| Six species of plants(Camellia sinesis?Eurya loquaiana?Machilus pingii?Castanopsis carlesii?Symplocos grandis and S.anomala)and 29 common species were selected as the research objects in this paper.The dynamic changes of leaf size,leaf mass per area(LMA),photosynthetic pigments,non-structural carbohydrates(NSC)and their components in six species during branch and leaf expansion were studied.The relationship between NSC and its components,photosynthetic pigments and LMA was analyzed,and the causes of NSC differences in leaves during leaf expansion were discussed.At the same time,NSC and its components,photosynthetic pigments and LMA were measured in spring(May),summer(June and August)and autumn(November)respectively.Then,29 common plants were grouped according to their life-form differences,and the seasonal variations of NSC and its components,photosynthetic pigments and LMA in leaves of different life-form plants and their relationships were analyzed,compared and correlated.The main results are as follows:(1)During the whole process of leaf expansion,individual leaf area increased with the time till to a homeostasis,and the maximum value reached in late August,from 9.20 cm~2(Eurya loquaiana)to 40.81 cm~2(Symplocos grandis).LMA decreased at the initial leaf spreading period and then continuously increased.Until the end of January of the following year,it continued to increase slowly.Because of different species,the maximum value was form 82.90 g/m~2 to 152.10 g/m~2.Content of chlorophyll increased during the whole year,and maintained a higher content throughout the summer and autumn after reaching a higher value in late June,but slightly decreased in January of the following year.The contents of soluble sugar and NSC in the leaves of six plants showed similar trends,increasing gradually from the early stage of leaf expansion to the full expansion stage while starch showed the opposite trend.The content of NSC of each species is form 87.00 mg/g(S.anomala)to 163.35 mg/g(Eurya loquaiana).Except for the Symplocos grandis and S.anomala,the content of NSC increased gradually with the leaf growth process.(2)The contents of soluble sugar decreased with starch increasing,chlorophyll increased with LMA increased,the soluble sugar content positively correlated with LMA,but starch content negatively correlated with LMA(R~2=0.51-0.86,P=0.004),suggested at the late stage of leaf development,starch may convert to soluble sugar,which may due to light availability and physical activity of plants in the forest.The results suggested NSC and the component varied with leaf development stage,it on one hand related to the physical activities during leaf expansion and thickening,moreover reflected the trade-off relationships among the functional traits.(3)NSC and its components of 29 common plants have obvious seasonal variations and seasonal differences.Starch and NSC content were the highest in spring(May),while soluble sugar content was the highest in autumn(November).Evergreen,deciduous,tree,evergreen tree and evergreen shrub also showed the same seasonal variation.The leaf NSC of shrub and deciduous shrub species was mainly in spring(May)>summer(June and August)>autumn(November),while that of deciduous tree species was the opposite.Three-factor ANOVA analysis showed that season,life-type and growth-type interactions and seasonal,life-type and growth-type interactions had significant effects on seasonal changes of NSC and its components in common plants.The storage of NSC content in leaves of common plant leaves was mainly evergreen(120.94±3.54 mg/g)>deciduous(117.95±4.42 mg/g),trees(115.92±3.46 mg/g)<shrubs(123.13±4.18 mg/g),evergreen trees 112.10±3.69mg/g)<evergreen shrubs(129.79±5.95 mg/g),deciduous trees(137.95±8.52mg/g)>(112.33±4.96 mg/g).(4)There are obvious seasonal variations and seasonal differences in NSC and its components in different leaf age stages of common plants.The content of soluble sugar was the highest in autumn(November),the lowest in spring(May),and the change trend of starch was the opposite.The content of NSC in one-year-old and two-year-old decreased first and then increased with seasonal variation,while that in three-year-old decreased gradually with seasonal variation.The leaf age of evergreen shrub species also showed the same change rule,while evergreen tree species showed the same change trend with annual and biennial.Three-factor ANOVA analysis showed that leaf age significantly affected the seasonal variation of NSC and its components in leaves of common plants.The storage differences of NSC and its components in common plants were significant between annual and triennial.There were significant differences in NSC and soluble sugar storage between annual leaves of evergreen tree species,but there were no significant differences in NSC and its components storage among different leaf age stages of evergreen shrub species.The storage of NSC and its components were triennial>biennial>annual.(5)The contents of Chl a,Chl b,Chl and Car in common species of annual,biennial,triennial and deciduous species were the highest in May and June,followed by triennial and the lowest in annual.The content of deciduous species was the highest in August and November.There was no significant difference in the content of photosynthetic pigments between annual,biennial and triennial evergreen species.LMA of annual evergreen species increased continuously with seasonal variation,while that of biennial,triennial and deciduous species changed steadily.LMA of deciduous species was significantly lower than that of evergreen species.The content of photosynthetic pigments in annual leaves was correlated with NSC,which could affect the storage of NSC in annual leaves. |
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