| Quercus glauca Thunb.belongs to Quercus section Cyclobalanopsis,Fagaceae It is the tall evergreen tree with strong ecological adaptability,and it is one of the important constituent tree species and precious timber tree species in the subtropical monsoon evergreen broad-leaved forest in China.Q.glauca acorn is rich in starch and tannin,and is an important economic forest tree species.It is also the main food source of fruit-eating wild animals and an extremely important link in the subtropical forest food chain in East Asia.This paper mainly carried out the observation of morphological anatomical characteristics and seed germination of Q.glauca determine the content of starch and tannin in acorn.The germination characteristics of different populations of Q.glauca,the effect of different cotyledons deletion at different degrees on seed germination,the morphological characteristics of acorn and the differences in starch and tannin content were analyzed.The differences in growth,morphological characteristics of Q.glauca acorn,seed starch and tannin content,seed germination habits of Q.glauca populations in different geographical areas were discussed,in order to reveal the regional adaptation mechanism of Q.glauca and provide a preliminary research basis for the collection of Q.glauca germplasm resources,breeding of elite varieties and the conservation,management and restoration of evergreen broad-leaved forests in China.The main results are as follows:(1)Morphological characteristics of Q.glauca acorn and germination characteristics of Q.glauca seedsAfter the Q.glauca female flower was fertilized at the end of June and early July,1(2)of the 6 ovules developed.In the early stage of acorn development,the width of acorn was longer than the length.As the acorn developed,the acorn length to width ratio gradually increased,and the proportion of the acorn covered by the shell gradually decreased.The thickness of the peel increased first and then became thinner.The color of the embryo gradually changed from transparent to opaque milky white or light yellow.Different groups and individuals have different acorn forms,the 1000-grain weight of Q.glauca mature acorn was 1151.75 ± 0.33g,the length was 16.78 ±1.70mm,the width was 11.12± 1.47mm,the length to width ratio was 1.53±0.20 and the single acorn weight was 1.15± 0.40g.Among them,the Yuanling population in Hunan province had the smallest and lightest acorns;the Jingdong population in Yunnan province had the largest and heaviest acorns;the comprehensive variation coefficient of the phenotypic traits of the Taohua Island population in Zhejiang province was the largest(17.38%),and the comprehensive variation coefficient of the Lianyuan population in Hunan province was the smallest(9.82%).The correlation between the weight,length,width and aspect ratio of acorns was significant,the correlation coefficient between single acorn weight and width was the largest(0.888).The results of the seed germination test showed that seeds of Q.glauca unpeeled germinated on 12d,and the germination rate reached its peak on 44d;after peeling off the pericarp,the seeds of the cotyledons that have not been removed were germinated in 3d;the seeds for 1/3 and 2/3 cotyledons were excised and the germination time was 2d and 1d,respectively.However,the more the cotyledon was removed,the weaker the seed growth in the later period.This indicates that Q.glauca seeds had dormant properties,and the contents of cotyledons resisted seed germination.(2)Enrichment characteristics of starch and tannin in acornThe determination of starch and tannin content in acorns at different growth and development stages showed that the starch accumulation reached the peak(49.91 ±2.10%)from the end of October to the beginning of November,but the tannin content was stable at 1.49±0.02%.The results of determination of seed starch and tannin content of different groups showed that the average values of starch and tannin content were 53.70 ± 6.66%and 1.41±0.03%,respectively.The content of seed starch and tannin among the groups was significantly different(P<0.05).Among them,the Putuo Mountain population in Zhejiang province had the highest seed starch content(58.21±6.62%)and the Jinggu population in Yunnan province had the lowest seed starch content(46.76±3.77%);the seed starch content of the Taohua Island population in Zhejiang province had the largest variation(CV=17.47%),and the Jinggu population in Yunnan had the smallest variation(CV=8.07%).Jinggu population in Yunnan province had the highest seed tannin content(1.45±0.01%),while Jingdong population in Yunnan province had the lowest seed tannin content(1.38±0.03%);Xinning population in Hunan had the highest seed tannin content variation(CV=2.65%);the seed tannin content of Jinggu population in Yunnan province had the smallest variation(CV=0.87%).The starch content in Q.glauca seeds was significantly negatively correlated with tannin content(r=-0.271,P=0.046).Starch content was significantly positively correlated with longitude(r=0.347,P=0.009)and latitude(r=0.341,P=0.011),and extremely significantly negatively correlated with the monthly mean temperature difference(r=-0.337,P=0.012).The correlation of seed tannin content with morphological indicators,geographic location and climatic indicators was not significant. |
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