Leaf Temperature and Vapour Pressure Deficit (VPD) Driving Stomatal Conductance and Biochemical Processes of Leaf Photosynthetic Rate in a Subtropical Evergreen Coniferous Plantation

Yue Li,Jinghua Chen,Shaoqiang Wang,Lei Zhou,Yonggang Chi

doi:10.3390/su10114063

Abstract

Photosynthesis is arguably the most important biochemical process on Earth, which is dramatically influenced by environmental conditions. How environmental factors drive stomatal conductance and biochemical processes of leaf photosynthetic rate has not been sufficiently investigated in subtropical China. In this study, we analysed the effects of stomatal and biochemical parameters on the photosynthetic rate of native Masson’s pine (Pinus massoniana Lamb.) and exotic slash pine (Pinus elliottii Engelm.) in response to leaf temperature and vapour pressure deficit (VPD) in subtropical China, based on leaf gas exchange measurements in 2016. Our results showed that there was no significant difference in the light-saturated photosynthetic rate (Asat) between native Masson’s pine and exotic slash pine. The seasonal patterns of maximum rate of the carboxylation (Vcmax25) were basically consistent with seasonal patterns of Asat for both species. The positive effect of leaf temperature on Asat was mainly produced through its positive effect on Vcmax25. Leaf temperature had no significant effect on stomatal conductance. Vcmax25 and gs simultaneously affected Asat in response to VPD. Our results highlighted the importance of biochemical processes in limiting leaf photosynthetic rate in response to environmental conditions in subtropical evergreen coniferous plantations.

Highlights

Forest ecosystems contain more than 85% of the total plant carbon (C) on Earth [1] and play a major role in the global C cycle
Leaf temperature had no significant effect on stomatal conductance (p > 0.05) (Figure 6a)
This study evaluated the effects of stomatal and biochemical parameters on photosynthetic rate in response to leaf temperature and vapour pressure deficit (VPD) based on leaf gas exchange measurements in subtropical evergreen plantation

Summary

Introduction

Forest ecosystems contain more than 85% of the total plant carbon (C) on Earth [1] and play a major role in the global C cycle. Masson’s pine (Pinus massoniana Lamb.) (MP) is a dominant native species in subtropical China, which covers approximately area of 5.8 million ha [4]. Slash pine (Pinus elliottii Engelm.) (SP), native to the south-eastern United States, covers more than 1 million ha of subtropical China [4,5]. As photosynthesis is arguably the most important biochemical process on Earth and a key source of uncertainty in C cycle modelling [6,7], the direct role of environmental conditions in photosynthetic rate changing had been fully documented [8,9,10]. How the environmental factors drive stomatal conductance and biochemical processes of leaf photosynthetic rate has not been sufficiently investigated in subtropical evergreen coniferous plantations. Studying the internal mechanisms of environmental factors affecting photosynthesis helps us better understand the physiological processes of plants under a changing climate and provides an explanation of the physiological mechanisms for plants growth

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