The effects of constan temperatures, light and seed quality on the germination characteristics of Agave americana

Abstract

The influence of constant temperatures, light and seed quality on A. americana seed germination was investigated with the objective of detailing the environmental control for germination in this species. The lower and upper temperature limits for germination (radicle emergence) and seedling production in the light (12 h d-1) were between 11°C and 16ºC, and 36°C and 40ºC, respectively. Maxima for both these growth parameters were evident at temperatures between 21 ºC and 31 ºC, and the minimum mean time for germination (MTG) occurred at 26ºC. Reducing photoperiod to ca. 1 min white light per day («nominal dark» treatment) did not significantly affect the level of germination (radicle emergence) or seedling production, but MTG was significantly increased. Incubation in «complete darkness» ( green light used for scoring) resulted in lower germination and seedling production at 26°C compared to both nominal darkness and light conditions, and MTG was increased in comparison to the light treatment. MTG at 26°C was progressively increased with lowered seed quality induced by accelerated aging under seven environmental conditions; a negative linear relationship was observed between the probit percent of germination and log-MTG. The results indicate that temperature, light and seed quality influence the germination response in A. americana.