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How Warming Impacts the Germination and Vigor of Plants Grown from Recalcitrant Seeds
Sershen, Perumal, A., Varghese, B., Govender, P., Ramdhani, S. and Berjak, P. 2014. Effects of elevated temperatures on germination and subsequent seedling vigor in recalcitrant Trichilia emetica seeds. South African Journal of Botany 90: 153-162.

The authors write that "our knowledge of the effects of elevated temperatures on seeds and seedlings is almost exclusively based on species that produce orthodox (i.e., desiccation tolerant) seeds," as per Baskin and Baskin (1998) and references therein; and they say "this is alarming since an increasing number of African species are being shown to produce recalcitrant seeds," citing Berjak and Pammenter (2008). And why is this alarming? It is alarming, according to Sershen et al., because "recalcitrant, unlike orthodox seeds have to germinate shortly after shedding (or else die) and do not remain dormant within natural seed banks," as also described by Berjak and Pammenter (2008).

What was done
To further explore this subject, according to the six South African scientists, freshly harvested Trichilia emetica seeds (which are recalcitrant) were grown at ambient day/night temperatures of 24/14°C and elevated midday/night temperatures of 29/20°C, while they were monitored for degree of germination, respiratory activity, reactive oxygen species production, total antioxidant activity and their ultrastructural integrity, after which the seedlings produced from them were subjected to various physical and chemical analyses, along with growth measurements, in order to compare the relative vigor of those that developed in the ambient and elevated temperature treatments.

What was learned
Sershen et al. determined that exposure to the elevated temperatures of their study did not disrupt the metabolic and ultrastructural integrity of T. emetica's embryonic axes, and that it thus did not compromise seed germination and subsequent seedling production. In fact, they found that the extra warmth provided to the seeds actually enhanced their germination velocity.

What it means
As for what the researchers' several findings imply about the future, they say they suggest that "elevated temperatures may improve the ability of T. emetica to compete with neighboring species during the seedling establishment phase, by enhancing seedling growth rates, leaf area, and biomass allocation to aerial parts of the plants," all of which phenomena are very important, especially to a tree seedling in the midst of a tropical forest!

Baskin, C.C. and Baskin, J.M. 1988. Germination ecophysiology of herbaceous plant species in a temperate region. American Journal of Botany 75: 286-305.

Berjak, P. and Pammenter, N.W. 2008. From Avicennia to Zizania: seed recalcitrance in perspective. Annals of Botany 101: 213-228.

Reviewed 14 May 2014