Drought on Plant-Available Water, Fine Root Distribution and Plant Hydraulic Conductivity

by Changkun Ma, Haobo Meng, Biao Xie, Qian Li, Xiangdong Li, Beibei Zhou, Quanjiu Wang and Yi Luo

Forests 2022, 13(12), 2082; https://doi.org/10.3390/f13122082 - 07 Dec 2022

Cited by 2 | Viewed by 1084

Abstract

Soil water status and fine-root characteristics are the foundation for implementing forest water-management strategies in semiarid forest plantations, where rainwater is always the sole source of water for plant growth. Rainwater management and utilization are effective strategies to alleviate water scarcity in semiarid [...] Read more.

Soil water status and fine-root characteristics are the foundation for implementing forest water-management strategies in semiarid forest plantations, where rainwater is always the sole source of water for plant growth. Rainwater management and utilization are effective strategies to alleviate water scarcity in semiarid areas as ground water is always inaccessible there. Through the implementation of an in situ rainwater collection and infiltration system (IRCIS), we investigated the effects of IRCIS on soil water and fine-root distributions in the 0–5 m soil profile in a wet (2015, 815 mm) and a dry year (2016, 468 mm) in rainfed Robinia pseudoacacia forests in the Loess Plateau region of China. The results showed drought significantly decreased plant water availability and hydraulic conductivity of roots and branches, but strongly increased soil moisture deficits and fine-root (<2 mm diameter) biomass. With the implementation of IRCIS, soil profile available water and plant hydraulic conductivity can be significantly increased, but soil moisture deficits and fine-root (<2 mm diameter) biomass can be significantly decreased. Drought also significantly influenced the root distribution of Robinia pseudoacacia. The maximum depth of Robinia pseudoacacia roots in the dry year was significantly greater than in the wet year. Therefore, Robinia pseudoacacia can absorb shallow (0–1.5 m) soil water in wet years, while utilizing deep (>1.5 m) soil water in dry years to maintain normal growth and resist drought stress. The results of this study will contribute to the formulation of appropriate strategies for planning and managing rainwater resources in forest plantations. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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15 pages, 3062 KiB

Open AccessArticle

The Influence of Iron Application on the Growth and Cadmium Stress Tolerance of Poplar

by Mingwan Li, Changrui Liu, Dangquan Zhang, Bingwen Wang and Shen Ding

Forests 2022, 13(12), 2023; https://doi.org/10.3390/f13122023 - 29 Nov 2022

Cited by 3 | Viewed by 1265

Abstract

There is a complex cadmium (Cd) and iron (Fe) interaction in soil. To explore the influences of Fe application on the growth, Cd accumulation, and antioxidant capacity of poplar under Cd exposure, Populus tremula × P. alba ‘717’ was treated with different concentrations [...] Read more.

There is a complex cadmium (Cd) and iron (Fe) interaction in soil. To explore the influences of Fe application on the growth, Cd accumulation, and antioxidant capacity of poplar under Cd exposure, Populus tremula × P. alba ‘717’ was treated with different concentrations of Cd (0 and 100 μM) and Fe (50 and 150 μM). In addition, the root architecture, leaf chlorophyll content, Cd accumulation, and antioxidant enzyme activity were analyzed. The results showed that the high-dose Fe (150 μM) did not change poplar biomass in zero-Cd treatment but increased the chlorophyll content, total root surface area, net photosynthetic rate, and biomass accumulation of Cd-stressed poplar. In addition, under Cd stress, high-dose Fe increased the translocation factor (TF) of Cd, decreased root and leaf malondialdehyde (MDA) content, and enhanced root and leaf SOD activity. That is, high-dose Fe could alleviate the suppression of Cd on the growth of poplar and enhance the transport of Cd to aboveground tissues and the SOD activity in roots and leaves, thus alleviating the Cd-induced oxidative stress. This study will provide reference for the remediation of Cd-contaminated soils using poplar. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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17 pages, 3619 KiB

Open AccessArticle

Complete Genome Expression Analysis of the Auxin Response Factor Gene Family in Sandalwood and Their Potential Roles in Drought Stress

by Xiaojing Liu, Yunshan Liu, Shengkun Wang, Fangcuo Qin, Dongli Wang, Yu Chen, Lipan Hu, Sen Meng and Junkun Lu

Forests 2022, 13(11), 1934; https://doi.org/10.3390/f13111934 - 16 Nov 2022

Cited by 3 | Viewed by 1437

Abstract

Auxin response factors (ARFs) are essential transcription factors in plants that play an irreplaceable role in controlling the expression of auxin response genes and participating in plant growth and stress. The ARF gene family has been found in Arabidopsis thaliana, apple ( [...] Read more.

