Effect Of Environmental Factors On The Growth And Photosynthetic Characteristics Of Davidia Involucrata Seedlings

Davidia involucrate Baill is a rare and endangered plant endemic to China surviving from the Tertiary, and it is significant to find out the limiting factors of off-site preservation of D. involucrate. The study begin in May 2014 and ended in September 2015. Effect of soil matrixes, moisture and light intensity was obvious to seedlings, so the reflection of D. involucrate seedlings photosynthesis and growth on the environment directly influenced seedlings introduction and updated dynamically of D. involucrate populations. We analysed the response of D. involucrate seedling to the environment under different gradients, to study the adaptive strategy of D. involucrate seedlings.The results suggest that:(1) The plant height and ground diameter dropped significantly at the end of drought processing..Water stress decreased leaf biomass, and increased the root biomass and root cap ratio. With the reducing of water, leaf nitrogen content and root nitrogen contenthave a modest increase trend. The effects of soil matrixes on the height and net photosynthetic rate (Pn) in seedlings was not significant. That is to say, D. involucrate seedlings issensitive to drought stress, and seedlings has a wide adaptation range of soil matrix. (2) The net photosynthetic rate (Pn) of D. involucrate varied as a bimodal curve with a’midday depression’phenomenon in full bright light, and as a unimodal curve in the shading treatments. With shade, plants had higher photosynthetic rate (Pmax), apparent quantum yield (AQY),water use efficiency (WUE) and light use efficiency (LUE), lower light-compensation point and dark respiration rate. Plants grown in the shade treatment had greater SLA and biomass, lower R/T. We concluded that D. involucrate had the ability to adjust to shade in leaf photosynthetic and growth characteristics. Therefore, D. involucrate seedlings are shade tolerant. (3) The midday depression phenomenon of photosynthesis of D. involucrate seedlings can be eased by increasing the air humidity around the leaf blade, high or low humidity will reduce the net photosynthetic rate (Pn) and transpiration rate (Tr) of the plants, the proper humidity between 50% to 70%.