INTEGRAÇÕES MORFO-FISIOLÓGICAS DE RAIZ E PARTE AÉREA CONFEREM TOLERÂNCIA À SECA EM PLANTAS DE Crambe abyssinica Hochst e Raphanus sativus L.

Abstract

Precocity, rusticity, good productivity and high oil content are attributes that enable the cultivation of Raphanus sativus and Crambe abyssinica during the off-season in the Central regions of Brazil. The water deficit occurrence, however, may be limiting these crops cultivation, since the planting season coincides with the dry season in the region. The literature information scarcity about the ecophysiology of these species exposed to stress conditions turn essential to carry out studies in this direction. Thus, the objective was to evaluate the water deficit effects on shoot and root system characteristics of Crambe abyssinica and Raphanus sativus as well as to identify which of these characteristics are related to drought tolerance of these species. In study I, plants of Raphanus sativus L. were cultivated in field under treatments composed by 100% (control), 66% and 33% of field capacity (water deficit), in the phenological development stages of vegetative, flowering and grain filling. The experimental was a randomized block design in a split plot scheme, with four replicates. Physiological, biochemical traits, production components and physicochemical quality of crude oil extracted from seeds were evaluated. Results demonstrated the Raphanus sativus physiological tolerance to water deficit during the vegetative growth stage and sensitivity during the grain filling stage. In study II, Crambe abyssinica and Raphanus sativus were cultivated in citrus plants in a greenhouse under full irrigation conditions (control, 90% of field capacity), water deficit (WD, 40% of field capacity), 7, 14 and 21 days, and rehydration (RT), to evaluate the plants' recovery capacity after 48 hours of irrigation restoration. Experimental design was randomized blocks, with five replications. After each period of water deficit and rehydration imposition, the water relations, gas exchange, chlorophyll a fluorescence, chloroplast pigment content, electrolyte release rate, malondialdehyde content, antioxidant enzyme activity, leaf micromorphometry and morphological traits of the shoot and root system were evaluated. Results indicated higher sensitivity of Crambe abyssinica and Raphanus sativus to water deficit lasting 14 and 21 days, however, with activation of adaptive mechanisms of the shoot and root system. Stress tolerance responses evolved maintenance of cell turgor, increased activity of antioxidant enzymes and smaller root diameter. Raphanus sativus demonstrated higher tolerance to water deficit and rapid plant recovery, mainly due to the root system efficiency.