Variations of leaf shape coefficients of winter wheat
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DOI:10.7606/j.issn.1000-7601.2017.05.01
Key Words: winter wheat  leaf area  leaf shape coefficient  leaf length  leaf width  variation
Author NameAffiliation
ZHOU Yuan-gang Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China
Xi'an Water Group Co., Ltd., Xi'an, Shaanxi 710061, China
Institute of Water-saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, Shaanxi 712100, China 
YAO Ning Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China
Institute of Water-saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, Shaanxi 712100, China 
FENG Hao Institute of Water-saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, Shaanxi 712100, China
Institute of Water and Soil Conservation, Chinese Academy of Science and Ministry of Water Resource, Yangling, Shaanxi 712100, China 
BAI Jiang-ping Gansu Key Laboratory of Crop Genetic and Germplasm Enhancement, Gansu Agricultural University Agronomy College, Lanzhou, Gansu 730070, China 
ZHANG Ti-bin Institute of Water and Soil Conservation, Chinese Academy of Science and Ministry of Water Resource, Yangling, Shaanxi 712100, China 
HE Jian-qiang Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China
Gansu Key Laboratory of Crop Genetic and Germplasm Enhancement, Gansu Agricultural University Agronomy College, Lanzhou, Gansu 730070, China 
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Abstract:
      In this study, the temporal and spatial variations of α values of winter wheat had been investigated through a field experiment conducted from October 2014 to June 2015. A total of six wheat cultivars (varieties) (two early ripening, two medium ripening, and two late ripening) were involved. The whole growth season of wheat was divided into six different stages, i.e. emergence, greening, jointing, heading, flowering and maturity. Wheat plants were randomly collected and all leaves were cut off and measured for their length, width, and area with a digital leaf area scanner. Then, α values were calculated for each leaf. The variations of α values were analyzed for different growth stages, among different wheat cultivars, and among different leaves of a single plant. The results showed that α value ranged from 0.59 to 0.71 and varied at different growth stages. It increased with fluctuations from emergence to flowering stage, and then decreased. The uncertainties of α values, measured by standard deviation and coefficient of variation, decreased first and then increased slightly. Within a single plant, α values varied at different stages but remained relatively stable at flowering stage. The uncertainty of α value increased after flowering. Among different wheat cultivars of various ripening traits, α values were significantly different at jointing, heading and flowering stages, but not significantly different at emergence, greening and maturity stages. Thus, it is better to adopt various α values at different growth stages so as to improve the accuracy of simulation and prediction of leaf area of winter wheat. Based on linear regression analysis of leaf area and product of leaf length and width of 1 485 leaf samples of six different wheat cultivars, the general value of α was about 0.66. Then, when simulating wheat leaf areas with the model of LA=0.66×L×W, the relative root mean square error (RRMSE) and absolute relative error (ARE) were 4.40% and 13.05%, respectively. The accuracy was the highest among the five different models investigated for estimation of wheat leaf area. Thus, this model was recommended for the estimation of wheat leaf area and leaf area index in future field studies.