不同硬度西瓜果皮发育进程中硬度变化及解剖构造研究

Changes of hardness and anatomical structure of watermelon rind with differential firmness during ripening

为了揭示西瓜发育过程中与果皮硬度相关的细胞形态结构特征,以生育期相似但硬度差异显著的‘901’和‘BSH’为试验材料,采用质构仪穿刺法测定授粉后10、14、18、22、26、30 d不同发育阶段的果皮硬度和石蜡切片法观察比较果皮各发育阶段的细胞构造。结果表明:‘901’和‘BSH’果皮硬度在果实发育各阶段差异显著,‘901’果皮硬度在授粉后18 d达到峰值,此时石细胞团数量在整个发育时期最多,发育前期果皮硬度高于发育后期,表皮和外果皮细胞在整个发育时期排列整齐;‘BSH’果皮硬度在授粉后14 d达到最大,此时表皮细胞由不规则排列逐渐向规则排列分布,表皮和外果皮细胞逐渐增大,之后伴随果实发育果皮硬度逐渐降低。细胞学观察发现,‘901’外果皮和石细胞团结构层数较‘BSH’分别多1~2层,授粉后30 d,‘901’的中果皮细胞壁轮廓相对清晰,但开始出现溶解,‘BSH’的中果皮细胞壁部分溶解,液泡中出现絮状物。研究表明:西瓜果实耐裂性与果皮硬度相关联,西瓜果皮硬度与果皮细胞结构联系紧密,如外果皮和石细胞团结构层数、排列方式、石细胞团数量等,果皮硬度取决于果皮结构整体变化,并非单一因素变化。

This study aims to reveal the characteristics of morphology and structure of watermelon rind related to firmness during fruit development and ripening.'901'and'BSH'watermelon which had similar growth periods but significant differences were used as research materials to comparatively investigate the hardness of rind by texture analyzer and the mesocarp cell structure characteristics of fruits by paraffin section method at growth period of 10,14,18,22,26 and 30d after pollination.Rind hardness was significantly different in each stage of fruit development between'901'and'BSH'.The rind hardness of'901'reached its peak on the 18th day after pollination,and the number of stone cell clusters was the highest at this time in the whole development period.Rind hardness at early stage of development was higher than that of the late stage.The pericarp hardness of'BSH'reached its peak on the 14th day after pollination,and the epidermis cells gradually distributed from irregular arrangement to regular arrangement.Meanwhile,the epidermis and exocarp cells gradually increased,and then the rind hardness gradually decreased with fruit development.Cytological observation showed that the number of structural layers of exocarp and slith cells in'901'was 1-2 more than that in'BSH'.On the 30th day,the cell wall of'901'mesocarp was relatively clear and began to decomposed and the cell wall of'BSH'mesocarp partially dissolved and flocculation appeared in vacuoles.The crack resistance of watermelon fruit is related to the rind hardness,and the rind hardness is closely related to the peel cell structure,like the number of structural layers,arrangement,and number of stone cell clusters of exocarp etc.The rind hardness depends on the overall change of the peel structure,not a single factor change.