Aspectos fenológicos e qualidade fisiológica de sementes de Moringa oleifera Lam

Abstract

Phenology describes repetitive biological events, making it possible to relate these events to biotic and abiotic factors. And for seed germination, the tetrazolium test would be a promising alternative, as it is a quick test that provides a detailed analysis of viability and vigor. On the other hand, Moringa oleifera Lam. is a species that has multiple uses, being widely distributed in tropical countries. With this, the objectives of the present work were to study the phenological behavior of M. oleifera and to relate the variations in the phenophases with the climatic factor’s precipitation and temperature and beside to determine the efficiency of the tetrazolium test for evaluation of the physiological quality of seeds, concomitantly to the its optimization. The experiment was carried out at the Laboratory of Pyrotechnics of the Campus of Engineering and Agricultural Sciences - UFAL, using six lots of M. oleifera seeds from the experimental area of CECA, harvested in the 2020 and 2021 harvests. To record the phenological data, ten trees were selected, with the records being made between the first half of August 2020 and the first half of July 2021, recording the presence and absence of the flowering and fruiting phenophases, determining the Fournier intensity index. These intensity data were related to the fortnightly average precipitation and temperature through Spearman's correlation. For the tetrazolium test, the seeds were first preconditioned to facilitate cutting, and only the cotyledons containing the embryo were immersed in the tetrazolium solution, at a concentration of 0.05%, for a 3-hour staining period in a Biochemical Oxygen Demand chamber at 30 oC in the dark. Seeds whose embryonic axis was pink were classified as viable, and seeds whose embryo was yellow, very intense red or discolored were classified as non-viable. To separate different categories of seeds, they were evaluated one by one regarding the condition of the tissues and their color, and the position and size of the damage observed in the cotyledons, plumule and hypocotyl-radicle axis. The evaluation was carried out under a magnifying glass of six magnifications (6X) with fluorescent lighting, and disposed on a table scanner glass and digitized, with images stored in a JPG file. M. oleifera phenophases intensified in August, September and December 2020, showing Fournier intensity peaks of 47.5 and 77.5, 72.5 and 92.5, and 35 and 55%, respectively, and April and June 2021, in the monthly intervals of greater rainfall, with percentage rates of 82.5 and 95, 77.5 and 80%, respectively. Batches no 4 (April/2021) and 5 (June/2021) showed viability of 96 and 97%, and very high vigor, 91 and 92%, respectively, not presenting serious problems related to any damage. The intensity and duration of flowering and fruiting phenophases in M. oleifera are synchronized with the temporal distribution of precipitation pulses in that habitat. The viability of M. oleifera seeds can be evaluated using a concentration of 0.05% tetrazolium at 30 oC for three hours of immersion in salt.