TEGUMENT MECHANICAL CONTROL ON IMMATURE SOYBEAN SEEDS GERMINATION

MONTECHIARINI, N; PERINI, MA; SIN, IN; MARTÍNEZ, GA; CIVELLO, PM; MORANDI, E; GOSPARINI, C

Rosario, Pcia. Santa Fe, Argentina.

Congreso; XVII CONGRESS ? XXXV ANNUAL MEETING ROSARIO BIOLOGY SOCIETY; 2015

Sociedad de Biología de Rosario

Developing soybean seeds (Glycinemax (L.) Merr.) do not exhibit viviparity, although they can be induced togerminate on adequate in vitro conditions afterhistological differentiation is completed, i.e., nearly 21 days after anthesis(DAA). However, germination rates arelower than in dry mature seeds, thus indicating the existence of germination restrictions.The main control is the embryo axis ABA level.Moreover, from 25 DAA, both embryos (seeds without tegument) and isolatedembryo axis (neither tegument nor cotyledons) have similar germination rates which are higher than in whole seeds. This shows ategument restriction on precocious germination. The tegument could be a physical barrier on the mycropilar area where the embryoaxis protrusion occurs. The objective of this work was to measure the tegument resistance on the mycropilar area, and to determine thetegument resistance evolution during seed development.One hundred teguments per age were evaluated, on 25, 30, 35, 40 and 45 DAA. Theresistance was measured using a TA XT Plus Texture Analyzer. The results were analyzed by ANAVA and LSD test (p<0.05).The pressure needed to protrude the tegument increasedthrough the seed development: there were no differences between 25 and 30 DAA(1.27 and 1.30 MPa, respectively) nor between 40 and 45 DAA (1.62 and 1.63 MPa, respectively), but 35 DAA (1.38 MPa) wassignificantly different from both. From 25 to 45 DAA, with ahigh water content (≥58%), the mechanical resistance of tegument on themycropilar area was increased, while the embryo axis ABA level dropped. These results support the hypothesis that, before the beginningof the rapid seed dehydration, the mechanical resistance of tegument to the radicular protrusion would contribute to the control ofprecocious germination by avoiding the viviparity, still when the embryo axis ABA level is lower than the inhibition threshold.