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Diurnal dynamics of photosynthetic and transpiration rates of alfalfa under dry farming and their relationships with environmental factors

LIU Yuhua1，2; SHI Ji’an1，2; JIA Zhikuan1; HAN Qingfang1   

  1. 1College of Agronomy, Northwest Sci-Tech University of Agriculture and Forestry, Yangling 712100, China；2College of Agronomy, Henan University of Science and Technology, Luoyang 471003, China
  • Received:2005-09-14 Revised:2006-07-28 Online:2006-10-18 Published:2006-10-18

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Abstract: In this paper, the diurnal dynamics of photosynthetic rate (Pn) and transpiration rate (Tr) of four years planted alfalfa under dry farming, as well as those of photosynthetic active radiation (PAR), CO2 concentration in field (Ca), relative humidity (RH) and air temperature (Ta) were measured , and the relationships between the diurnal dynamics of Pn, Tr and climatic factors were analyzed by correlation coefficient, path coefficient, and decision coefficient analyses. The results showed that Ta had the greatest effect on the diurnal dynamics of Pn, while RH, PAR and Ca affected Pn mainly through their acting on Ta. PAR had the greatest effect on the diurnal changes of Tr, and RH, Ta and Ca affected Tr indirectly by acting on PAR. For the characteristics of photosynthesis and transpiration, PAR was the primary determining factor, and Ta was the main limiting factor.

Key words: Winter wheat, Dry matter, Accumulation and distribution, Simulation