Compound and simple leaf woody species of the Chilean matorral are equally affected by extreme drought

Abstract

Two main leaf types are recognized among vascular plant species: compound and simple. Compound leaves are believed to be photosynthetically more productive than simple ones, by diluting mass tissue in more projected area. Conversely, simple leaves are believed to be more stress tolerant by packing mass tissue in less projected area during stress like drought. Nevertheless, convective cooling is more e cient in compound than simple leaves, a process that could alleviate water loss in drought periods. In Central Chile, woody species with simple and compound leaves coexist. This zone is facing a mega-drought event, causing browning and tree mortality. However, photosynthetic limitations on both types of leaves in drought conditions have not been addressed so far. We measured photosynthetic limitations in wellwatered and drought conditions in three compound and three simple leaf species, and drought response ratio were obtained. We hypothesized that with no water limitation compound leaf species will show higher net photosynthesis (A N ) than simple leaf species associated with a higher mesophyll conductance (g m ). Nevertheless, opposite results are expected for simple leaves because their stress-tolerant physiology, showing fewer changes in their photosynthetic traits. We found that (g m ) and (A N ) were larger in compound leaves in well-watered conditions. Under drought conditions, both types of leaves were negatively affected despite foliar temperature in compound leaf species was 4°C lower. Our result suggests that regardless leaf shape matorral species in Central Chile will be seriously affected in their A N due to the megadrought currently affecting this zone.

Impacts of the Major Drought in Chile and Mitigation Measures

“…In Chile, many plants are suffering from devastating effects of the megadrought. For example, grass is becoming a rare luxury, pollination is badly affected and disrupted, and the "browning" of vegetation is common and irreversible [9,10].…”