Abstract
Water is one of the most compromising factors in the germination and initial growth of seedlings, where its restriction causes a reduction in the water potential of cells in addition to causing oxidative stress. Ascorbic acid (AsA) is known to protect organelles and cells against the accumulation of ROS. The aim of this work was to study the effects of ascorbic acid on the conditioning of cowpea seeds subjected to water stress. The seeds of the BRS Marataoa and Setentao genotypes were conditioned at a concentration of 0.0 (control), 0.25, 0.50, 0.75 and 1.00 mM AsA, and sown on paper rolls (Germitest®) moistened with mannitol solution at a potential of 0.0 (control), -0.3, -0.6, -0.9 and -1.2 MPa, and stored in a germination chamber (BOD) at 25 oC. The experiment was conducted in a completely randomised design, in a 2×5×5 factorial scheme, with four replications of 50 seeds per treatment. The variables under analysis were percentage germination, first germination count, germination speed index, shoot and root length, total seedling dry weight and electrolyte leakage in the leaves and roots. Conditioning the seeds with ascorbic acid at a concentration of 0.50 mM for the BRS Marataoa genotype and 0.75 mM for the Setentao genotype, enabled the development of more vigorous seedlings and a reduction in the damage caused to the membranes by oxidative stress, both in the absence of a water deficit and at the osmotic potentials under test, including at the lowest potential.
Highlights
Water is one of the most compromising factors in the germination and initial growth of seedlings, as it makes up the matrix necessary for most biochemical and physiological processes (TAIZ et al, 2017)
Tissues are hydrated and respiration is intensified (CARVALHO; NAKAGAWA, 2012; MARCOS FILHO, 2015), and control is maintained over the structure and property of proteins, membranes, nucleic acids and other cellular constituents (TAIZ et al, 2017)
The seeds showed different values for the degree of moisture and thousand-seed weight, where 13% and 182.5 g was found for the BRS Marataoã genotype, and 11% and 178.3 g for the Setentão genotype respectively
Summary
Water is one of the most compromising factors in the germination and initial growth of seedlings, as it makes up the matrix necessary for most biochemical and physiological processes (TAIZ et al, 2017). Water restrictions in the soil, a common phenomenon in arid and semi-arid regions, cause a reduction in the water potential of plants and, in turgor, increasing ionic toxicity and inhibiting photosynthesis, leading to a limitation on the physiological and biochemical functions of the cells. Faced with these conditions, plants activate complex mechanisms of response to water scarcity, involving detrimental and/or adaptive changes, to avoid or tolerate the period of stress (LISAR et al, 2012). The generation and elimination of ROS is in a state of dynamic equilibrium, but when under stress, there is an imbalance in this relationship, which results in the accumulation of ROS (KRANNER et al, 2010)
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