Dormancy and germination responses of kiwifruit (Actinidia deliciosa) seeds to environmental cues

Abstract

Seed germination of the kiwifruit (Actinidia deliciosaA. Chev. C.F. Liang and A.R. Ferguson), a deciduous, perennial vine, is low because of seed dormancy. The main purpose of this study was to characterize kiwifruit seed dormancy and germination in response to environmental factors such as temperature and light. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification) of at least 3 weeks at 2 or 5°C. Alleviation of dormancy is accomplished by incubation at fluctuating temperatures (20/30°C). A red light pulse did not affect germination, whereas a far-red light pulse strongly inhibited germination. This inhibition was readily reverted by a second pulse of red light, indicating that phytochromes are also involved in dormancy alleviation. Although seed germination was inhibited by the fruit pulp, the latter prevented neither perception of low temperature nor changes in the light sensitivity of the seeds. Therefore, it can be advanced that kiwifruit seeds will only germinate after dispersal if the time–temperature requirement for dormancy alleviation and fluctuating temperatures for dormancy termination are fulfilled. Perception of a closed canopy might interfere with dormancy termination.

Optimizing Seed Germination and Seedling Growth in Different Kiwifruit Genotypes

“…It seems that temperature and light treatments increased seed germination percentage when stratification was complete, which was consistent with the results from Windauer et al [10]. The results also confirmed the positive effect of stratification period on seed germination percentage in different genotypes.…”

“…In kiwifruit, however, red light does not affect seed germination, but far-red light, even for a short period of time, can strongly inhibit germination. In addition, incubation of stratified seeds at fluctuating temperatures compared to constant ambient temperature significantly increases the germination percentage [10]. Temperature and plant phytochromes are factors that can play an effective role in seed dormancy.…”

“…They also found a positive effect of fluctuating temperature (20/30) on breaking kiwifruit seed dormancy. However, red light had no role in kiwifruit seed germination, but far-red light had an inhibitory role in germination [10].…”

“…Seed dormancy is a physiological condition that reduces or inhibits germination in favorable conditions. Previous studies suggested low temperature and gibberellic acid can overcome kiwifruit seed dormancy [8][9][10][11]. Kiwifruit seed dormancy is a physiological condition that restricts or prevents germination in otherwise favorable conditions and determines the range of conditions permissive for germination.…”

“…Additionally, germination is a complex process that cannot be fully understood by studying one or two factors; thus, it is necessary to adopt a multidimensional strategy, combining the analysis of multiple factors to achieve optimal germination percentages. The intrinsic molecular mechanisms determining dormancy can have an embryo and/or a coat component that can interact to determine the degree of 'whole-seed' dormancy [8,10].…”