作 者 ：高晓旭 张志刚 段颖 董春娟 尚庆茂
期 刊 ：植物营养与肥料学报 2014年 20卷 5期 页码：1235-1243
Keywords:cucumber, tomato, hypocotyls,
摘 要 ：【目的】黄瓜和番茄是我国主栽蔬菜种类，育苗过程中容易遭遇高温、高湿、弱光等不良环境，导致幼苗下胚轴徒长，严重影响后期丰产性。在控制幼苗徒长的实际操作中，利用植物生长调节剂、机械刺激、补光、温度调节、水分控制等调控方法容易受到多种因素影响而效果不佳。本文研究高浓度营养液浓度对黄瓜和番茄幼苗下胚轴徒长的抑制作用，以期提出一种有效制御幼苗徒长的方法。【方法】试验以Hoagland标准营养液配方为基础浓度（设为1.0C），通过成比例增减大量元素组分用量而不改变微量元素组分用量，组成0.5C、2.5C、5.0C、7.5C、10.0C和12.5C 6个浓度。以0.5C为对照，在日光温室条件下分别对黄瓜和番茄幼苗进行灌施处理。待幼苗生长至子叶平展期时，测定黄瓜和番茄幼苗形态及生长指标，研究营养液浓度对幼苗下胚轴细胞长度、生长速率及内源激素含量的影响；随后对幼苗进行0.5C低浓度营养液的恢复生长处理，待幼苗生长至第一真叶平展期时，再次进行幼苗形态及生长指标的测定，从而确定高浓度营养液对黄瓜和番茄下胚轴徒长的抑制效果及机制，并确定最适合制御幼苗徒长的营养液浓度。【结果】6种浓度营养液对黄瓜和番茄幼苗下胚轴徒长的影响结果为： 1）高浓度营养液显著提高了基质EC值（r=0.99），黄瓜和番茄幼苗在子叶平展期其下胚轴生长受到明显抑制，下胚轴长度、绝对生长速率和含水量均呈下降趋势，下胚轴皮层薄壁细胞轴/径向生长也受到影响。与对照相比，10.0C营养液处理下黄瓜和番茄幼苗下胚轴皮层薄壁细胞缩短为49%和48%。2）随着营养液浓度的增加，黄瓜和番茄下胚轴内源激素含量发生显著变化，其中赤霉酸（GA3）、玉米素核苷（ZR）含量呈降低趋势，而脱落酸（ABA）含量呈升高趋势，且ABA含量与下胚轴长度呈极显著负相关关系（P＜0.01）。生长素（IAA）含量在不同浓度营养液处理下呈现区位性变化特征。3）在幼苗子叶平展期重新灌施0.5C浓度的营养液，对5.0C和7.5C处理下生长的幼苗均有恢复生长的作用，且幼苗株高/茎粗比明显优于对照和其它处理，该浓度可望有效避免幼苗徒长。【结论】高营浓度养液通过改变幼苗内源激素的动态平衡，特别是促进ABA的合成和积累，从而抑制幼苗下胚轴皮层细胞伸长生长，有效制御幼苗徒长。灌施高浓度营养液对黄瓜、番茄幼苗下胚轴伸长的抑制作用可以通过降低营养液浓度而得到解除，这种防治幼苗徒长的操作方法简便易行，具有潜在的应用前景，但在不同品种蔬菜幼苗生长过程中，最优化的营养液施用浓度及其影响机制尚需进一步研究分析。
Abstract:【Objectives】Cucumber (Cucumis sativus) and tomato (Lycopersicon esculentum) are main cultivated vegetable species in China. The seedling growth in breeding processes is vulnerable to disadvantageous environments, such as high temperature, high humidity and weak light, which lead to excessive hypocotyl stretch and reduced yield at later stage. Several methods such as plant growth regulators, mechanical stimulations, supplement of light, temperature modulation and water limitation are used to prevent excessive hypocotyl stretch, but the effects are always not satisfied by complicated influence factors. To develop an effective method for controlling hypocotyl stretch in cucumber and tomato seedlings, this paper focusses on the inhibition effect of high strength nutrient solution on hypocotyl stretch in cucumber and tomato seedlings.【Methods】The concentration of complete macroelement of 1.0 strength Hoagland nutrient solution is defined as fundamental formula (1.0C). Other nutrient solution concentration gradients involved in this experiment are 0.5, 2.5, 5.0, 7.5, 10.0 and 12.5C by adding macroelement compositions proportionally without changing the microelements compositions. 0.5C nutrient solution is set as control group, and others are treatment groups. After watering cucumber and tomato seedlings by different nutrient solutions in greenhouse conditions, the growth parameters are measured and the nutrient solution effects on hypocotyl cortical cell length, growth rate and phytohrmone levels are determined at cotyledon extending stage. Then seedlings are rewatered by 0.5C nutrient solution to restore the inhibition growth of hypocotyl stretch. The growth parameters are measured at the first true leaves extending stage. The effects and mechanism of high nutrient solution on inhibiting hypocotyl stretch are determined, and the optimal strength is acquired by appropriate effect on cucumber and tomato seedlings.【Results】The effects of six strength (0.5, 2.5, 5.0, 7.5, 10.0 and 12.5C) Hoagland’s nutrient solution on controlling excessive hypocotyl stretch are: (1) Electrical conductivity (EC) of substrate increases linearly (r=0.99) and growth of both cucumber and tomato are inhibited gradually from 0.5C to 12.5C nutrient solution. Compared with that under 0.5C nutrient solution, length of hypocotyl cortical cell decreases by 49% in cucumber and 48% in tomato under 10.0C nutrient solution. (2) Endogenous phytohormone homeostasis is disturbed by decreasing GA3 and ZR levels but increasing ABA levels, which significantly displays a negative correlation with hypocotyl length (P＜0.01). IAA levels shows differently tendency dependent on the concentration of nutrient solution. (3) The growth of hypocotyl stretch that has been inhibited by high strength of nutrient solution could be restored to different degree by rewatering 0.5C nutrient solution. Especially in 5.0C and 7.5C treatment, the ratio of plant height/stem diameter is better than that in other treatments, which is could be expected to effectively control excessive hypocotyl stretch. 【Conclusions】 High strength nutrient solution contributes to the inhibition effect on excessive hypocotyl stretch by changing endogenesis phytohormone homeostasis, apparently because of promoting more ABA synthesis and accumulation in hypocotyl cells, and shortening hypocotyl cortical cell length. The inhibition effect could be restored by decreasing the nutrient solution concentration. The method exhibits potential application prospect due to simple maneuverability and obvious effects, but the optimal strength and mechanism on different vegetable species still demand to be further studied and analysed.
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