EFFECTS OF WATER RESTRICTION ON CARBOHYDRATES CONCENTRATION, STARCH GRANULES SIZE AND AMYLOLYTIC ACTIVITY IN SEEDS OF PHASEOLUS VULGARIS L. AND P. ACUTIFOLIUS A. GRAY

Background: Seed mass is a key component of adaptation in plants that are strongly affected by development and maturity, and, at the same time, all is modulated by the environment of cultivation. Hypotheses: The response to water deficit in seeds of P. vulgaris L. and P. acutifolius A. Gray is species-dependent and affects their biochemical and morphological characteristics. Studied species: The studied cultivars were Rosa Bufa (P. vulgaris) and cv. 10017 (P. acutifolius). Seeds were obtained from plants grown at 100 % and 25 % soil field capacity during their pod development. Study site and dates: The experiments were performed during May and August 2018 in a greenhouse at the Colegio de Postgraduados, Texcoco, State of Mexico (altitude 2,353 m). Methods: The biochemical and morphological characteristics and the grain size of starch in seeds cotyledons were assessed. Results: Water restriction had no significant effects on the seed thickness, width, or mass only length decreased in P. acutifolius. In both species, the axis size of the starch granules decreased due to the stress, glucose concentration increased, sucrose and starch were not altered. Water imbibition increased six times in P. vulgaris seeds with no effect on the germination. The a-amylase activity was 25 - 35 % lower in both species due to the water restriction, particularly in P. acutifolius the activity was two-fold higher than in P. vulgaris. Conclusions: Comparing the carbohydrate concentration in germinating seeds of common and Tepary beans gave insights on the nutrient reserves mobilization during seed maturation and germination.