Carbon dioxide assimilation and photosynthetic electron transport of tea leaves under nitrogen deficiency.

Qiu-sheng Zhong,Qi-chun Ruan,Xiao-mei You,Zhi-hui Chen,Zheng-he Lin,Chang-song Chen

doi:10.1186/s40529-016-0152-8

Qiu-sheng Zhong, Qi-chun Ruan + Show 4 more

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https://doi.org/10.1186/s40529-016-0152-8

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Abstract

BackgroundTea plant is famed in humid and sub-humid of tropical regions, sub-tropical regions, and is a leaf-harvested crop. Nitrogen is the most important nutrient for increasing quality of tea leaves. Therefore, large amounts of nitrogen fertilizer are increasingly applied by tea farmers. Appropriate application of nitrogen fertilizer aroused people’s concern. This research of physiological response to N deficiency stress will be helpful for appropriate application of nitrogen fertilizer for tea farmers and elucidate a mechanistic basis for the reductions in carbon dioxide (CO2) assimilation.ResultsTo elucidate a mechanistic basis for the reductions in carbon dioxide (CO2) assimilation under nitrogen (N) deficiency tea leaves, changes in chlorophyll (Chl), carbohydrates, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and chlorophyll fluorescence transient were examined together with six N treatment (0, 50, 100, 300, 1200 or 6000 μM N). Root, stem and leaves dry weight (DW) increased as N supply increased from 0 to 300 μM, then remained unchanged. The reductions in CO2 assimilation of N-deficient leaves paralleled with high intercellular CO2 concentration. Rubisco activity, protein and Chl content increased linearly or curvilinearly over the range of leaf N content examined except unchanged as leaf N from 2.15 to 2.79 g m−2. Chlorophyll fluorescence transient from N-deficient leaves displayed a depression at the P-step, accompanied by a new step at about 150 μs (L-step). Fv/Fm, REo/ETo, ETo/ABS, Sm, ETo/CSo, PIabs, PItot, abs, were decreased in N-deficient leaves but increased DIo/CSo, DIo/RC and DIo/ABS. Regressive analysis showed that CO2 assimilation decreased linearly or curvilinearly with decreasing initial rubisco, PIabs and Leaf Chl, respectively. Therefore, we concluded the decreased photosynthetic electron transport capacity, leaf chl content and initial rubisco activity are probably the main factors contributing to decreased CO2 assimilation under N deficiency.ConclusionsThe decreased photosynthetic electron transport capacity, leaf Chl content and initial rubisco activity are probably the main factors contributing to decreased CO2 assimilation under N deficiency.

Highlights

Tea plant is famed in humid and sub-humid of tropical regions, sub-tropical regions, and is a leafharvested crop
Earlier studies in several other crops have indicated that N deficiency reduces ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity (Chen and cheng 2003, 2004), as well as reducing the actual amount of Rubisco produced by the plant
We aimed to determine how N deficiency affects CO2 assimilation, Rubisco, non-structural carbohydrates and photosynthetic electron transport in tea leaves to understand the mechanism by which N deficiency leads to a decrease in CO2 assimilation

Summary

Introduction

Tea plant is famed in humid and sub-humid of tropical regions, sub-tropical regions, and is a leafharvested crop. Lin et al Bot Stud (2016) 57:37 fertilizer to tea plantations have been as high as 450– 1200 kg N ha−1 year−1, which significantly surpasses the recommended rate of 250–375 kg N ha−1 year−1 for high tea yields (Tokuda and Hayatsu 2004; Hirono and Nonaka 2012; Fu et al 2012; Zhu et al 2014) Not surprisingly, such high nitrogen inputs can induce excess residual nitrogen and acidification of soil; both influence the nitrogen cycle of tea fields in which a great deal of nitrogenous gases are produced (Jumadi et al 2008; Zhu et al 2014). N deficiency impacts overall plant metabolism through wide reprogramming of primary and secondary metabolic pathways (Scheible et al 2004)

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