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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR AND GENETIC ENHANCEMENT OF ABIOTIC STRESS TOLERANCE IN SORGHUM

Location: Plant Stress and Germplasm Development Research

Title: A simple quantitative model to predict leaf area index in sorghum

Authors
item Narayanan, Sruthi -
item Aiken, Robert -
item Xin, Zhanguo
item Prasad, Vara -
item Yu, Jianming -

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2013
Publication Date: June 1, 2014
Citation: Narayanan, S., Aiken, R., Xin, Z., Prasad, V., Yu, J. 2014. A simple quantitative model to predict leaf area index in sorghum. Agronomy Journal. 106(1):219-226.

Interpretive Summary: Leaf area index (LAI) is a very important biophysical paramenter for canopy architecture. It has a prominent role in characterizing crop growth, radiation, and water use efficiency, and abiotic stresses at the canopy level. Determination of LAI is a complicated process, involving many measurements with sophisticated instruments. Furthermore, it is impossible to determine LAI on a daily basis, which is required to calculate solar radiation use efficiency and other fundamental canopy formation processes. We have developed a simple quantitative model to predict LAI for sorghum (Sorhum bicolor (L.) Moench) from emergence to flag leaf stage. Measurements for two cropping seasons included LAI, leaf number, leaf length, maximum leaf width, and leaf area for eight sorghum genotypes under water-and nutrient-sufficient field conditions. LAI was calculated from an algorithm developed to consider the area of mature leaves (leaves with a ligule/collar), area of expanding leaves, total leaf area per plant and plant population. The leaf shape factor (slope of regression of leaf area on product of leaf lenght and maximum width) was constant (0.73 in 2009 and 0.81 in 2013) or all mature leaves across all genotypes. Phyllochron varied among genotypes. Slope of regression of modeled LAI on observed LAI varied for photoperiod sensitive (PPS) and insensitive (non-PPS) genotypes in 2010. A good correlation was found between modeled and observed LAI with coefficient of determination (R2) 0.96 in 2009 and 0.99 (non-PPS) and 0.95 (PPS) and 0.95 (PPS) in 2010. The proposed model contributes a new method to calculate the area of expanding leaves and can be used to quantify LAI at any given day of the vegetative growing season based only on growing degree days and making use of generic coefficients demonstrated in this work.

Technical Abstract: Canopy architecture has a prominent role in fundamental processes of crop growth including light interception and photosynthesis. A widely used bio-physical parameter to quantify vegetative canopy architecture is leaf area index (LAI). The objective of this study was to develop a simple quantitative model to predict LAI for sorghum (Sorghum bicolor (L.)Moench) from emergence to flag leaf stage. Measurements for two cropping seasons included LAI, leaf number, leaf length, maximum leaf width, and leaf area for eight sorghum genotypes under water - and nutrient - sufficient field conditions. LAI was calculated from an algorithm developed to consider the area of mature leaves (leaves with a ligule/collar), area of expanding leaves, total leaf area per plant and plant population. The leaf shape factor (slope of regression of leaf area on product of leaf length and maximum width) was constant (0.73 in 2009 and 0.81 in 2010) for all mature leaves across all genotypes. Phyllochron varied among genotypes. Slope of regression of modeled LAI on observed LAI varied for photoperiod sensitive (PPS) and insensitive (non-PPS) genotypes in 2010. A good correleation was found between modeled and observed LAI with coefficient of determination (2) 0.96 in 2009 and 0.99 (non-PP) and 0.95 (PPS) and 0.95 (PPS) in 2010. The proposed model contributes a new method to calculate the area of expanding leaves and can be used to quantify LAI at any given day of the vegetative growing season based only on growing degree days and making use of generic coefficients demonstrated in this work.

Last Modified: 10/1/2014
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