Study On Morphological Characteristics Of Watermelon And Selection Of Salt-Tolerance Of Induced Tetraploid Watermelon In Vitro

The effect of polyploidy on morphological characteristics of leaves, Histological anatomy of adventitious shoot formation from cotyledons and selection of salt-tolerance of tetraploid watermelon in vitro was investigated of different ploidy watermelon(diploid, triploid crossed with 4x×2x and autotetraploid induced by colchicine). In different field, the differentiation of different ploidy watermelon was discussed. The researches provided some useful information of selection of polyploid watermelon. The main results were as follows:1.At cotyledon period, upper epidermis is deeper than epidermis of leaf from Mimei and XQ;The compact extent on palisade tissue and spongy tissue is 2x﹥3x﹥4x; The ratio of palisade tissue and spongy tissue is 2 x﹥3x﹥4x;The protuberance of vein is 3x﹥4x﹥2x;The adaxial region of vein from 2x and 3x is concave,4x is flat,but the abaxial region of vein from 2x,3x and 4x is convex;The vein has only one large bundle.2.At the first euphylla period, upper epidermis is deeper than epidermis of leaf from Mimei and XQ; The compact extent on palisade tissue is M2x﹥M3x﹥M4x and XQ2x﹥XQ4x﹥XQ3x,respectively. The compact extent on spongy tissue is M3x﹥M2x﹥M4x,XQ4x﹥XQ3x﹥XQ2x,respectively.The change of the adaxial region of vein from Mimei is from round(2x) to flat(4x), The change of the abaxial region of vein from Mimei is from"∧"(2x) to round(4x).XQ is the inverse of Mimei;The vein of M2x have one large bundle and two small bundle,M3x have one large bundle and one small bundle,M4x has only one large bundle;XQ2x and XQ3x has one large bundle, XQ4x have one large bundle and one small bundle.3. CTR and SR of M4x and XQ4x are lowest and highest. The cold tolerance is 2x﹥3x﹥4x. The characteristics of cell structure in leaf tissue suggested the genetic differences of cold hardiness between Mimei and XQ appeared relatively stable and could be a cold tolerance parameter.4.The adventitious shoots of cotyledon from 91E7,XYXC and Zheng-3 is originated from deep tissue of cotyledon——around vascular tissue. 4x is ahead of 2x at shoot formation. At shoot formation, 4x and 2x are 4-8d and 8-10d, respectively.5.MS inducement medium is the best medium for selection of salt-tolerance of Mimei.The optimum range of salt concentration at separation of M2x and M4x is 0.7-0.85g/50ml culture medium.6.At NaCl concentration of 0-0.8g/50ml,the degree of salt injury connects with ploidy of Mimei. At NaCl concentration of 0.7-1.1g/50ml, the degree of salt injury is independent of ploidy of Mimei and XYXC.