Auxin response factors (ARFs) are essential transcription factors in plants that play an irreplaceable role in controlling the expression of auxin response genes and participating in plant growth and stress. The ARF gene family has been found in Arabidopsis thaliana, apple (Malus domestica), poplar (Populus trichocarpa) and other plants with known whole genomes. However, S. album (Santalum album L.), has not been studied. In this study, we analyzed and screened the whole genome of S. album and obtained 18 S. album ARFs (SaARFs), which were distributed on eight chromosomes. Through the prediction of conserved domains, we found that 13 of the 18 SaARFs had three intact conserved domains, named DBD, MR, Phox and Bem1 (PB1), while the extra five SaARFs (SaARF3, SaARF10, SaARF12, SaARF15, SaARF17) had only two conserved domains, and the C-terminal PB1 domain was missing. By establishing a phylogenetic tree, 62 ARF genes in S. album, poplar and Arabidopsis were divided into four subgroups, named Ⅰ, Ⅱ, Ⅲ and Ⅳ. According to the results of collinearity analysis, we found that ten of the eighteen ARF genes were involved in five segmental duplication events and these genes had short distance intervals and high homology in the SaARF gene family. Finally, tissue-specific and drought-treatment expression of SaARF genes was observed by quantitative real-time polymerase chain reaction (qRT-PCR), and six genes were significantly overexpressed in haustorium. Meanwhile we found SaARF5, SaARF10, and SaARF16 were significantly overexpressed under drought stress. These results provide a basis for further analysis of the related functions of the S. album ARF gene and its relationship with haustorium formation. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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13 pages, 2234 KiB

Open AccessArticle

Foliar Application of Selenium Reduces Cadmium Accumulation in Walnut Seedlings

by Bingwen Wang, Dangquan Zhang, Wenfeng Wang, Yukun Song, Mengfei Lu and Shen Ding

Forests 2022, 13(9), 1493; https://doi.org/10.3390/f13091493 - 15 Sep 2022

Cited by 2 | Viewed by 1158

Abstract

Cadmium (Cd) and selenium (Se) could jointly affect plant growth. To investigate the affect of Se on the Cd accumulation in Juglans regia and the physiological mechanism by which Se regulates Cd-induced oxidative stress, in this study, the effects of different foliar application [...] Read more.

Cadmium (Cd) and selenium (Se) could jointly affect plant growth. To investigate the affect of Se on the Cd accumulation in Juglans regia and the physiological mechanism by which Se regulates Cd-induced oxidative stress, in this study, the effects of different foliar application doses of Se (0 (Se0), 20 (Se20), and 200 (Se200) μM) on J. regia (variety Xinfeng) seedlings under Cd stress (5 mM) were determined. The results show that exogenous application of Se (Se20 and Se200) increased walnut biomass compared with Se0 under Cd stress. Under Cd stress, exogenous application of 20 μM Se increased the catalase (CAT), peroxidase (POD), and ascorbate oxidase (AAO) activities in walnut roots and the CAT and AAO activities in walnut leaves, and exogenous application of 200 μM Se increased the CAT, POD, and AAO activities in walnut roots. Furthermore, under Cd stress, exogenous application of 20 and 200 μM Se both decreased the contents of superoxide (O₂^•−), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) in walnut roots and the content of MDA in walnut leaves. Moreover, application of 20 and 200 μM Se both reduced the accumulation of Cd in the root, wood, bark, and leaves of walnuts, and application of 200 μM Se enhanced Se concentration in the root, wood, bark, and leaves. Overall, exogenous application of Se, especially 200 μM Se, could reduce Cd accumulation and enhance CAT, POD, and AAO activities in Cd-stressed walnut roots, thus alleviating Cd stress. This study provides technical guidance for reducing the effects of Cd stress on walnut growth. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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26 pages, 7693 KiB

Open AccessArticle

Analysis of the NAC Gene Family in Salix and the Identification of SpsNAC005 Gene Contributing to Salt and Drought Tolerance

by Haifeng Yang, Lijiao Fan, Xingwang Yu, Xinqian Zhang, Pu Hao, Dongshan Wei and Guosheng Zhang

Forests 2022, 13(7), 971; https://doi.org/10.3390/f13070971 - 21 Jun 2022

Cited by 3 | Viewed by 1710

Abstract

The NAC gene family is of great value for plant stress resistance and development. In this study, five NAC genes with a typical NAM domain were isolated from Salix psammophila, which is a stress-resistant willow endemic to western China. Two hundred sixty-two [...] Read more.

