Chilling injury in germinating seeds: basic mechanisms and agricultural implications

Abstract

AbstractGerminating seeds of many species, especially those of tropical or subtropical origin, suffer chilling injury when exposed to low but non-freezing temperatures, resulting in poor seedling establishment and reduction in yield. The severity of injury depends upon several factors such as (i) the species or the cultivars involved, (ii) the initial water content of the seed, (iii) the temperature to which seed is exposed, (iv) the duration of chilling exposure and (v) the period during the course of germination when the chilling exposure takes place. The period of imbibition by seeds is the period of sensitivity to the stresses but especially to chilling temperatures. Imbibitional chilling injury is defined as sensitivity to a combination of low seed-water content and imbibition at cold temperature. The mechanism of chilling injury in seeds is different from chilling injury of hydrated tissues and is discussed in relation to the involvement of membranes, respiration, rate of hydration and the concept of discreet moisture levels. Furthermore, the mechanistic and applied aspects of pre-sowing seed treatments for improved germination performance under chilling stress are discussed with an emphasis on hydration-dehydration, osmotic priming and growth regulator treatments.