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

Water deficit and salinity, especially under high light intensity or in combination with other stresses, disrupt photosynthesis and increase photorespiration, altering the normal homeostasis of cells and cause an increased production of reactive oxygen species (ROS). ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules. In this review, we provide an overview of ROS homeostasis and signalling in response to drought and salt stresses and discuss the current understanding of ROS involvement in stress sensing, stress signalling and regulation of acclimation responses.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2009.02041.x

Reactive oxygen species homeostasis and signalling during drought and salinity stresses

LEARNING The objectives of BIOS 781 are to present: OBJECTIVES: 1. basic population and quantitative genetic principles, including classical genetics, chromosomal theory of inheritance, and meiotic recombination 2. an exposure to QTL mapping methods of complex quantitative traits and linkage methods to detect co-segregation with disease 3. methods for assessing marker-disease linkage disequilibrium, including case-control approaches 4. methods for genome-wide association and stratification control.

Genetic Data Analysis

Plant responses to different stresses are highly complex and involve changes at the transcriptome, cellular, and physiological levels. Recent evidence shows that plants respond to multiple stresses differently from how they do to individual stresses, activating a specific programme of gene expression relating to the exact environmental conditions encountered. Rather than being additive, the presence of an abiotic stress can have the effect of reducing or enhancing susceptibility to a biotic pest or pathogen, and vice versa. This interaction between biotic and abiotic stresses is orchestrated by hormone signalling pathways that may induce or antagonize one another, in particular that of abscisic acid. Specificity in multiple stress responses is further controlled by a range of molecular mechanisms that act together in a complex regulatory network. Transcription factors, kinase cascades, and reactive oxygen species are key components of this cross-talk, as are heat shock factors and small RNAs. This review aims to characterize the interaction between biotic and abiotic stress responses at a molecular level, focusing on regulatory mechanisms important to both pathways. Identifying master regulators that connect both biotic and abiotic stress response pathways is fundamental in providing opportunities for developing broad-spectrum stress-tolerant crop plants.

The interaction of plant biotic and abiotic stresses: from genes to the field

Salinity is a major abiotic stress limiting growth and productivity of plants in many areas of the world due to increasing use of poor quality of water for irrigation and soil salinization. Plant adaptation or tolerance to salinity stress involves complex physiological traits, metabolic pathways, and molecular or gene networks. A comprehensive understanding on how plants respond to salinity stress at different levels and an integrated approach of combining molecular tools with physiological and biochemical techniques are imperative for the development of salt-tolerant varieties of plants in salt-affected areas. Recent research has identified various adaptive responses to salinity stress at molecular, cellular, metabolic, and physiological levels, although mechanisms underlying salinity tolerance are far from being completely understood. This paper provides a comprehensive review of major research advances on biochemical, physiological, and molecular mechanisms regulating plant adaptation and tolerance to salinity stress.

/pdf/mechanism-of-salinity-tolerance-in-plants-physiological-3ixvqhezre.pdf

Mechanism of Salinity Tolerance in Plants: Physiological, Biochemical, and Molecular Characterization

In the present investigation, three different triazole compounds triadimefon (TDM), paclobutrazol (PBZ) and propiconazole (PCZ) were used to study their effects on the leaf anatomical characteristics of Amorphophallus campanulatus. The triazole treated leaves showed several variations in leaf thickness, number of stomata, stomatal pore length, width of stomata, number of spongy cells, palisade cells and number of chloroplast per palisade and spongy cells when compared to the leaves of the untreated control plants. From the results of this experiment, it can be concluded that, the triazoles appeared to show an impact on anatomical characteristics of A. campanulatus.

Leaf anatomical responses of Amorphophallus campanulatus to triazoles fungicides

A pot culture experiment was conducted to estimate the effect of cobalt (0, 50, 100, 150, 200 and 250 mg kg-1soil) on morphological parameters, drymatter production, yield and yield components of soybean. Pot culture experiments were conducted during January 2006 to April 2006. Periodical observations were made to record the various morphological parameters, dry matter production and yield responses of soybean. From the results, it is observed that, cobalt at lower concentrations have some beneficial values on soybean.

/pdf/effect-of-different-concentrations-of-cobalt-on-iha0fxyjzp.pdf

Effect of Different Concentrations of Cobalt on Morphological Parameters and Yield Components of Soybean

A glimpse of lignicolous marine fungi occurring in coastal water bodies of Tamil Nadu (India).

Effect of physical desiccation on plant regeneration efficiency in rice (Oryza sativa L.) variety super basmati.

6 Abstract: The present study was conducted to find out the antibiogram of different extracts of two varieties of Catharanthus roseus (L.) G. Don. "rosea" and "alba". The plant parts, leaves, stems, roots and flowers were separately tested for their antibiogram by using different solvents (methanol, acetone and ethyl acetate). Among the three solvents used for antibiogram, ethyl acetate extracts of different plant parts were found to induce best antibiogram followed by methanol and acetone extracts. Of the two varieties tested, "rosea" had better antibiogram than "alba". Extracts of all parts of both varieties of C. roseus like root, stem, leaf and flower were found to cause the largest antibiogram towards Bacillus subtilis followed by Klebsiella sp. while least antibiogram was observed against Streptococcus sp. The Staphylococcus aureus was moderately sensitive to different solvent extracts of the plant. The best antibiogram of ethyl acetate could be attributed to hig h solubility of the active compounds of Catharanthus in this solvent compared to other solvents.

/pdf/antibiogram-of-catharanthus-roseus-extracts-5o3jal3gs8.pdf

Cheruth Abdul Jaleel

Papers

Leaf anatomical responses of Amorphophallus campanulatus to triazoles fungicides

Effect of Different Concentrations of Cobalt on Morphological Parameters and Yield Components of Soybean

A glimpse of lignicolous marine fungi occurring in coastal water bodies of Tamil Nadu (India).

Effect of physical desiccation on plant regeneration efficiency in rice (Oryza sativa L.) variety super basmati.

Antibiogram of Catharanthus roseus Extracts