【作者】 陈钢；

【导师】 吴礼树；

【作者基本信息】 华中农业大学 ， 植物营养学， 2008， 博士

【摘要】 西瓜（Citrulluis vulgaris Schrad）已成为我国主要经济作物之一,尤其是近十年来发展迅速。随着现代农业技术的发展,西瓜新品种层出不穷,但往往只注重从某一个性状或者一个方面去改良西瓜,一旦改变其生存的环境,产量和品质会随之变化,西瓜良种在种植的过程中会遇到一些自然的或者人为因素带来的障碍,而使产量下降和品质变劣。长江中下游地区,每年早春都会遭遇频繁的“倒春寒”,严重影响西瓜幼苗生长,对产量和品质的形成带来不利影响。虽然西瓜的抗寒性和品质主要由遗传基因控制,但后期种植过程中的综合管理非常重要,而养分是其中的首要因素。本课题主要研究磷对西瓜生长、产量、品质及磷硼配合对其幼苗抗冷性的影响,得出如下结论:1营养液培养试验表明:硼磷及其配合不同程度地促进西瓜幼苗生长、提高幼苗对寒冷的抵抗能力,适量增施磷硼是西瓜育苗中的重要环节。1.1缺磷使西瓜幼苗叶面积减小,叶片数减少,显著影响叶片正常生长和发育,而缺硼的影响相对较小。适量硼、磷配合能促进西瓜幼苗正常生长发育,降低冷害指数,提高西瓜幼苗的耐冷性。1.2磷、硼尤其是两者配合能促进氮磷钾自西瓜根部向地上部运输,能促进根部对氮的吸收和向地上部的运输和积累,从而促进植株的生长。缺磷时,硼更加抑制西瓜对磷的吸收,并导致磷含量下降;而磷适量时,硼促进西瓜对磷的吸收。缺硼条件下,磷抑制西瓜对硼的吸收而激化西瓜硼缺乏。硼抑制常温下西瓜幼苗吸收镁,却促进低温下西瓜吸收镁。低温下缺硼对西瓜吸收钙有抑制趋势。1.3低温下,磷硼尤其是其配合能通过提高可溶性糖含量;无论常温和低温条件,施入磷硼均能降低MDA含量和电导率,低温下表现显著,尤其是磷硼配合处理,下降幅度最大。说明低温胁迫下磷硼配施能减少电解质的渗漏和维持细胞水势的稳定,极大缓解西瓜幼苗细胞膜所受的伤害。可溶性糖和电导率可作为较为快速鉴定西瓜幼苗耐冷性的指标。2沙培试验表明:磷不同用量不同程度影响西瓜生长发育及各种养分的吸收,最终影响产量和品质。2.1过多的磷通过抑制作物叶片对铁元素的吸收和利用而降低叶绿素的含量,因此过量磷的使用下,叶片颜色暗绿。不能仅仅从“稀释效应”来解释高磷条件下叶绿素含量下降的问题。2.2开花期是营养生长与生殖生长共进阶段,此时对磷的需求相对整个生育期而言增多,此时需要足够的磷素,磷供应不充足,会影响核酸的合成,从而影响植株的生长和发育,西瓜开花期如果磷的供应不充足,将会减少植物体内核酸的合成,从而影响或抑制作物的生长发育和推迟生育期。过量的磷的用量会降低茎杆的纤维素含量,磷的合理施用量及与氮钾等养分的适宜比例对纤维素的形成很重要。2.3西瓜生长的前期,即以营养生长为主的苗期和伸蔓期,氮、磷、钾的含量均随磷浓度的增加而增加,此时氮磷、磷、钾表现互相促进,而转入营养生长与生殖生长共进,以及以生殖生长为主的开花期、座果期和成熟期,叶片中氮、磷、钾含量变化趋势发生了变化:氮含量随着磷浓度的增加,呈现下降趋势,而磷和钾有随磷浓度增加,逐渐上升的趋势,说明氮对西瓜前期的重要,和开花期磷的重要性以及后期对钾的需要逐渐增多。西瓜的一生中需钾最多,氮次之,磷最少。磷抑制西瓜地上部对钙镁铁铜锌的吸收,但促进对硼钼锰的吸收。但对于养分是促进或抑制也受到作物、作物不同的生长阶段以及作物的部位的影响。2.4缺磷导致了西瓜产量的下降;同时西瓜子粒增多;过量的磷抑制作物对氮的吸收和运转,使西瓜产量下降。同时导致西瓜果肉部分白筋比例明显上升。2.5苹果酸和柠檬酸不是影响西瓜有效酸的主要因素。适宜磷用量时,苹果酸和与番茄红素含量最高,说明养分间的比例的平衡对二者的合成或分解产生很大的影响,而并非磷的绝对用量。磷对糖的影响更大,而对酸度影响很小。磷缺乏使西瓜果肉中可溶性糖的分布向中部集中,极不均匀,影响西瓜的整体风味。影响西瓜的甜度因素,是蔗糖、果糖、葡萄糖三种糖共同的作用,而至于以哪种水溶性糖为主,可能与作物的品种,生育期以及施肥等综合因素有关。3田间试验表明:在磷适量的土壤上增施磷肥,能增加单位西瓜个数和重量,提高产量,磷对增加西瓜个数更为突出。在一定的范围内,随着P₂O₅用量的上升,西瓜产量增加,但当每公顷P₂O₅用量达到300 Kg以后,西瓜产量开始呈下降趋势。可溶性糖变化趋势与产量基本一致。在一定的范围内,增加磷肥有提高维生素C含量的趋势,超过了一定的范围,其含量下降;磷肥对硝酸盐的含量也有很大的影响,总趋势是,增施磷肥各处理的硝酸盐含量比对照显著上升。综合产量和品质看,P₃处理即150kg/hm²为较合适的磷用量。产量效应函数:Y=60.2586+0.7084x-0.0017x²（r=0.9533*）。更多还原