The NAC gene family is of great value for plant stress resistance and development. In this study, five NAC genes with a typical NAM domain were isolated from Salix psammophila, which is a stress-resistant willow endemic to western China. Two hundred sixty-two NAC genes from Salix psammophila, Salix purpurea, and Arabidopsis were used to construct the phylogenetic tree to examine the phylogenetic relationship. Five NAC genes in Salix psammophila were the focus of bioinformatics analysis and conserved structural domain analysis. The SpsNAC005 gene was overexpressed in Populus hopeiensis, and the transgenic lines were subjected to salt and simulated drought stress to analyze their phenotype changes and tolerance to stress. The results showed that transgenic poplar height and leaf area increased by 29.73% and 76.36%, respectively, compared with those of wild-type plants. Under stress treatment, the height growth rates and ground diameter growth rates of the transgenic lines were significantly higher than those of the wild-type, whereas their fresh weight and dry weight were decreased compared to those of the wild-type. The SOD activities, POD activities, and Pro contents of the transgenic plants were significantly increased, and the accumulation of MDA was significantly lower than that in the wild-type, and the transgenic lines showed clear tolerance to salt and drought. The expressions of the SOS1, MPK6, HKT1, and P5CS1 genes were downregulated in the transgenic lines. The expression of the PRODH1 gene was downregulated in the transgenic lines. These results indicate that overexpression of the SpsNAC005 gene in transgenic plants can promote plant growth and development and improve tolerance to salt and drought. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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14 pages, 4854 KiB

Open AccessArticle

Chemical Compositions of Walnut (Juglans Spp.) Oil: Combined Effects of Genetic and Climatic Factors

by Hanbo Yang, Xu Xiao, Jingjing Li, Fang Wang, Jiaxuan Mi, Yujie Shi, Fang He, Lianghua Chen, Fan Zhang and Xueqin Wan

Forests 2022, 13(6), 962; https://doi.org/10.3390/f13060962 - 20 Jun 2022

Cited by 11 | Viewed by 2106

Abstract

Walnut oil is a high-value oil product. Investigation of the variation and the main climatic factors affecting the oil’s chemical composition is vital for breeding and oil quality improvement. Therefore, the fatty acid, micronutrients, and secondary metabolites compositions and contents in walnut oil [...] Read more.

Walnut oil is a high-value oil product. Investigation of the variation and the main climatic factors affecting the oil’s chemical composition is vital for breeding and oil quality improvement. Therefore, the fatty acid, micronutrients, and secondary metabolites compositions and contents in walnut oil were determined in three species: Juglans regia L. (common walnut), J. sigillata Dode (iron walnut), and their hybrids (Juglans sigillata Dode × J. regia L.), which were cultivated aat different sites. The major fatty acids were linoleic (51.39–63.12%), oleic (18.40–33.56%), and linolenic acid (6.52–11.69%). High variation in the contents of fatty acids, micronutrients, and secondary metabolites was found between both species and sites. Interestingly, myristic, margaric, and margaroleic acid were only detected in the hybrids’ walnut oil, yet α-tocopherol was only detected in common and iron walnut oil. Climatic factors significantly affected the composition and content of fatty acid, whereas δ-tocopherol was mostly dependent on the genetic factors. The average relative humidity explained the most variation in the fatty acids, micronutrients, and secondary metabolites, which showed a significant positive and negative effect on the monounsaturated fatty acids and polyunsaturated fatty acids, respectively. These findings contribute to the provision of better guidance in matching sites with walnut trees, and improvement of the nutritional value of walnut oil. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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19 pages, 4205 KiB

Open AccessFeature PaperArticle

Water Uptake and Hormone Modulation Responses to Nitrogen Supply in Populus simonii under PEG-Induced Drought Stress

by Zhen Li, Xiaoling Wang, Yunshan Liu, Yangyan Zhou, Zhiliang Qian, Zequn Yu, Na Wu and Zhan Bian

Forests 2022, 13(6), 907; https://doi.org/10.3390/f13060907 - 10 Jun 2022

Cited by 6 | Viewed by 1755

Abstract

In the present study, the effects of nitrogen (N) supply on water uptake, drought resistance, and hormone regulation were investigated in Populus simonii seedlings grown in hydroponic solution with 5% polyethylene glycol (PEG)-induced drought stress. While acclimating to drought, the P. simonii seedlings [...] Read more.

