The Morphogenesis,Structure And The Main Chemical Compositions Of The Endotesta In Ginkgo Biloba L.

Ginkgo biloba L.is an important economic and ecological tree.The previous studies on ginkgo seed coat mostly focused on the episperm and mososperm,but less on the endotesta.Based on optical microscope and transmission electron microscope,this study studied the structure and characteristics of the mature seed endotesta by microscopic CT imaging and scanning electron microscope,and the detection of the main components by routine methods.The main results were as follows:1 Discovery of the morphogenesis of endotesta:（1）The main source of endotesta was inner integument and part of the nucellus.The Megaspore membrane was also involved in the morphogenesis of the endotesta.（2）The conoid structure was essentially the inner integument at the micropyle end.（3）In the middle of April,the inner integument and its adjacent nucellar tissue had differentiated;in the middle of May,the whole inner integument structure differentiated obviously;in the late of June,the inner integument and its adjacent nucellar tissue entered the stage of programmed death;in the early of July,the whole inner integument structure became thinner;from the middle of August to the early of September,the integument and nucellar cell were obviously changed into membrance,and the endotesta was basically formed.（4）The development of the endotesta was a typical PCD process,which showed the typical PCD characteristics such as cell shrinkage,nuclear concentration and edge localization,and the destruction of the overall structure of the cell.2 Direct observation and micro CT imaging were used to characterize the endotesta structure,it found that:The endotesta from the middle line to the chalazal end was a single gray white chartaceousstructure with a thickness of about 19.6μm and a loose texture.From the middle line to themicropyle end,the endotesta was divided into two layers,the lateral endotesta was close to themesotesta with a thickness of about 9.1μm and the medial endotesta was close to the seed kernelwith a thickness of about 10.4μm,all of them were translucent and reddish brown dense membrane structures;The ultramicrostructure of the intact endotesta was obtained by SEM:at the chalazal end,the surface of the endotesta was irregular,with gullied gaps,and the wax was thicker;at the micropyle end,the two layers of the inner testa were similar,and the wax and tumor layers were thinner.3 The main chemical compositions of endotesta were as follows:（1）Several basic components in the endotesta were determined,its moisture content was37.40%,ash content was 2.33%,protein content was 9.94g/100g,fat content was 3.35g/100g,soluble sugar content was 4.09g/100g.（2）There were five major elements in the endotesta:potassium（18353.43mg/kg）,calcium（5045.68mg/kg）,magnesium（2294.02mg/kg）,phosphorus（696.63mg/kg）,sodium（456.83mg/kg）,and 10 trace elements,such as iron（136.24mg/kg）,boron（57.52mg/kg）,zinc（43.12mg/kg）,barium（11.09mg/kg）and so on.（3）The contents of 7 kinds of vitamins in the endotesta were determined,including 17.22μg/g of VE,7.26μg/g of VB₁ and 6.43μg/g of VB₂,which were 2.4-12.9 times of kernel.（4）The endotesta contained 17 kinds of amino acids,among which aspartic acid and glutamic acid were abundant;18 kinds of fatty acids,mainly saturated fatty acids.