Effects of Soil Moisture and Light Intensity on Photosynthetic Rate of Morus alba

Key words: 
• Morus alba /
• soil moisture /
• light intensity /
• rate of photosynthesis

Abstract: Morus alba was pot cultured with 6 treatments with a 10% gradient of soil relative water content（ SRWC） or soil moisture content from 30%- 80% to observe light response parameters,rate of net photosynthesis,and other parameters to explore the combined effects of light intensity and soil moisture on net photosynthesis rate of M. alba leaves by constructing a mathematical model for the rate of net photosynthesis and environmental factors. The observations showed that light intensity gave a significant positive correlation with the rate of net photosynthesis when the soil relative water holding capacity was in the range of 40%- 80%. Both the light intensity and soil moisture had impacts on the rate of photosynthesis,and the impact varied with soil moisture content. Among the soil moisture treatments the rate of photosynthesis tended to show a similar response to light intensity,and the response increased rapidly first with the light intensity,and then slowly concurrent with a light saturation phenomenon. At low soil moisture content,soil moisture had a dominant impact on the rate of net photosynthesis,while at higher soil moisture content,light intensity had a dominant impact on the rate of net photosynthesis.The comprehensive impacts of light intensity and soil moisture on the rate of photosynthesis could be expressed by a exponential mode,and the dominant factor affecting the rate of net photosynthesis was shifted from the soil moisture to the light intensity at a threshold of soil moisture content of 51. 17%.