Análises morfofisiológicas do desenvolvimento radicular e caulinar de cultivares de Vigna unguiculata [L.] Walp. durante estresse hídrico

Abstract

Currently, with climate change and the consequent alterations in the water balances in various regions of the planet, it is becoming increasingly necessary to search for and understand species adapted to these adverse conditions. One of these conditions is the water deficit, where regions such as the Brazilian Northeast, one of the largest dry inhabited areas in the world, is gradually encountering longer periods of drought, damaging and threatening the livelihood of several people. Thus, among the cultivated species, the cowpea is a species of high technological, social, nutritional and ecological interest, in view of its known capacity to tolerate drought and high temperatures. And like other species, Vigna unguiculata [L.] Walp. has several cultivars defined and with their characteristics of interest chosen. Among these cultivars there are individuals considered tolerant to water deficit while others are susceptible. The cowpea is known as a drought tolerant species, however, there are gaps on the relationship of these mechanisms and the morpho-physiological aspects of these cultivars with this tolerance. Thus, the present work aimed to understand the relationship and proportion of biomass produced and allocated in the stem and root portions of the cultivars of cowpea, and its relationship with water deficit. For this, two cultivars of cowpea bean considered tolerant (Pingo-de-Ouro-1,2) and susceptible (Santo Inácio) to water deficit by the literature were selected. In such a way that, at the end of the experiment it was possible to observe that both presented similar performances under the same conditions. It was also possible to report an interesting relationship between the susceptible cultivar and its patterns of root volume, relative water content and water potential. While the parameters of fresh and dry mass and biomass allocation demonstrated a change mainly in the root pattern, probably due to the pattern of secondary root production in the susceptible cultivar, showing a higher relative water content, compared to the cultivar considered tolerant. The parameters of gas exchange reinforce the state of water deficit and a mechanism of stomatal regulation for a more efficient use of water, as well as a possible damage of the photosynthetic apparatus, due to low readings of ETRII and ΔF/Fm', added to a high intracellular concentration of CO2, as well as a low transpiration, photosynthesis and stomatal conductance. Thus, bringing new perspectives in the study of these cultivars and the mechanisms of tolerance to water deficit so characteristic of this plant species.