Study On Tissue Anatomic Structure And Intracellular Lycopene Distribution In Different Ploidy Watermelon

The seedcoat and other tissues anatomic structure were studied by paraffin section method and scanning electron microscopy(SEM), and intracellular lycopene distribution of mescope samples was studied by transmission electron microscopy(TEM)in different ploidy watermelon, including diploid(2X),triploid(3X), and tetraploid(4X). The difference of tissue anatomic structure and intracellular lycopene distribution were compared in different ploidy watermelon. The result was as follow:1. The result showed that the seedcoat anatomic structure was different in different ploidy watermelons.1.1 In watermelon dry seed, the seedcoat, palisade tissue, hypodermis tissue and sclerenchyma tissue layers of triploid and tetraploid watermelon were thicker than the diploid watermelon. The hypodermis was comprised of small cells layer and large cells layer in triploid and tetraploid watermelon seedcoats, while the number of small cell was few in diploid watermelon. After soaking 12h in 55℃, seedcoat and other layers became thicker, the palisade tissue arranged pragmatically, the seedcoat and other layers of triploid and tetraploid watermelon were thicker than the diploid watermelon.1.2 The seedcoat surface structure was different in different ploidy watermelon cultivar xindon～18. The seedcoat surface structure of diploid watermelon is smooth without cracks, while the cracks were found on the surface of autotetraploid watermelon seedcoat.The cracks of autotetraploid watermelon were formed in two ways mainly, one way was that the hump part was formed by subcutaneous cells, and the hollow part was formed by the palisade tissue, following the subcutaneous tissue; the other way was that the palisade tissue was found on the surface of hump part, subcutaneous tissue was located in the hollow of seedcoat crack.2. Comprision of leaf anatomic structure in different ploidy i watermelon.2.1 The result showed that the leaf structures in different ploidy watermelons were different. At cotyledon period, the first euphylla period and the functional leaf period of watermelon, the leaf, palisade tissue and spongy tissue of triploid and tetraploid watermelon were thicker than diploid watermelon, CTR and the ratio of palisade tissue and spongy tissue of diploid watermelon leaf were higher than triploid and tetraploid watermelon, SR of triploid and tetraploid watermelon leaf was higher than diploid watermelon.2.2 The functional leaf anatomical structures in different parts were different in different ploidy watermelon. The leaf, palisade tissue and spongy tissue in the edge of functional leaf were thicker than the thickness in the middle of the leaf; CTR and the ratio of palisade tissue and spongy tissue in the edges were higher than in the middle, while SR was not different between different parts of functional leaf.3. The result showed that the rind structure was different in different ploidy watermelons. In mature watermelon,the rind,epidermis and exocarp layers of ployploidy watermelon were thicker than diploid watermelon, the stone cell was small and bulk in the diploid watermelon, the stone cell of the triploid watermelon was larger ,bulk and stratiform, and the tetraploid watermelon stone cell was larger and stratiform;a obvious transition from the small cell to the big cell was observed in the mesocarp layer of diploid watermelon, while this change was not obvious, and the cell in the mesocarp layer was large in the ployploidy watermelon. The difference of rind structure was observed in the different growth stage of watermelon fruit, no change was observed and the cell was uniform in the ovary wall after pollination 24h, the rind structure was formed and the stone cell was bulk, the size was triploid and tetraploid watermelon>triploid watermelon after pollination 20d, rind structure was formed fully in mature watermelon.4. The result showed that the form of chromoplast, riched in lycopene, was different in different ploidy watermelons. Chromoplasts in diploid watermelon were small and a number of chromoplasts composed the congeries together, few globular structure, ring-like structure and other structure were found; in triploid watermelon, chromoplasts had many forms, including globular structure, ring-like structure, thread-like structure and other structures, in particular,the thread-like structure was found only in triploid watermelon; the chromoplast in tetraploid watermelon was globular structure mainly, rich in stroma, few ring-like and others structure were found.