Comparative Study On Annual Growth Rule Of Leaves Of Juglans Sigillata L.’Shengshuang’ And Juglans Regia L.’Yanyuanzao’

Juglans spp.is an important nut species in the world,and its area and yield rank first among dried fruits.Walnut has a long history of cultivation in China and is widely distributed in 27 provinces,municipalities and autonomous regions.There are two kinds of walnut cultivated as fruit trees:Juglans regia L.and Juglans siggillata L.The common walnut is mainly distributed in the major producing areas of the world and is the main cultivated species in the north of China.The common walnut has the characteristics of cold tolerance,drought resistance and waterlogging resistance,thin shell and full kernel,and excellent quality.Pickled walnut,also known as deep-grained walnut and Yunnan walnut,is mainly distributed in Yunnan,Guizhou,Sichuan,Tibet and Guangxi regions in southwest China.It is the main cultivated variety in southwest China with thin shell,high yield of benevolence and oil and excellent quality.Leaves are important places for plants to carry out photosynthesis and produce nutrients needed for plant growth.In this paper,the annual growth and development process of walnut leaves and the influence of environmental conditions on it were studied.The aim was to explore the relationship among leaf growth law,leaf area,chlorophyll content,photosynthetic characteristics,meteorological factors and phenology,in order to provide theoretical support for the study of biological characteristics and cultivation technology system of walnut.The conclusion is as follows:1.Annual variation of leaf areaThe leaves of’Shengshuang’(Juglans sigillata L.variety‘Shengshuang’,the same below)began to spread on April 4,and the average area of leaves reached the maximum of 52.33cm~2on June 2,lasting for 59d.The rapid growth period of leaf area was from April 4 to May 6,and the annual growth cycle of leaves was about 212d.’Yanyuanzao’(Juglans regia L.variety‘Yanyuanzao’,the same below)began to spread leaves on March 20,and the average leaf area reached a maximum of 30.58cm~2on April 29.The rapid growth period of leaves was from March 20 to April 20,and the annual growth cycle of leaves was about 216d.There were significant differences in the growth state of walnut leaves except germination stage between the two cultivars.The average area of’Shengshuang’and’Yanyuanzao’leaves was 13.71cm~2and9.42cm~2at flowering stage.In the rapid growth period of young fruit,the average leaf area of’Shengshuang’was 44.88cm~2,and that of’Yanyuanzao’was 27.91cm~2.In the slow growth stage,steady growth stage and mature stage,the average area of’Shengshuang’leaves was 52.33cm~2and that of’Yanyuanzao’was 30.58cm~2.In the deciduous period,the average leaf area of’Shengshuang’was 18.72cm~2,and that of’Yanyuanzao’was 30.58cm~2.2.Annual changes of leaf chlorophyllThe average relative content of chlorophyll in the leaves of’Shengshuang’walnut was 11.45 on April 4 when the leaves were spreading.From April 4 to June 20,the chlorophyll increased rapidly.On September 5,the maximum appeared at 44.96,and on September 17,the chlorophyll content began to decline.The average value of chlorophyll in’Yanyuanzao’walnut was 12.63 on March 2 when the leaves began to spread,and the chlorophyll increased rapidly from March 20 to June 15,and peaked at 42.44 on July 27,and began to decline on September 12.3.Annual changes of leaf photosynthetic characteristicsThe annual variation curves of the net photosynthetic rate of’Shengshuang’and’Yanyuanzao’were similar,which maintained relatively stable in the early stage.When the chlorophyll growth was higher,the photosynthetic rate also increased and maintained for a long period of time,providing photosynthates for the tree body.The decline occurred on September 12 and September 5,respectively.The net photosynthetic rates of’Shengshuang’and’Yanyuanzao’were different in each phenological period,and there were significant differences.The annual net photosynthetic rate of Shengshuang was higher than that of Yanyuanzao.4.Leaf area change,photosynthesis and phenologyThe fastest growth period of’Shengshuang’leaf area was from April 4 to May 6,and’Yanyuanzao’was from March 20 to April 20,both of which were in the period of flowering,shooting and rapid growth of young fruit.The fastest growth stage of chlorophyll content in’Shengshuang’leaves was from April 4 to June 20,and the fastest growth stage of’Yanyuanzao’leaves was from March 20 to June 15,both of which were at flowering stage to slow fruit growth stage.The leaf area of’Shengshuang’and’Yanyuanzao’remained stable from June 2 to October 12 and from April 29 to October 1,respectively,in the rapid growth stage of young fruit to maturity stage.The chlorophyll content of’Shengshuang’and’Yanyuanzao’leaves remained stable from June 20 to September 17 and from June 15 to September 12,respectively,and the phenology stage was from slow growth stage to mature stage.The leaf area of’Shengshuang’and’Yanyuanzao’both began to decrease in October,and the chlorophyll content began to decrease in September,when the fruit was from maturity to deciduous stage.The rapid growth period of net photosynthetic rate of’Shengshuang’was from June 2 to June 30,during the rapid growth period of young fruit and fruit growth period,while the rapid growth period of’Yanyuanzao’was from June 15 to June 30,during the slow growth period of fruit and fruit growth period.The period of maximum annual photosynthetic rate of’Shengshuang’was from June 30 to September 12,when fruit growth was stable and fruit maturity,while the period of’Yanyuanzao’was from June 30 to September 5,when fruit growth was stable and fruit maturity.The net photosynthetic rate of’Shengshuang’and’Yanyuanzao’began to decrease gradually on September 12 and September 5,respectively,when the fruit was from maturity to deciduous stage.5.Relationships among leaf area changes,photosynthetic parameters and meteorological factors.The growth rate of’Shengshuang’young leaf area was positively correlated with air humidity and air temperature,while the added value of’Yanyuanzao’young leaf area was negatively correlated with air humidity.The increase of chlorophyll content in’Shengshuang’young leaves was positively correlated with air humidity,air temperature and photosynthetically active radiation,while the increase of chlorophyll content in’saline-source early’young leaves was correlated with lightThe combined effective radiation is negatively correlated.The net photosynthetic rate of Shengshuang was positively correlated with the photosynthetic active radiation,and the photosynthetic active radiation was more sensitive to the net photosynthetic rate.The correlation between net photosynthetic rate of’Yanyuanzao’and air temperature is more significant than’Shengshuang’.6.The diurnal variation curve of the net photosynthetic rate of the young leaves of’Shengshuang’showed an obvious unimodal pattern,and the net photosynthetic rate continued to increase from 8:00 to 14:00,and then gradually decreased to the lowest after 14:00.The diurnal variation of net photosynthetic rate of adult leaves showed an obvious bimodal curve,which continued to rise rapidly from 8:00 a.m.to 11:00 a.m.,and reached the highest point at 11:00 a.m.From 11:00 to 12:00,the net photosynthetic rate began to decline.At 12:00,the trough occurred,and the phenomenon of siesta occurred.From 12:00 to 15:00,it began to rise,and reached the highest point of the day at 15:00,and gradually dropped to the lowest point from15:00 to 18:00.