Effect Of Canopy Micro-climate On Growth,Development And Yield Of Xanthoceras Sorbifolium Bunge

To clarify the relationship between canopy micro-climate and phenophases,phenotypic traits and photosynthetic characteristics of Xanthoceras sorbifolium Bunge,the leaf curtain was divided into different areas.The canopy micro-climate factors were continuously observed throughout the year,including light intensity,temperature,and relative humidity.At the same time,the phenophases and phenotypic traits in different leaf curtain areas were investigated to reveal the growth rhythm of X.sorbifolium.In addition,the photosynthetic daily dynamic curves and the light response curves were determined to compare photosynthetic characteristics of leaves in different areas.Correlation analysis and multiple regression analysis were used to show the effect of canopy micro-climate on growth,development and yield of X.sorbifolium.The results could provide a theoretical basis for the development of subsequent cultivation management measures.The main results were as follows:(1)When the leaf curtain was not formed or after falling leaves,the trend of light intensity was: upper outer > upper inner > under outer > under inner.During the leaf curtain formation,the light intensity was: upper outer > under outer > upper inner > under inner.The temperature showed the same trend as follows in different periods: upper outer > upper inner > under outer > under inner,which was opposite to the change trend of relative humidity.(2)Significant difference was observed in the phenophases among different leaf curtain areas within the canopy.The maximum and minimum differences were observed in the bud enlargement stage(8 days)and early flowering stage(3 days),respectively.The longest total growth period(199 days)and the shortest total flowering period(7 days)occurred in the upper outer area from the south direction.(3)In different directions,the latitude and longitudinal diameter of flower buds were similar as below: upper outer > upper inner > under outer > under inner.Most of the traits including inflorescences length,the number of fertile flowers,the length and base diameter of current year branches,the number of fruits,fruit yield,the number of seeds and seed yield presented the same change pattern as follows: upper outer > under outer > upper inner > under inner.In addition,the above-mentioned traits in the southeast areas were higher than that in the northwest areas.(4)The diurnal variations of net photosynthetic rates of each area in different phenophases presented asymmetric bimodal curve characteristics,with obvious “midday depression” phenomenon.The maximum and minimum photosynthetic parameters were observed in fruit maturing stage and deciduous stage,respectively.Except the light saturation point,the other photosynthetic parameters exhibited the same trend as follows: upper outer > under outer > upper inner > under inner.(5)In contrast with phenophases,most phenotypic traits and photosynthetic parameters were positively related to the annual average light intensity and temperature,but negatively related to the annual average relative humidity.In the areas with high light intensity,high temperature,and low relative humidity,the growth period was longer and the light energy utilization efficiency was higher.In above areas,the micro-climate was conducive to the development of X.sorbifolium.