A film study of growth activity of hypocotyl in the early phases of the germinating pea seed (Pisum sativum L.)

Abstract

Using the time-lapse cinematography technique, activity of the growing centres of the pea seed hypocotyl (Pisum sativum L.) was followed in the course of the early phases between 15 and 60 hours of germination under standard experimental conditions. The resulting data were plotted in a summary graph with conjugates scales (Fig. 4) indicating time-space limits for further biochemical analysis and the interpretation of mechanism of hypocotyl elongation concerning the dependence of the IAA and RNA content, growth rate, localization of growing zones, transport of substances from the swollen cotyledons into the embryo etc. The most important results are as follows: Between 15 and 20 hours of seed swelling, activity is manifested in two growing centres of the hypocotyl (Fig. 5); between 30 and 36 hours only one zone becomes localized, with a maximum elongation in the region which was originally at a distance of 2·5 mm. from the hypocotyl base. The greatest elongation of the hypocotyl—0·77 mm./hour— was observed between 30 and 48 hours in the zone which was originally at a distance of 2·75 mm. from the hypocotyl base. The zone of maximum growth did not become localized by the termination of the experiment (60 hours) in the presumed zone close to the apex, but was displaced further to the zone which was originally at a distance of 4·0 mm. from the hypocotyl base.