Dehydration tolerance (DhT, also “dehydration tolerant”) is an important functional trait enabling plants to occupy habitats with fluctuating water availability. This trait is rare in vascular plants, but relatively common among cryptograms and may be one way in which these small organisms are able colonize marginal habitats and avoid competition with larger plants. DhT has been well studied, and consequently we have learned a great deal about how plants survive dehydration events, but less is know on the consequences of being DT. One such consequence of being DhT could be trade offs with other traits related to survival, growth, and reproduction. How DhT trades off with reproductive investment is particularly relevant as it has significant implications on plant productivity and species persistence in face of a changing climate.
Taking an integrative approach, we tested the hypothesis that DhT and reproductive investment trade off. We addressed this question by drawing on aspects of ecology, physiology, and genomics. In three laboratory studies we tested, 1) the effect of dehydration on sexual reproduction, 2) the consequences of reproduction on DhT using plants cultured in a common garden, and 3) sex specific differences in DhT. We further investigated the putative trade off between DhT and reproductive investment at a genomic level. First, we conducted a transcriptomic study to assess the changes in DhT gene expression across reproductive stages. Second, we investigated sex specific genomic coverage of DhT genes, which we correlated to sex specific differences in reproductive investment.
Results/Conclusions
We found that dehydration significantly delays reproduction, and that the delay is proportional to the intensity of the dehydration event. We also found that, contrary to our initial prediction, sex structures are more DhT than vegetative structures, but that specific DhT genes were down regulated in the sexual structures. Taken together this suggests that the mechanism of DhT is tissue specific, but does not imply a simple trade off between these two traits. Additionally, we detected a significant sex difference in DhT. Females showed higher DhT than males and females also had higher coverage of DhT associated genes in their genome. Males had lower DhT, but are more precocious (invest in reproduction sooner than females). This suggests that DhT and reproductive investment may inherently trade off, or that the sexes have been under contrasting selection for these two traits.