Characteristics of Light Environment in Modern Greenhouse
The characteristics of light environment were investigated systemically based on meteorologic data from December 2002 to April 2004 in modern greenhouse.The results indicated that PAR (photosynthetic active radiation) outside greenhouse in winter-spring (from November to next March) is insufficient and low with continuous cloudiness or rain.The change of PAR inside changed with PAR outside synchronously,and there was significantly linear correlation between PAR inside and PAR outside (r=0.972~(**)).PAR both inside and outside in clear day are higher than that in cloudy or rain day. Average transparent rate of experiment glasshouse is 50.6%. The main causes led to decline of transparency of glasshouse covering materials and how to improve it were also discussed in this paper.