Nutritional and developmental influences on productivity and components of crop light use efficiency

Steve Lindner1, Wei Xue1, Bhone Nay-Htoon2, Maren Dubbert2, Dennis Otieno1, Jonghan Ko3, Hiroyuki Muraoka4, Christiane Werner5, Peter Harley1, Jürgen Dengler1, John Tenhunen1
1 Plant Ecology, BayCEER, University of Bayreuth
2 Agroecosystem Research, BayCEER, University of Bayreuth, 95440 Bayreuth, Germany
3 Department of Applied Plant Science, Chonnam National University, 500757 Gwangju, South Korea
4 River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu, 501-1193 Japan
5 Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95440 Bayreuth, Germany

P 2.4 in Elements, tracers, chemical species: All about CHEMISTRY and the elemental needs of life

Introduction

Light use efficiency (LUE) plays a vital role in determination of crop biomass and yield. Important components of LUE, i.e. canopy structure, nitrogen distribution, photosynthetic capacity and CO2 diffusion conductance were investigated in paddy rice (Oryza sativa L.) grown under low, normal and high supplemental nitrogen (0, 115, 180 kgN ha-1).

Material and Methods

The experimental site is located at the agricultural fields of Chonnam National University, Gwangju, S. Korea. Four plots were established in the middle of the paddy fields (511 - 1387 m2) for each nutrient treatment to monitor diurnal canopy CO2 gas exchange with a set of transparent and opaque chambers. CO2 response curves, diurnal gas exchange and chlorophyll fluorescence measurements at four different heights in the canopy were conducted using a portable gas-exchange system (GFS-3000, Walz). Radiometric measurements were carried out over growth season by a portable multispectral radiometer (Cropscan Inc.). 

Results

Photosynthetic characteristics varied linearly with leaf nitrogen content, independent of treatment and canopy position, so differences in photosynthesis were due to differences in N allocation. Early in the season, leaves in the fertilized treatments had higher photosynthetic rates due to higher leaf N content leading to larger amounts of rate-limiting photosynthetic proteins, which gave them an early head start and boost in productivity and leaf area index (LAI), bringing increases in canopy light absorption. Enhanced LAI in fertilized plots throughout the growing season was related to greater leaf number and leaf area per planted bundle and a larger leaf area in the upper canopy (LAUC).

Conclusions

 

Differences in carbon gain and biomass accumulation under differing N fertilization were associated primarily with resource allocation associated with canopy leaf area development rather than leaf morphological or physiological properties.



Keywords: canopy structure; CO2 diffusion conductance; light use efficiency; nitrogen fertilization; photosynthesis; rice crop
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