Root system response in Argania spinosa plants under drought stress and recovery

Short-term severe drought influences root volatile biosynthesis in eastern white pine (Pinus strobus L)

Climate change-related drought stress is expected to shift carbon partitioning toward volatile organic compound (VOC) biosynthesis. The effect of drought stress on VOC synthesis remains unknown in several tree species. Therefore, we exposed eastern white pine (Pinus strobus) plants to severe drought for 32 days and performed physiological analysis (chlorophyll content, leaf water content, and root/shoot index), biochemical analysis (non-structural carbohydrates, proline, lipid peroxidation, and antioxidant assay), and total root VOC analysis. Drought stress decreased the relative water and soil moisture contents. Root proline accumulation and antioxidant activity increased significantly, whereas leaf chlorophyll synthesis and fresh weight decreased significantly in drought-treated plants. A non-significant increase in sugar accumulation (leaves and roots), proline accumulation (leaves), antioxidant activity (leaves), and lipid peroxidation (leaves and roots) was observed in drought-treated plants. Drought stress caused a non-significant decline in root/shoot ratio and starch accumulation (leaves and roots) and caused a significant increase in root abscisic acid content. Drought-treated plants showed an increase in overall monoterpene synthesis (16%) and decline in total sesquiterpene synthesis (3%). Our findings provide an overall assessment of the different responses of VOC synthesis to severe water deficit that may help unravel the molecular mechanisms underlying drought tolerance in P. strobus.

TaPYL4, an ABA receptor gene of wheat, positively regulates plant drought adaptation through modulating the osmotic stress-associated processes

BACKGROUND

Abscisic acid receptors (ABR) involve transduction of the ABA signaling in plants, impacting largely on stress-defensive physiological processes and plant osmotic stress response. In this study, we characterized TaPYL4, a gene of ABR family in T. aestivum, in mediating plant drought tolerance given scarcity of functional characterization on wheat ABR members thus far.

RESULTS

TaPYL4 harbors nine conserved domains shared by its PYL counterparts, targeting onto plasma membrane and nucleus after endoplasmic reticulum assortment. TaPYL4 interacts with TaPP2C2 whereas the latter with TaSnRK2.1, which establish a core module of the ABA signaling pathway. TaPYL4 expression was upregulated in root and aerial tissues upon drought stress. Overexpressing TaPYL4 conferred plants improved growth traits whereas knockdown expression of target gene alleviated growth feature compared with wild type under drought treatment. The TaPYL4-enhanced drought adaptation associates gene function in positively regulating stomata movement, osmolyte biosynthesis, and root system architecture (RSA) establishment. Expression analysis on the P5CS family genes involving proline biosynthesis indicated that TaP5CS1 exerts critical roles in promoting osmolytes accumulation in drought-challenged TaPYL4 lines. TaPIN9, a PIN-FORMED gene modulating cellular auxin translocation, was validated to function as a crucial mediator in defining RSA establishment underlying TaPYL4 regulation. Transcriptome analysis revealed that TaPYL4 controls transcription of numerous genes, which impact on physiological processes associated with 'biological process', 'molecular component', and 'cellular process'. Moreover, the differentially expressed genes mediated by TaPYL4 were closely related to stress defensive pathways.

CONCLUSIONS

Our investigation suggested that TaPYL4 acts as a positive regulator in plant drought tolerance and a valuable target for engineering drought-tolerant cultivars in T. aestivum.

Limited Acclimation in Leaf Morphology and Anatomy to Experimental Drought in Temperate Forest Species

Simple Summary

Climate change shown to have a significant impact on the forest ecosystem due to increased and more frequent occurrence of extreme drought. However, in order to successfully adjust to the xeric environments, plants can usually adopt a variety of adaptation strategies. Here, we investigated the morpho-anatomical traits and biomass allocation patterns as acclimation mechanisms in drought conditions. We found that the interrelation between leaf morphological and anatomical traits were equally affected by drought conditions across all species. This suggests that there is no convincing evidence to classify taxa based on drought resistance vs. drought tolerance. However, based on the biomass allocation pattern, we found that P. koraiensis and F. mandshurica had the higher RMF and total PB, but lower LFM, suggesting higher drought tolerance than those of the other species. Therefore, our dataset revealed some easily measurable traits, such as LMF, RMF, and PB, which demonstrated the seedling’s ability to cope with drought and which could be utilized to choose drought-tolerant species for reforestation in the temperate forest.

