The natural environment of crops is exposed to a complex collection of biotic and abiotic pressures. Abiotic stresses cover a diversity of environmental elements that cannot be avoided, such as temperature, drought, salinity, cold, heat, light, and water stress. Biotic stress is caused by living organisms with which plants coexist and interact. Pathogens and herbivores are examples of biotic stressors that can threaten food security and result in significant economic losses. Agricultural production systems differ in the extent of stress towards cultivated crops; agroforestry is considered to provide a protective function against environmental stress. The concept of this review was to assess the impact of environmental change and the atmospheric variability on the plants in agroforestry systems. The application of trees in field crop production has become more and more involved in practice, especially in areas with an extreme climate and unfavorable soil conditions. The main reasons for the rising interest are the effects of climate change, soil degradation, and erosion. Most of the trees are used as hedgerows or farm boundaries, or as scattered planting on the farm to control soil erosion as well as to improve farm productivity, which requires a thorough understanding of each stress element.

/pdf/conceptualizing-multiple-stressors-and-their-consequences-in-3bklt52g.pdf

Conceptualizing Multiple Stressors and Their Consequences in Agroforestry Systems

Drought stress inducing pollen sterility can reduce crop yield worldwide. The regulatory crosstalk associated with the effects of drought on pollen formation at the cellular level has not been explored in detail so far. In this study, we performed morphological and cytoembryological analysis of anther perturbations and examined pollen development in two spring barley genotypes that differ in earliness and drought tolerance. The Syrian breeding line CamB (drought-tolerant) and the European cultivar Lubuski (drought-sensitive) were used as experimental materials to analyze the drought-induced changes in yield performance, chlorophyll fluorescence kinetics, the pollen grain micromorphology and ultrastructure during critical stages of plant development. In addition, fluctuations in HvGAMYB expression were studied, as this transcription factor is closely associated with the development of the anther. In the experiments, the studied plants were affected by drought, as was confirmed by the analyses of yield performance and chlorophyll fluorescence kinetics. However, contrary to our expectations, the pollen development of plants grown under specific conditions was not severely affected. The results also suggest that growth modification, as well as the perturbation in light distribution, can affect the HvGAMYB expression. This study demonstrated that the duration of the vegetation period can influence plant drought responses and, as a consequence, the processes associated with pollen development as every growth modification changes the dynamics of drought effects as well as the duration of plant exposition to drought.

/pdf/the-effects-of-growth-modification-on-pollen-development-in-t3j7kzak.pdf

The Effects of Growth Modification on Pollen Development in Spring Barley (Hordeum vulgare L.) Genotypes with Contrasting Drought Tolerance

Gandarusa (Justicia gendarussa Burm. F.) is a shrub used in herbal medicine, but knowledge of optimal cultivation methods for enhancing plant growth and metabolite yield is limited. This research aimed to evaluate the effect of shading and nitrogen fertilizer on the growth, photosynthetic parameters, and total sugar content of gandarusa. A split-plot experimental design was used with shading (S) (0% (S0), 25% (S25), and 50% (S50)) as the main plots and nitrogen fertilizer (N) (0 (N0), 90 (N90), 180 (N180), and 270 (N270) kg ha-1) as the subplots. The results showed that the combination of S0 and N270 was the most effective treatment for plant growth, indicated by the highest values of plant height and the number of leaves and branches. It also yielded high sugar content, with a value range of 72-76 mg g-1 leaves wet weight. The combination of S0 and N0 produced the highest photosynthetic rate (Pn) in the plant at 23.91 mol CO2 m-2 s-1, and total chlorophyll content was highest with S25 and N270. Based on the results, shading decreased Pn, sugar production, and growth of gandarusa, while nitrogen fertilizer enhanced them. However, there was no interaction between shading and fertilizer on sugar production and growth of gandarusa, except for Pn.

/pdf/effects-of-shading-and-nitrogen-fertilizer-on-growth-and-280ey68p.pdf

Effects of Shading and Nitrogen Fertilizer on Growth and Physiology of Gandarusa (Justicia gendarussa Burm. F.)

