A general non-rectangular hyperbola equation for photosynthetic light response curve of rice at various leaf ages

Junzeng Xu,Linxian Liao,Zhiming Qi,Yuping Lv,Shihong Yang,Qi Wei,Xiaoyin Liu

doi:10.1038/s41598-019-46248-y

Abstract

Photosynthetic light response (PLR) curves of leaves are usually fitted by non-rectangular hyperbola (NRH) equation, and those fitted NRH parameters may change with leaf aging. The objectives of this study were 1) to reveal the response of NRH parameters of rice leaves, light-saturated net photosynthetic rate (Pnmax), quantum yield of assimilation (φ), dark respiration rate (Rd) and convexity of the curve (k), to leaf age; and 2) to improve the performance of NRH equation in simulating the PLR curves for leaves at various ages. The PLR for rice leaves at ages of 3–53 days were measured, and the general NRH equation was developed by incorporating the relationship between NRH parameters and leaf age into the NRH equation. The results showed that the NRH parameters of Pnmax, φ and Rd increased rapidly to maximum at approximately 10 days and then declined linearly toward the age of 53 days. However, the value of k was not sensitive to leaf age. The general NRH equation can be used to simulate leaf PLR continuously along with leaf aging.

Highlights

Leaf photosynthetic light response (PLR) is the fundamental for understanding photosynthetic process driven by photon energy[1,2,3], and for modelling net primary productivity or net ecosystem exchange[4,5]
Leaf nitrogen content and specific leaf mass for herbaceous and woody angiosperms were found highly correlated with PLR parameters, and the interspecific PLR curves were established by linking the PLR parameters of both Mitscherlich and Michaelis–Menten functions to leaf nitrogen content and specific leaf mass[3,14], which were tested to be accurate in depicting PLR curves among species and individual plants
The results indicated that the general non-rectangular hyperbola (NRH) equation performed slightly inferior to the NRH equation

Summary

Introduction

Leaf photosynthetic light response (PLR) is the fundamental for understanding photosynthetic process driven by photon energy[1,2,3], and for modelling net primary productivity or net ecosystem exchange[4,5]. Leaf PLR curves, as well as parameters in the PLR equations, varied greatly among leaves or varieties[14,15,16] Incorporating those influential factors into PLR equations was important for either understanding the plant PLR or modeling plant photosynthesis at different spatial scales[17,18]. SPAD value (a reliable indicator of leaf chlorophyll content)[19,20,21] was incorporated into the NRH equation to build a general PLR equation, which can be used to describe PLR curves of rice leaves with different SPAD values[22] Those researches provide marvelous cases for improving the performance of PLR equation among species, varieties, plants and leaves, which is enlightening for future research. A general NRH equation, capable of simulating PLR curves for leaves at various ages, was constructed by considering the impact of leaf age

Objectives

Methods

Results

Conclusion