【Abstract】 The experiment study obstacles of chilling injury on watermelon seedling stage, impact of lack and excessive of nutrients on watermelon growth process,and the most appropriate local watermelon nutrient usage and management,as well as the growth and development of physiological,the main results were shown as followed:1 Nutrient solution experiments results were shown:phosphorus and boron promote watermelon seedling growth,improve seedling resistance to the cold,so appropriate dosage of phosphorus and boron is an important measure on watermelon seedlings:1.1 phosphorus deficiency lead to reduce watermelon leaf area,and slow growth rate of leaves,and its less affected by boron deficiency,but adding suitable boron with phosphorus can promote watermelon seedling normal growth and development, reduce cold injury index,raising the watermelon seedling cold tolerance.1.2 Phosphorus,boron and its cooperation can promote transportation and absorbtation of nitrogen,phosphorus and potassium from roots to ground,especially phosphorus with boron is more prominent,which can promote the roots’ absorption of nitrogen,and nitrogen’s transportation and accumulation to ground,thereby promoting the growth of plants.Boron deficiency more inhibited the crops to absorption of phosphorus,caused the decline in phosphorus content,and boron can promote the absorption of phosphorus under appropriate amount of phosphorus;also boron deficiency,phosphorus inhibit crops to uptake boron,and more sharpened the lack of boron,at room temperature,boron inhibits the absorption of magnesium in watermelon seedlings,and low temperature increase the absorption of magnesium. boron deficiency under low temperature conditions,normal phosphate level has a trend to suppress calcium absorption.1.3 Low temperature,phosphorus with boron can improve soluble sugar content and reduce the content of MDA and conductivity,this means that under low temperature stress,phosphorus combined application of boron can reduce electrolyte leakage of water potential and maintain the stability and greatly ease watermelon seedling membrane for the injuries suffered.Soluble sugar and conductivity can be used as a more rapid identification of watermelon seedling cold tolerance indicators.2 The sand experiments results were shown:the amount of phosphorus has different impacts on watermel growth and nutrient absorption,and ultimately affect the yield and quality:2.1 Excessive phosphorus inhibits leaves’ absorption and utilization to iron,so decreasing chlorophyll content;the use of excessive phosphorus lead to light green leaf color,the actual observation of this is the case.therefore,"dilution effect" can not fully explain the high phosphorus led to the phenomenon of lower chlorophyll content.2.2 If the supply of phosphorus is not sufficient on watermelon flowering period, which will reduce nucleic acid synthesis,thus affecting or inhibiting the growth of crops and delaying childbearing period,also excessive amount of phosphorus will low down the stem cellulose content.2.3 Growth of watermelon early,nitrogen,phosphorus,and potassium content increases with phosphorus level,and bloom,fruit and maturity period,leaf nitrogen content shows a downward trend,phosphorus inhibits part of the ground absorption of Ca,Mg,Cu,Zn and Fe,but promotes absorption of B,Mo and Mn.but the promotion or inhibition of nutrients may be effected by crop varieties,crop growth stages and different parts of the crops.2.4 phosphorus deficiency led to a decline in yield of watermelon,and increasing of watermelon seed;excessive phosphorus also results yield decline from inhibiting crop on nitrogen uptake and functioning,and at the same time it leads to some increases in the percentage of gluten.2.5 Malic acid and citric acid are not the main factors in affecting effective acid of watermelon,malic acid and lycopene have the highest content under appropriate amount of phosphorus,it shows nutrient balance is important to synthetic or decomposition of the two components,and not the absolute amount of phosphorus. Phosphorus has greater impact on the sugar,and little effect on the acidity. phosphorus deficiency leads to soluble sugar uneven distribution in the watermelon flesh,which through soluble sugar move to central,so the overall impact on watermelon flavor.The sucrose,fructose,glucose sugar are common affecting factors in sweetness of watermelon,as which soluble sugar is major affecting factors,that may be associate with crop species,growth stage,as well as the comprehensive factors such as fertilizer.3 The field experiment results were shown:phosphorus can increase the number and weight of watermelons,and raise yield of watermelon;effect of phosphorus is better on increasing number of watermelons,for the yield,with the increased amount of phosphorus,watermelon production added,but to a certain volume,a low trend started,content of soluble sugar have same trend with yield basically,in certain areas, vitamin C content can be increased with phosphate added,phosphate also have a great impact on content of nitrat,the trend is,the nitrate content of the treatments that used phosphate is significantly over CK.In the words,P₃（150 kg/hm²） is more appropriate to add yield and improve quality.更多还原