Effects Of The Photosynthetic Characteristics Of Sarcotesta On Seed Development In Torreya Grandis 'Merrillii'

Seed development mainly depends on photosynthetic products transported from leaves or other photosynthetic organs.Torreya grandis ‘Merrillii' is an excellent cultivar of Torreya grandis Fort.ex Lind.through asexual reproduction,the development of the seed lasts 17 months(in the beginning of May to September of the following year).Sarcotesta of seed remains green until maturity,which is rich in chloroplast,synthetizes sucrose through photosynthesis,and provides carbon source for seed oil formation.Due to the rapid seed development period(from the mid April to the end of June),one year old leaves of Torreya grandis were not mature(usually at the end of April begin to sprout),it has an important significance to the development of the seed by researching the photosynthetic characteristics of sarcotesta.This study attempts to analyze the effect of photosynthetic characteristics of sarcotesta on seed development during different seed development periods from multiple perspectives,providing a useful theoretical basis to discover the potential for improving yield by photosynthesis of sarcotesta,it has an important practical significance to improve the yield.The main results are as follows:(1)This study researched seed morphologic characteristics,stomatal characteristics,photosynthetic enzyme activity and changes of chlorophyll during seed development,revealing the physiological and biochemical basis of sarcotesta photosynthesis changing during seed development.During the period of rapid expansion of seed(2016: from 0 to 98 days after protrusion of seed(DAPS);2017: from 0 to 77DAPS),the surface area of seed increased to the maximum.All of the total photosynthetic rate,the number of stomas,the related enzyme activities of photosynthetic(RuBPC enzyme activities and PEPC enzyme activities)and the contents of chlorophyll all decreased rapidly.However,in the full and mature stages,the seed size was basically unchanged,and the total photosynthetic rate and photosynthetic enzyme activity decreased slowly.Combined the analysis of total photosynthetic rate with the related parameters of photosynthesis,the result showed that the photosynthesis of sarcotesta during the process of seed development was closely related to the stomatal characteristics and photosynthetic enzyme activities of sarcotesta.(2)We studied the effect on photosynthesis,chlorophyll and photosynthetic enzyme activities by photosynthetic regulator treatments [DCMU(3-(3,4-dichlorophenyl)-1,1-dimethylurea)and EBR(2,4-epibrassinolide)] on different stages during seed development period(rapid growth period S1,enrichment period S2 and maturity period S3).Analysed the difference of the quality and oil components of mature seeds under different treatments,and explored the relationship between seed photosynthesis and seed development,and the quality formation.After DCMU treatment,in S1 compared with control,the length and width,dry matters,and sarcotesta photosynthetic enzyme activities of seed were significantly decreased,the total phenolic contents,unsaturated fatty acid contents and tannin contents of mature seed were clearly increased.In S2 after a period of DCMU treatment,seed length,seed width and dry matter did not change significantly,but the contents of unsaturated fatty acid was distinctly reduced.In S3 after a period of DCMU treatment,all indexs of seed did not change significantly.At different development stages after a period of EBR treatment,morphological indexs and the total photosynthetic rate were all not clearly changed;In S1,the total phenolic contents increased obviously and tannin contents decreased significantly.Under different treatments in different stages,the dry matter of all mature seed did not change distinctly.In summary,the effect to the dry matter accumulation of seed by the photosynthesis of sarcotesta mainly reflected in the rapid growth period,but short-term nutritional deficiencies did not affect the dry matter accumulation of mature seed;the accumulated photosynthate of seed have important effects on quality and oil formation of mature seeds in rapid growth period and filling period.