Effect Of Different Light Quality On Photoinhibition Of Photosynthesis In Strawberry Leaves

Strawberry is one of the most important baccate fruits in China.Its yield and cultivated area reached to 1338 thousands tons and 82 thousands hectares respectively in 2003,which ranked the first in the world.After entry of China into WTO,our domestic strawberry market will surely face the competition from abroad.Therefore,the breeding and production of high quality strawberry fruit is urgent.During the course of cultivating strawberry plants,we are often confronted with the problems as follow:(1)Light photoinhibition.Strawberry is thought to be a shade adapted plant.Leaves of strawberry plants grown in open field suffer from photoinhibition and photooxidative damage which may result in death in high light that usually occurs during the summer;(2)Light shortage and light quality.Both light intensity and light quality are affected when light through glass and plastic film in protected cultivation,and little is known about its effects on the characteristics of photoinhibition in strawberry leaves,especially light quality chang.To clarify the mechanism of photoinhibition and responses of growth and fruiting to light quality,we studied the following physiological aspects(1)Response of photosynthesis to high light and its mechanism in strawberry leaves grown in different light quality.(2) Effects of light quality on the antioxidant system in strawberry leaves.(3)Effect of different light quality on photosynthesis and chlorophyll fluorescence in strawberry leaves grown in different light quality.The results were summarized below.1)The results showed that the apparent quantum efficiency(AQY),maximal photochemical efficiency of PSⅡ(Fv/Fm)and maximal fluorescence(Fm)decreased in high light by the percent of the order:red film＞neutral film＞green film＞blue film, which were correlated with the proportion of blue and ultraviolet in different light quality negatively.Our results suggest that strawberry leaves grown under red film is sensitive to photoinhibition,but those grown under blue film is on the contrary.2)Studies showed that maximal photochemical efficiency of PSⅡ(Fv/Fm),amount of inactive PSⅡreaction centers(Fi-Fo)were correlated with red/blue ratios positively,but chlorophyll(a/b)ratios were correlated with red/blue ratios negatively.Carotenoid contents were in the order:blue film＞green film＞neutral film＞red film,which were correlated with red/far-red ratios negatively.Light quality play an important role in the regulation of PSⅡwhich involved in the laminae of strawberry,phy(the receiptor of red light and far red light)and cry(the receiptor of blue light)take abroadly part in the regulation of the development of strawberry laminae photosynthesis organ.3)Growth and fruiting of strawberry are also regulated by light quality.The optimum light quality for leaf and petiole growth was green film,red film was in the next place,and the last was bule film.The proportion of total plant dry biomass allocated to fruits, crowns and roots under blue film was the greatest,the next was red film,and the last was green film,but that to leaves and petioles under green film was the greatest,the last was blue film,the rest were similar.The yield per plant under red film was the greatest, the next was blue film,and the last was green film.Therefore,by utilizing light to accommodate the growth and outcome of the strawberry can help to achieve fertility,high quality and good effect.As a new technology which needs low cost whithout contaminative to environment,it has both application extensively and research and development foreground.4)These studies showed that different light quality and high irradiation affected photosynthesis and chlorophyll fluorescence in strawberry leaves,and yield of strawberry.So these mechanisms of photoinhibition and responses of growth and fruiting to light quality is needed to understand how light influences its photosynthesis in protected cultivation.The yield per plant and fruit weight per one under red film was the greatest,and the photosynthetic characteristics of strawberry were correlated with red/blue ratios positively.So it is beneficial to regulating growth and fruiting for strawberry protected cultivation in red light.The proportion of total plant dry biomass allocated to crowns and roots under blue film was the greatest,and strawberry leaves grown under blue film is less sensitive to photoinhibition.The results as above may play an important role in breeding lusty seedling.