Abstract:

 Compensation point to CO₂ is one of the key parameters for crop growth model. Systematic measurements of parameters for physiological-ecology of different varieties of winter wheat before 1949 and from1949 to 2005 in North China were conducted using a Licor-6400. Based on these measurements, rectangular hyperbolic photosynthetic models of different winter wheat varieties in North China involving the function of CO₂ were fitted in order to determine compensation point to CO₂ in different varieties in different time. The results indicate that the compensation point to CO₂ decreases with increase of photosynthetic photon flux density (PPFD) in the North China. Under 800 μmol·m^-2·s^-1 PPFD conditions, the compensation point to CO₂ of the wild variety is the highest, reaching 123.40 μmol·mol^-1. During 1949-2005, the compensation point to CO₂ varies obviously with varieties, with the highest value of 107.07 μmol·m^-2·s^-1 for Taishan No.1 variety and the lowest value of 57.25 μmol·mol^-1 for Hongtutou variety. Difference of maximum and minimum values between different varieties of winter wheat reaches 49.82 μmol·mol^-1, and it suggests that compensation point to CO₂ changes significantly with evolution of winter wheat varieties in North China. The study establishes rectangular hyperbolic photosynthetic models of seven typical winter wheat varieties in the North China involving the function of CO₂, and identifies the compensation point to CO₂, which provide the basic data set to develop crop models for evaluation of impact of climate change on agriculture in North China.

Key words:  Compensation point to CO₂, Winter wheat, Parameters for physiological-ecology, Crop growth model