Effects of nitrogen application rate and leaf age on the distribution pattern of leaf SPAD readings in the rice canopy

A Soil-Plant Analysis Development (SPAD) chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008-2009)...

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Bibliographic Details
Published in:PloS one 2014-02, Vol.9 (2), p.e88421-e88421
Main Authors: Yang, Hu, Li, Jinwen, Yang, Jingping, Wang, Hua, Zou, Junliang, He, Junjun
Format: Article
Language:English
Subjects:
Age
Age composition
Agriculture
Biology
Canopies
Chlorophyll
Chlorophyll - metabolism
Environmental protection
Herbivores
Leaves
Light
Linear Models
Nitrogen
Nitrogen - pharmacology
Oryza
Oryza - drug effects
Oryza - growth & development
Oryza sativa
Photons
Photosynthesis
Photosynthesis - drug effects
Physiology
Plant Leaves - drug effects
Plant Leaves - growth & development
Rice fields
Senescence
Soil
Soil analysis
Time Factors
Transplantation
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Summary:A Soil-Plant Analysis Development (SPAD) chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008-2009) using rice plants treated with six different N application levels. N distribution pattern was determined by SPAD readings based on the temporal dynamics of N concentrations in individual leaves. At 62 days after transplantation (DAT) in 2008 and DAT 60 in 2009, leaf SPAD readings increased from the upper to lower in the rice canopy that received N levels of 150 to 375 kg ha(-1)The differences in SPAD readings between the upper and lower leaf were larger under higher N application rates. However, as plants grew, this atypical distribution of SPAD readings in canopy leaf quickly reversed to the general order. In addition, temporal dynamics of the leaf SPAD readings (N concentrations) were fitted to a piecewise function. In our model, changes in leaf SPAD readings were divided into three stages: growth, functioning, and senescence periods. The leaf growth period lasted approximately 6 days, and cumulative growing days were not affected by N application rates. The leaf functioning period was represented with a relatively stable SPAD reading related to N application rate, and cumulative growing days were extended with increasing N application rates. A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period. The rate of decrease in SPAD readings increased with the age of leaves, but the rate was slowed by N application. As leaves in the lower canopy were physiologically older than leaves in the upper canopy, the rate of decrease in SPAD readings was faster in the lower leaves.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0088421