| Thin-shelled amygdala and thick-shelled amygdala were used as test materials to observe the structural differences of endocarp during the development of amygdala,and the physicochemical properties of endocarp during the development of amygdala were studied.This paper aims to provide a theoretical basis for the exploration of high-quality germplasm materials and shell development mechanism of thin-shell amygdala in almonds,and to reserve for the breeding of thin-shelled amygdala.The main test results are as follows:(1)(1)The inner peel of thick-shelled almonds is thinner-shelled and lignified earlier.Thick-shelled amygdala ’4-8’ and ’3-2’ have completely lignified peels within 51 days of flowering.The thin shell is not yet fully lignified;The observed lignification sequence gradually hardens from the tip to the tail and from the suture to the ridge.(2)Within 30 days after flowering,the pericarp in the peel has obvious boundaries,the volume and cell wall thickness of the mesocarp are greater than the endocarp cells,the endocarp is smaller than the mesocarp cells,the cells are closely arranged,the duct of the mesocarp first appears lignin deposition,and the dyeing order in the endocarp is observed: ducts,cell clusters,the whole endocarp.(3)Scanning electron microscopy can observe that the tonsils cell wall is significantly thinner 30 days after flowering,and the supporting ability of the cell wall is weak.The thickness of the cell wall of the inner fruit of thick-shelled almonds is greater than that of thin-shelled amygdala,lignin first appears at the corner of the cell,and then gradually accumulates,the cell wall is significantly thickened 44 days after’thick 4-8’ flowering,and the secondary cell wall appears,the marginal porous structure on the cell secondary wall can be seen,and the macrofibril filaments with a smaller diameter can be seen in the 44 days after the flowers of thin-shelled almonds,and the macrofibril filaments are distributed on it in granular form with macrofibril filaments as the skeleton.Forty-four days after flowering,thin-shelled amygdala’15-12’ appears with a large diameter and hollow vascular bundles.Thin-shelled tonsils at the same time have larger intercellular spaces than thick-shelled tongdalas.(4)The thickening of the cell wall is accompanied by the accumulation of microfibrils and the continuous deposition of cell wall materials to form secondary walls,and the early stage of the endocarp often has a higher concentration of cytoplasm,and then with the growth and development of the endocarp,the cytoplasmic concentration in the endocarp cells becomes lower,and the cell wall material deposited increases significantly 44 days after flowering,becoming a secondary cell wall.The flocculent proteins in the vacuole form spherical proteosomes,while there are a number of starch granules with unequal electron densities and low electron densities,usually distributed along the cell wall.(5)The contents of lignin,cellulose and hemicellulose increased in the process of development of the pericarp of almonds,and the lignin content of the endocarp of almonds was 42.52～273.10mg/g 30 days after flowering,and the lignin content reached 373.49～595.28mg/g 51 days after flowering.During the development of the peel of the amygdala,the lignin content was positively correlated with the changes of cellulose content(0.27)and hemicellulose content(0.43),and the lignin content of the inner peel of thick-shelled almonds was greater than that of thin-shelled almonds.The activities of PAL,C4 H,4CL,CAD,POD and PPO enzymes decreased after decreasing or rising,and the activities of PAL,C4 H,POD and PPO were negatively correlated with lignin content,and the correlation coefficients were-0.45,-0.38,-0.43 and-0.52,respectively.Higher lignin-related enzyme activity can provide precursor substances for the accumulation of lignin. |
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