Functional traits and trait coordination change over the life of a leaf in a tropical fern species

Abstract

Premise Plant ecological strategies are often defined by the integration of underlying traits related to resource acquisition, allocation, and growth. Correlations between key traits across diverse plants suggest that variation in plant ecological strategies is largely driven by a fast–slow continuum of plant economics. However, trait correlations may not be constant through the life of a leaf, and it is still poorly understood how trait function varies over time in long‐lived leaves. Methods Here, we compared trait correlations related to resource acquisition and allocation across three different mature frond age cohorts in a tropical fern species, Saccoloma inaequale. Results Fronds exhibited high initial investments of nitrogen and carbon, but with declining return in photosynthetic capacity after the first year. In the youngest fronds, we found water‐use efficiency to be significantly lower than in the oldest mature fronds due to increased transpiration rates. Our data suggest that middle‐aged fronds are more efficient relative to younger, less water‐use efficient fronds and that older fronds exhibit greater nitrogen investments without higher photosynthetic return. In addition, several trait correlations expected under the leaf economics spectrum (LES) do not hold within this species, and some trait correlations only appear in fronds of a specific developmental age. Conclusions These findings contextualize the relationship between traits and leaf developmental age with those predicted to underlie plant ecological strategy and the LES and are among the first pieces of evidence for when relative physiological trait efficiency is maximized in a tropical fern species.

Reproductive phases coincide with changes in morphology and photosynthetic physiology in an endangered cycad species

“…Further research is required to quantify the timing of acquisition, translocation and allocation of carbon that is used for reproduction and leaf development so that conservation practitioners could best promote leaf growth and reproduction in this species. For example, future research could make similar measurements to those reported here over longer timescales to account for physiological differences between leaves of different developmental ages ( Krieg et al, 2023 ), while individual plants alternate between fertile and sterile reproductive states over time.…”