Climate change compromises leaf units and lignin content in sun-tolerant Paubrasilia echinata plants

Abstract

It is of great global interest how shade-tolerant and sun-tolerant species will respond to the Representative Concentration Pathways (RCP) scenarios of climate change predicted by the end of the 21^st century. To elucidate this question, we used young plants of the shade- and sun-tolerant ecotypes of Paubrasilia echinata, a tree native to the Brazilian Atlantic Forest. Plants were grown in three climate scenario simulations: current Atlantic Forest for the southeast region of Brazil (CAF); average temperature of CAF + 2.0 ºC and 580 ppm CO₂ (RCP 4.5); and average temperature of CAF + 3.5 °C and 936 ppm CO₂ (RCP 8.5). Two substrate moisture conditions were established for each scenario: 40 (water deficit) and 80% (control). After 90 days of cultivation in these microclimatic conditions, we carried out growth analyses (survival, number of folioles and foliolules of their compound leaves and increase in stem elongation), non-structural carbohydrate content (sugars and starch) and cell wall polymer content (cellulose, hemicelluloses and lignin). The pessimistic climate scenario (RCP 8.5 + water deficit) inhibited photosynthesizing leaf area production (number of folioles/foliolules) of the shade-tolerant ecotype more, but without affecting survival. In this climate scenario, the shade-tolerant ecotype showed a greater capacity to accumulate sugars than the other ecotype. Also in the pessimistic climate scenario, the shade-tolerant ecotype accumulated more of this polysaccharide in the stem, while in the sun-tolerant ecotype this occurred in the root. This scenario increased the cellulose content of both ecotypes to the detriment of the lignin content of the sun-tolerant ecotype. We conclude that the rise in CO₂, temperature and DPV along with low precipitation in RCP 8.5 predicted for the southeastern region of Brazil by the end of this century may compromise more the photosynthesizing leaf area production of the shade-tolerant ecotype and the wood quality of the sun-tolerant ecotype of P. echinata. However, this does not threat their survival.