龙眼果皮发育解剖学观察

以储良龙眼品种为试材,观察了果皮的解剖结构发育特点。果皮发育早期(花后10d前),细胞体积小,排列紧密,细胞分裂活跃,外果皮有凸起的皱褶结构,有大量的表皮毛分化。果皮发育中期(花后10～52d),细胞体积变大,表皮毛开始脱落,外果皮逐渐平滑,中果皮处有石细胞群和海绵状组织的分化。果实发育后期(花后52d后,假种皮快速膨大阶段),有木栓形成层出现,形成周皮代替表皮起保护作用,随着果实生长,木栓层出现局部破裂。龙眼果皮可划分为外、中、内3层。中外果皮在发生次生木栓化前,由外表皮细胞及其附属物和角质层组成;在形成木栓形成层产生次生结构后,外果皮则由周皮组成。内果皮来源于子房内壁的几层细胞,由一层内表皮细胞和与之紧密相连的几层薄壁细胞组成。中果皮根据其组织特点可进一步分为上中果皮和下中果皮,上中果皮包括石细胞群、外层维管束和外果皮之内的薄壁细胞;下中果皮则主要包括海绵组织和其中的维管束。

An anatomical study on the pericarp development of longan

Fruits of longan(Dimocarpus longan Lour.) cultivar Chuliang was used for the study of the anatomic changes in pericarp during fruit development.At the early stage of fruit development(before 10 days after anthesis,DAA),the pericarp cells were small,dense and active in division.The pericarp grew unevenly with outgrowth of protuberances,resulting in a cristate surface.There was much epidermis hair differentiation.At the mid stage(between 10 and 52 DAA),cell size increased significantly,epidermis hairs shed and the protuberances gradually became flattened.Sclereid differentiation and spongy tissue formation also occurred at this stage.At the late stage after 52 DAA,when the aril underwent rapid expansion,secondary growth of the periderm occurred and replaced the epidermis as the outmost protecting layer.Localized phellem cracking was observed during fruit expansion.Longan pericarp structure could be divided into the exocarp,mesocarp and endocarp.Before the formation of periderm,the exocarp was composed of the epidermis and its attached structures such as epidermis hairs trichomes and cuticle.When the periderm was formed,the exocarp consisted of the cork,the cork cambium and phelloderm.The endocarp was composed of the inner epidermis and several layers of parenchymous cells,which were tightly connected with the inner epidermis.The mesocarp could be further divided into the upper mesocarp and the lower mesocarp.The upper mesocarp included the outer vascular bundles,sclerenchyma and the parenchyma below the exocarp,while the lower mesocarp was composed of mainly spongy tissue with scattered large vascular bundles.Differences in pericarp structure between longan and litchi were also discussed.