Plant growth and production are severely affected by various biotic and abiotic stress factors. Drought is one of the major abiotic stress which badly affects crop growth and yield. It reduces the photosynthetic ability and crop production rate of plants and induces changes of chlorophyll content.
Legumes are important agricultural food crops which are cultivated in every climatic region on a worldwide range of all the soil types. Legumes are only second to cereals in terms of contribution to food security. Drought stress adversely affects legume production which is the largest producers of pulses i.e. 70% of global production occurred in regions of the world that facing drought stress.
Salicylic acid is a powerful signalling molecule in plants which display specific responses to biotic and abiotic stresses. It modulates plant responses to drought stress and induces multiple stress tolerance in plants. It plays a very important role due to its ability to induce a protective effect on plants against drought stress. It induces systemic acquired resistance SAR in plants against different pathogens which are manifested in the appearance of pathogenesis-related proteins.
Ascorbic acid is an antioxidant molecule which completes the essential metabolic reactions in the life of plants. It serves as a co-factor for many enzymes and it causes the detoxification of reactive oxygen species. AA is used for cell growth, cell division, cell cycle and many other mechanisms of plant and as a co-factor for many enzymes.
Ascorbic acid and salicylic acid both affect the metabolism of plant reactions and cause many changes in them. These changes are sometimes accounted as adaptabilities which increase the resistance of plants against the environmental factors i.e. drought stress tolerance. This study intends to investigate the growth performance of pea plant by use of different concentrations of salicylic acid and ascorbic acid against drought stress and to evaluate the different physiological and biochemical parameters of the plant by foliar application of these compounds.
Drought stress affects the different stages of photosynthesis and proteins of the chloroplast, lipids peroxidation, proteins metabolism and the plant's growth regulators i.e. phytohormones. It causes the reduction and decomposition of chlorophyll. Due to its harmful effects, the ability of opening pores (stomata) is reduced, and during intense conditions of drought stress, the pores do not support to the external factors and remain close.
Pea (Pisum sativum .L) is the most important leguminous vegetable of the winter season and its pods consist of a large quantity of protein and carbohydrates. So, it is remarked as a big source of proteins for nutrition all over the world. Its seed contains 18-20% dry matter from which 10-12% is carbohydrate and 5-8% is protein. Pea is used as a fresh vegetable and canned. About 12.2 million tons of pea mass production is attained in 6.3 million ha farming all over the world.
The experiment was conducted to check the growth performance of Sarsabz variety pea (Pisum sativum L.) plant under drought stress with the application of different concentration of salicylic acid and ascorbic acid. The experiment was conducted in complete randomized design (CRD) in five groups where each block consisted of six replicates for further treatment. Six pots were kept as control (without drought stress) and six pots were kept as a negative control with drought stress. Three groups of pots (1,2,3) were treated at a time with the different concentration of salicylic acid and ascorbic acid i.e. 0.5 mM, 1.0 mM and 1.5 mM respectively.
The pot-grown-plants were harvested after forty-five days of SA and AA treatment and various morphological parameters were studied. Results showed that there was a notable decrease in many growth parameters due to drought stress in pea plant, but all these parameters were increased by the application of different concentrations of SA and AA. Due to drought stress values of some parameters were decreased and by the application of SA and AA at different concentrations these parameters were increased i.e. plant height, root and shoot length, number of branches per plant, number of leaves per plant, leaf area, fresh and dry weight per plant, number of pods per plant and number of seeds per pod, relative water content, chlorophyll a, b contents etc.
But values of some parameters were increased during drought stress and reduced by the application of SA and AA at different concentrations i.e. Malondialdehyde content (MDA), membrane permeability, anthocyanin, hydrogen peroxide (H2O2) etc. Drought stress caused the reduction of pea plant performance but the combined application of SA and AA at different concentrations reduced the effect of drought stress and improved all the parameters affected by drought stress to enhance the crop growth and yield.