Magnolia sinostellata is one of the endangered species in China and largely suffers light deficiency stress in the understory of forest. However, the weak light response molecular mechanism remains unclear. More importantly, hub genes in the molecular network have not been pinpointed. To explore potential regulators in the mechanism, weighted gene co-expression network analysis (WGCNA) was performed to analysis the trancriptome data of M. sinostellata leaves subjected to weak light with different time points. Gene co-expression analysis illustrated that module 1, 2 and 3 were closely associated with light deficiency treatment, which. Gene ontology and KEGG analyses showed that genes in module 1 mainly participated in amino and nucleotide metabolism, module 2 mostly involved in carbon fixation and module 3 mostly regulated photosynthesis related pathways, among which 6, 7 and 8 hub genes were identified, respectively. Hub genes isoform_107196 in module 1 and isoform_55976 in module 2 were unique to M. sinostellata. This study found that light deficiency inhibited photosynthesis and stress tolerance, while improved carbon metabolism and flowering related pathways in M. sinostellata, which can impact its accumulation reserves of growth and reproduction in the next season. In addition, key shade response regulators identified in this study have laid a firm foundation for further investigation of shade response molecular mechanism and protection of other shade sensitive plants. 

/pdf/identification-of-potential-light-deficiency-response-m0r954ru.pdf

Identification of potential light deficiency response regulators in endangered species Magnolia sinostellata

Species of the Magnoliaceae family are valued for their ornamental qualities and are widely used in landscaping worldwide. However, many of these species are endangered in their natural environments, often due to being overshadowed by overstory canopies. The molecular mechanisms of Magnolia’s sensitivity to shade have remained hitherto obscure. Our study sheds light on this conundrum by identifying critical genes involved in governing the plant’s response to a light deficiency (LD) environment. In response to LD stress, Magnolia sinostellata leaves were endowed with a drastic dwindling in chlorophyll content, which was concomitant to the downregulation of the chlorophyll biosynthesis pathway and upregulation in the chlorophyll degradation pathway. The STAY-GREEN (MsSGR) gene was one of the most up-regulated genes, which was specifically localized in chloroplasts, and its overexpression in Arabidopsis and tobacco accelerated chlorophyll degradation. Sequence analysis of the MsSGR promoter revealed that it contains multiple phytohormone-responsive and light-responsive cis-acting elements and was activated by LD stress. A yeast two-hybrid analysis resulted in the identification of 24 proteins that putatively interact with MsSGR, among which eight were chloroplast-localized proteins that were significantly responsive to LD. Our findings demonstrate that light deficiency increases the expression of MsSGR, which in turn regulates chlorophyll degradation and interacts with multiple proteins to form a molecular cascade. Overall, our work has uncovered the mechanism by which MsSGR mediates chlorophyll degradation under LD stress conditions, providing insight into the molecular interactions network of MsSGR and contributing to a theoretical framework for understanding the endangerment of wild Magnoliaceae species.

/pdf/stay-green-accelerates-chlorophyll-degradation-in-magnolia-9h8f6478.pdf

STAY-GREEN Accelerates Chlorophyll Degradation in Magnolia sinostellata under the Condition of Light Deficiency

The endangered plant Magnolia sinostellata largely grows in the understory of forest and suffers light deficiency stress. It is generally recognized that the interaction between plant development and growth environment is intricate; however, the underlying molecular regulatory pathways by which light deficiency induced growth inhibition remain obscure. To understand the physiological and molecular mechanisms of plant response to shading caused light deficiency, we performed photosynthesis efficiency analysis and comparative transcriptome analysis in M. sinostellata leaves, which were subjected to shading treatments of different durations. Most of the parameters relevant to the photosynthesis systems were altered as the result of light deficiency treatment, which was also confirmed by the transcriptome analysis. Gene Ontology and KEGG pathway enrichment analyses illustrated that most of differential expression genes (DEGs) were enriched in photosynthesis-related pathways. Light deficiency may have accelerated leaf abscission by impacting the photosynthesis efficiency and hormone signaling. Further, shading could repress the expression of stress responsive transcription factors and R-genes, which confer disease resistance. This study provides valuable insight into light deficiency-induced molecular regulatory pathways in M. sinostellata and offers a theoretical basis for conservation and cultivation improvements of Magnolia and other endangered woody plants.

Light Deficiency Inhibits Growth by Affecting Photosynthesis Efficiency as well as JA and Ethylene Signaling in Endangered Plant Magnolia sinostellata.

Mingjie Ren

Papers

Light Deficiency Inhibits Growth by Affecting Photosynthesis Efficiency as well as JA and Ethylene Signaling in Endangered Plant Magnolia sinostellata.