Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

https://hal.archives-ouvertes.fr/hal-00886451/document

Plant drought stress: effects, mechanisms and management

Abiotic stresses are one of the major constraints to crop production and food security worldwide. The situation has aggravated due to the drastic and rapid changes in global climate. Heat and drought stress are undoubtedly the two most important stresses having huge impact on growth and productivity of the crops. It is very important to understand the physiological, biochemical and ecological interventions related to these stresses for better management. A wide range of plant responses to these stresses could be generalized into morphological, physiological and biochemical responses. Interestingly, this review provides a detailed account of plant responses to heat and drought stresses with special focus on highlighting the commonalities and differences. Crop growth and yields are negatively affected by sub-optimal water supply and abnormal temperatures due to physical damages, physiological disruptions and biochemical changes. Both these stresses have multi-lateral impacts and therefore, complex in mechanistic action. A better understanding of plant responses to these stresses has pragmatic implication for remedies and management. A comprehensive account of conventional as well as modern approaches to deal with heat and drought stresses have also been presented here. A side-by-side critical discussion on salient responses and management strategies for these two important abiotic stresses provides a unique insight into the phenomena. A holistic approach taking into account the different management options to deal with heat and drought stress simultaneously could be a win-win approach in future.

/pdf/crop-production-under-drought-and-heat-stress-plant-4citjxbeya.pdf

Crop Production under Drought and Heat Stress: Plant Responses and Management Options

Abiotic stresses such as drought, high salinity, and cold are common adverse environmental conditions that significantly influence plant growth and productivity worldwide. The phytohormone abscisic acid (ABA) plays an important role in physiological and developmental responses as well as in co-ordinating various stress signal transduction pathways in plants. DREBs (dehydration responsive element binding) are important plant transcription factors (TFs) that regulate the expression of many stress-inducible genes mostly in an ABA-independent manner and play a critical role in improving the abiotic stress tolerance of plants by interacting with a DRE/CRT cis-element present in the promoter region of various abiotic stress-responsive genes. This review summarizes recent studies highlighting the role of the DRE-binding family of TFs in the adaptive responses to different abiotic stresses and their structural and functional characters with emphasis on the expression and regulation of DREBs. The practical and application value of DREBs in crop improvement, such as stress tolerance engineering as well as marker-assisted selection (MAS), has also been discussed.

/pdf/role-of-drebs-in-regulation-of-abiotic-stress-responses-in-1whj5367cl.pdf

Role of DREBs in regulation of abiotic stress responses in plants

Plants in nature are continuously exposed to several biotic and abiotic stresses. Among these stresses, drought stress is one of the most adverse factors of plant growth and productivity and considered a severe threat for sustainable crop production in the conditions on changing climate. Drought triggers a wide variety of plant responses, ranging from cellular metabolism to changes in growth rates and crop yields. Understanding the biochemical and molecular responses to drought is essential for a holistic perception of plant resistance mechanisms to water-limited conditions. This review describes some aspects of drought induced changes in morphological, physiological and biochemical changes in plants. Drought stress progressively decreases CO2 assimilation rates due to reduced stomatal conductance. It reduces leaf size, stems extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. It disrupts photosynthetic pigments and reduces the gas exchange leading to a reduction in plant growth and productivity. The critical roles of osmolyte accumulation under drought stress conditions have been actively researched to understand the tolerance of plants to dehydration. In addition, drought stress-induced generation of active oxygen species is well recognized at the cellular level and is tightly controlled at both the production and consumption levels, through increased antioxidative systems. This review focuses on the ability and strategies of higher plants to respond and adapt to drought stress.

	 

	Key words: Drought stress, growth, yield, gas exchange, photosynthetic pigments, antioxidative system.

/pdf/morphological-physiological-and-biochemical-responses-of-56gyezzhg3.pdf

Morphological, physiological and biochemical responses of plants to drought stress

Exposure to low temperatures is one of the most important plant abiotic stress factors. In this review we describe the damages that chilling and/or freezing temperatures can cause to plant cells. Confronted to these damages, some plants are able to adapt through mechanisms based on protein synthesis, membrane composition changes, and activation of active oxygen scavenging systems. These adaptive mechanisms rely in part on gene induction. The best understood genetic pathway leading to gene induction upon a temperature downshift is based on C-repeat-binding factors (CBF) activating promoters through the C-repeat (CRT) cis-element. Such activation of transcription factors suggests that cold, as a signal, has been transduced into the cells. Calcium entry is a major signalling event occurring immediately after a temperature downshift. The increase in cytosolic calcium will activate many enzymes, such as phospholipases and calcium dependent-protein kinases. A MAP-kinase module has been shown to be involved in the cold response. Ultimately, the activation of those signalling pathways leads to changes to the transcriptome. In this review we have focused on the genetic and signalling pathways activated early after cold exposure. Much of the data cited is from the model plant Arabidopsis but when possible evidence from other plants is presented.

Cold signalling and cold acclimation in plants

Regulating the drought-responsive element (DRE)-mediated signaling pathway by synergic functions of trans-active and trans-inactive DRE binding factors in Brassica napus.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/j.febslet.2006.01.048

Jing Mei Liu

Papers

Regulating the drought-responsive element (DRE)-mediated signaling pathway by synergic functions of trans-active and trans-inactive DRE binding factors in Brassica napus.

The conserved Ala37 in the ERF/AP2 domain is essential for binding with the DRE element and the GCC box