ABSTRACT
The economically profitable production of crops is related, among other factors, to seed quality, the production system, and the water used in irrigation or preparation of nutrient solutions. Therefore, the objective was to evaluate the phenology, production, and vigor of seeds of mini watermelons grown in saline nutrient solution and different substrates. In the fruit and seed production phase, the experiment occurred in a greenhouse with five electrical conductivities of water for nutrient solution preparation, ECw (0.5, 2.4, 4.0, 5.5, and 6.9 dS m-1), and two growing substrates (coconut fiber and sand). We evaluated the physiological quality of seeds previously produced under the five electrical conductivities of water and two substrates. High salinities for the hydroponic cultivation of the mini watermelon cultivar 'Sugar Baby' accelerated fruit maturation and crop cycle, decreasing fruit size. However, in both substrates, the seed production of mini watermelons, seed viability, and seed vigor occurred adequately with a reject brine of 6.9 dS m-1 in the hydroponic nutrient solution. The seed production of 'Sugar Baby' mini watermelons using reject brine in a hydroponic system with coconut fiber and sand substrates is viable in regions with water limitations.
ABSTRACT
Salvia hispanica seedlings have stood out for their potentialities in nutrients for agri-food industries. Nevertheless, studies related to this species are still scarce, especially with respect to agronomic factors that enable its propagation and development. Hence, this study aimed to evaluate germination, vigor and osmotic adjustment of S. hispanica seeds and seedlings subjected to water and thermal stress. The experimental design was completely randomized, with treatments arranged in factorial scheme, corresponding to five levels of polyethylene glycol (PEG 6000) (0.0; -0.1; -0.2; -0.3 and -0.4 MPa) and five temperatures (20, 25, 30 and 20-30 °C), with four replicates of 50 seeds in each treatment. Germination test was set on blotter paper, moistened with PEG 6000 solutions at the previously mentioned potentials, under 8-h photoperiod. The following variables were analyzed: germination, germination speed index, seedling shoot length, seedling root length, seedling dry matter and contents of chlorophyll, carotenoids, amino acids, proline and sugars. Polyethylene glycol levels of -0.4 MPa at all temperatures and -0.3 MPa at 30 °C and 20-30 °C enable germination and vigor of S. hispanica seedlings. S. hispanica seedlings are able to perform osmotic adjustment under water stress conditions up to the level of -0.3 MPa, when grown from seeds germinated at temperatures of up to 25 ºC.
As sementes de S. hispanica têm se destacado pela sua potencialidade em nutrientes para as indústrias agroalimentares. No entanto, ainda são escassas as pesquisas relacionadas a esta espécie, principalmente no tocante aos fatores agronômicos que viabilizem a sua propagação e desenvolvimento. Com isso, objetivou-se verificar a germinação, vigor e ajustamento osmótico de sementes e plântulas de S. hispanicasubmetidas aos estresses hídrico e térmico. O delineamento experimental foi o inteiramente casualizado, com tratamentos distribuídos em esquema fatorial, correspondente a cinco níveis de polietileno glicol (PEG 6000) (0,0; -0,1; -0,2; -0,3 e -0,4 MPa) e quatro temperaturas (20, 25, 30 e 20-30 °C), com quatro repetições de 50 sementes para cada tratamento. Para isso, instalou-se o teste de germinação em substrato mata-borrão, umedecidos com soluções de PEG 6000 nos potenciais mencionados, sob fotoperíodo de 8 horas de luz. As variáveis analisadas foram germinação, índice de velocidade de germinação, comprimento de parte aérea e das raízes das plântulas, massa seca de plântulas, teores de clorofila e carotenoides, aminoácidos, prolina e açúcares. O nível de polietilenoglicol de -0,4 MPa para todas as temperaturas estudadas, e -0,3 MPa nas temperaturas de 30 °C e 20-30 °C inviabilizam a germinação e o vigor das plântulas de S. hispanica. As plântulas de S. hispanica são capazes de realizar ajuste osmótico sob condições de estresse hídrico até os níveis de -0,3 MPa, quando provenientes de sementes germinadas em temperaturas de até 25 ºC.
