The application of sanitary sewage using subsurface drip irrigation contributes to mitigating the current problems of water availability and food production. The aim in this study was to evaluate cowpea receiving sanitary sewage through drippers operating at different flow rates and depths. The drippers operated at flow rates of 1.6 and 3.8 L h(-1) and were installed at depths of 0, 5, 10, 15, 20, 25, and 30 cm. Cowpea was grown in 65 L pots filled with sandy clay soil in a greenhouse. Synthetic sanitary sewage was used and the amount applied to the pots was based on the limiting element, which in this case was nitrogen, for growing cowpea. Irrigation was managed using TDR probes. Germination and the physiological responses and morphology of cowpea roots were assessed. Capillary rise, when water was applied in subsurface, was not sufficient to evenly moisten the soil surface. The germination variables decreased as a result of the increase in drip installation depths. The distribution of water as the depth of the emitters increased was responsible for the damage to the physiological and morphological responses of cowpea roots. The flow rates of the drippers did not affect the germination of cowpea. Using the subsurface drip irrigation system was not appropriate for growing cowpea under the conditions of this study.

Plants exposed to adverse environmental conditions develop molecular mechanisms of adaptation and/or defense, the osmoprotectors, which function as compatible solutes and contribute to tolerance via prevention systems and protection against cellular damage caused by these abiotic stresses. This study aimed to identify and characterize the osmoprotectors proline and trehalose in cowpea plants cv. Carijo under controlled conditions of water-deficit and heat stress based on the IPCC scenario of 4.8 degrees C increase in temperature, evaluating their structure and function through computational methods, as well as gene expression by RT-qPCR. The experimental assays were carried out in growth chambers under controlled conditions with different levels of soil water availability, phenological phases and temperature regimes. From the in silico analyses, ten TPS genes and one P5CR gene were identified in Vigna unguiculata, and these were named according to their chromosomal location. The VuP5CR and VuTPS genes play roles in hormone pathway signaling and in the response to light and biotic and abiotic stresses. The genes P5CR (proline) and alpha TPS6 (trehalose) were induced with increased temperature and lower water availability in the vegetative phase of cowpeas. In addition, P5CR also showed induction with 50% water availability at high temperatures. In the pod filling phase, the P5CR and alpha TPS6 genes were repressed with water availability of 75%, while only the P5CR gene was induced when water availability was reduced to 25% under heat stress. P5CR and TPS6 genes were induced in cowpea cv. Carijo in response to associated abiotic stresses (water-deficit and high temperatures), which suggests their participation in the mechanisms of adaptation of the species in adverse environmental conditions.