Abstract

Drought is a critical and increasingly common abiotic factor that has impacts on plant structures and functioning and is a challenge for the successful management of forest ecosystems. Here, we test the shifts in leaf morpho-anatomical or hydraulic traits and plant growth above ground caused by drought. A factorial experiment was conducted with two gymnosperms (Larix gmelinii and Pinus koraiensis) and two angiosperms (Fraxinus mandshurica and Tilia amurensis), tree species grown under three varying drought intensities in NE China. Considering all the species studied, the plant height (PH), root collar diameter (RCD), and plant biomass (PB) were significantly decreased by drought. The leaf thickness (LT) increased, while the leaf area (LA) decreased with drought intensity. In the gymnosperms, the mesophyll thickness (MT) increased, and the resin duct decreased, while in the angiosperms the palisade mesophyll thickness (PMT), the spongy mesophyll thickness (SMT), and the abaxial (ABE) and adaxial epidermis (ADE) thickness were increased by drought. The correlation analysis revealed that P. koraiensis and F. mandshurica had the higher RMF and total plant biomass, but the least LMF, suggesting drought tolerance. In contrast, the L. gmelinii had the least RMF and higher LMF, suggesting vulnerability to drought. Similarly, T. amurensis had the higher leaf size, which increased the evaporative demand and depleted the soil water quickly relative to the other species. The interrelation among the morpho-anatomical leaf traits was equally affected by drought across all the studied species, suggesting that there is no clear evidence to differentiate the taxa based on drought resistance vs. drought tolerance. Thus, we have identified some easily measurable traits (i.e., LMF, RMF, and PB) which evidenced the seedling’s ability to cope with drought and which therefore could be used as proxies in the selection of drought tolerant species for reforestation in the temperate forest.

RNA-Seq Analysis Demonstrates Different Strategies Employed by Tiger Nuts (Cyperus esculentus L.) in Response to Drought Stress

Drought stress, an important abiotic stress, has affected global agricultural production by limiting the yield and the quality of crops. Tiger nuts (Cyperus esculentus L.) are C4 crops in the Cyperaceae family, which have high-quality wholesome ingredients. However, data on mechanisms underlying the response of tiger nuts to drought stress are few. Here, the variety of Jisha 1 and 15% polyethylene glycol (PEG; a drought stress simulator) were used to study the mechanisms of stress response in tiger nuts. Our evaluation of the changes in physiological indicators such as electrolyte leakage (El), malondialdehyde (MDA), hydrogen peroxide (H₂O₂), superoxide anion (O₂⁻) and activities of reactive oxygen species (ROS) showed that 12 h was the most suitable time point to harvest and analyze the response to drought stress. Thereafter, we performed transcriptome (RNA-Seq) analysis in the control (CK) and stress treatment groups and showed that there was a total of 1760 differentially expressed genes (DEGs). Gene Ontology (GO) analysis showed that the DEGs were enriched in abscisic acid (ABA) terms, and pathways such as starch and sucrose metabolism (ko00500), phenylpropanoid biosynthesis (ko00940) and plant hormone signal transduction (ko04075) were significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. In addition, quantitative real-time PCR (qRT-PCR) analysis of the DEGs demonstrated an upregulation of ABA and lignin content, as well as enzyme activities in enriched pathways, which validated the RNA-Seq data. These results revealed the pathways and mechanisms adopted by the tiger nuts in response to drought stress.

Agro-Fruit-Forest Systems Based on Argan Tree in Morocco: A Review of Recent Results

The argan tree, Argania spinosa (L.) Skeels, is a horticultural forestry species characterized by its endemicity and adaptation to arid and semi-arid zones in the southwest of Morocco. Despite its limited geographical distribution, argan tree presents large genetic diversity, suggesting that improvement of argan is possible. This species plays important ecological, and socioeconomic roles in the sustainable development of the country. The integration of arganiculture into Moroccan agricultural policy has been implemented through a sector strategy, which is fully aligned with the conservation and regeneration of argan forest. A. spinosa is suitable for incorporation into different agroforestry productive systems under agro-fruit-forest model and its domestication will provide a powerful means of socio-economic and environmental management. Here, we provide an overview of the argan tree literature and highlight the specific aspects of argan stands, as agro-forest systems, with the aim of developing an adequate strategy of conservation and domestication of this species. We introduce promising programs and projects for argan plantations and arganiculture, which have been adopted to relieve anthropogenic pressure on the natural argan forest.