In the present study, the effects of nitrogen (N) supply on water uptake, drought resistance, and hormone regulation were investigated in Populus simonii seedlings grown in hydroponic solution with 5% polyethylene glycol (PEG)-induced drought stress. While acclimating to drought, the P. simonii seedlings exhibited a reduction in growth; differential expression levels of aquaporins (AQPs); activation of auxin (IAA) and abscisic acid (ABA) signaling pathways; a decrease in the net photosynthetic rate and transpiration rate; and an increase in stable nitrogen isotope composition (δ¹⁵N), total soluble substances, and intrinsic water use efficiency (WUEi), with a shift in the homeostasis of reactive oxygen species (ROS) production and scavenging. A low N supply (0.01 mM NH₄NO₃) or sufficient N supply (1 mM NH₄NO₃) exhibited distinct morphological, physiological, and transcriptional responses during acclimation to drought, primarily due to strong responses in the transcriptional regulation of genes encoding AQPs; higher soluble phenolics, total N concentrations, and ROS scavenging; and lower transpiration rates, IAA content, ABA content, and ROS accumulation with a sufficient N supply. P. simonii can differentially manage water uptake and hormone modulation in response to drought stress under deficient and sufficient N conditions. These results suggested that increased N may contribute to drought tolerance by decreasing the transpiration rate and O₂⁻ production while increasing water uptake and antioxidant enzyme activity. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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16 pages, 2417 KiB

Open AccessArticle

Screening of Key Indices and the Gene Transcriptional Regulation Analysis Related to Salt Tolerance in Salix matsudana Seedlings

by Yuanxiang Pang, Longmei Guo, Tiantian Wang, Wei Liu, Peili Mao, Xiaonan Cao, Ying Geng and Banghua Cao

Forests 2022, 13(5), 754; https://doi.org/10.3390/f13050754 - 13 May 2022

Cited by 2 | Viewed by 1632

Abstract

Pot experiments were performed to comparatively study the differences in 16 salt tolerance indices between the seedlings of six Salix matsudana clones under the stress of various concentrations of NaCl (0, 0.1%, 0.3%, 0.5%, and 0.7%), including the salt injury index, shoot fresh [...] Read more.

Pot experiments were performed to comparatively study the differences in 16 salt tolerance indices between the seedlings of six Salix matsudana clones under the stress of various concentrations of NaCl (0, 0.1%, 0.3%, 0.5%, and 0.7%), including the salt injury index, shoot fresh weight, root fresh weight, leaf water content, relative conductivity, malondialdehyde content, and antioxidant enzyme activity. The salt-tolerant clones and key indices of salt tolerance were selected. Transcriptome sequencing analysis was performed on the selected salt-tolerant and salt-sensitive clones under salt stress, and the links between the physiological indices of salt tolerance and gene expression were analyzed. Results: (1) Superoxide dismutase (SOD), peroxidase (POD), chlorophyll, and net photosynthetic rate were closely related to the salt tolerance of Salix matsudana at the seedling stage. The regression equation was constructed as follows: salt tolerance index (y) = 0.224x₁₀ + 0.216x₁₁ + 0.127x₁₂ + 0.191x₇ − 0.187 (x₁₀ = chlorophyll, x₁₁ = SOD, x₁₂ = POD, x₇ = net photosynthetic rate). (2) The number of differentially expressed genes between the seedlings of salt-tolerant and salt-sensitive clones varied with the time of exposure (0 h, 4 h, 12 h, and 24 h) to 200 mmol·L⁻¹ NaCl stress. The most differentially expressed genes in Sm172 were detected upon 24 h vs. 4 h of salt treatment, while the most in Sm6 were in the 24 h vs. 0 h comparison. Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes analysis showed that several differentially expressed genes were involved in carotenoid biosynthesis and plant mitogen-activated protein kinase signaling pathways. The nine highly expressed transcription factor genes (Sm172-f2p30-2392, Sm172-f2p28-2386, Sm6-f8p60-2372, Sm6-f2p39-2263, Sm6-f16p60-2374, Sm6-f3p60-931, Sm6-f2p60-1067, Sm172-f3p54-1980, and Sm172-f3p54-1980) were closely correlated with the four key indices of salt tolerance. These genes could become genetic resources for salt tolerance breeding of Salix matsudana. Full article

(This article belongs to the Special Issue Strategies for Tree Improvement under Stress Conditions)

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