Speed versus endurance tradeoff in plants: Leaves with higher photosynthetic rates show stronger seasonal declines

Yong-Jiang Zhang,Kun-Fang Cao,Xue-Mei Wei,Lawren Sack,Nan Li

doi:10.1038/srep42085

Abstract

We tested for a tradeoff across species between plant maximum photosynthetic rate and the ability to maintain photosynthesis under adverse conditions in the unfavorable season. Such a trade-off would be consistent with the observed trade-off between maximum speed and endurance in athletes and some animals that has been explained by cost-benefit theory. This trend would have importance for the general understanding of leaf design, and would simplify models of annual leaf carbon relations. We tested for such a trade-off using a database analysis across vascular plants and using an experimental approach for 29 cycad species, representing an ancient plant lineage with diversified evergreen leaves. In both tests, a higher photosynthetic rate per mass or per area in the favorable season was associated with a stronger absolute or percent decline in the unfavorable season. We resolved a possible mechanism based on biomechanics and nitrogen allocation; cycads with high leaf toughness (leaf mass per area) and higher investment in leaf construction than in physiological function (C/N ratio) tended to have lower warm season photosynthesis but less depression in the cool season. We propose that this trade-off, consistent with cost-benefit theory, represents a significant physio-phenological constraint on the diversity and seasonal dynamics of photosynthetic rate.

Highlights

We propose that this trade-off, consistent with cost-benefit theory, represents a significant physio-phenological constraint on the diversity and seasonal dynamics of photosynthetic rate
Studies of general leaf design principles or tradeoffs that regulate the seasonal dynamics of photosynthesis have been lacking though they will be fundamental for predicting the response of plants to a future with increased climate extremes
According to a now-classic analysis[9], a trade-off between maximum photosynthetic performance under high resource conditions and the ability to maintain performance under low resource conditions would lead to variation in leaf longevity, such that leaves with higher performance under high resource conditions

Summary

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We tested for a tradeoff across species between plant maximum photosynthetic rate and the ability to maintain photosynthesis under adverse conditions in the unfavorable season Such a trade-off would be consistent with the observed trade-off between maximum speed and endurance in athletes and some animals that has been explained by cost-benefit theory. We resolved a possible mechanism based on biomechanics and nitrogen allocation; cycads with high leaf toughness (leaf mass per area) and higher investment in leaf construction than in physiological function (C/N ratio) tended to have lower warm season photosynthesis but less depression in the cool season We propose that this trade-off, consistent with cost-benefit theory, represents a significant physio-phenological constraint on the diversity and seasonal dynamics of photosynthetic rate. Cycads tend to have long leaf lifespans and a diversity of leaf morphology, structure, and photosynthetic capacity[19,21], and represent an ideal system for testing this leaf design hypothesis

Results and Discussion

Materials and Methods

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