【作者】 唐海明；

【导师】 陈金湘；

【作者基本信息】 湖南农业大学 ， 作物学， 2008， 博士

【摘要】 我国在棉花育苗上已经发展了营养钵育苗、芦管育苗、无土育苗和穴盘育苗等技术,黄河流域和西北内陆棉区以种子直播为主,长江流域主要种植杂交棉,而采用育苗移栽技术。目前,在棉花育苗移栽上存在出苗、成苗率低,劳动强度大等问题。最近,湖南农业大学棉花研究所在国内外棉花、烟草、蔬菜和花卉等育苗方法的基础上创建了一项新的棉花育苗方法——棉花营养液漂浮育苗技术。该育苗技术通过采用多孔聚乙烯泡沫育苗盘为载体,以混配基质为支撑,以营养液水体为苗床进行漂浮育苗,能使优良棉种的出苗率超过95%,成苗率达到90%以上,与其它育苗方式相比具有省工、省力、节本和增产等优点。自2005年起,棉花营养液漂浮育苗技术已在湖南、湖北、江西和安徽等省进行了大面积的推广应用。本研究以农杂66和湘杂棉8号为试验材料,从形态、细胞学和生理生化水平等方面,对营养液漂浮育苗过程中棉花幼苗根系的形态建成及其适应机制进行详细的研究,以明确棉花幼苗在营养液中漂浮生长发育动态以及对水生环境的适应性过程,为该棉花育苗技术的应用提供坚实的理论基础。1营养液漂浮育苗棉苗根系形态和生理生化特性（1）在营养液漂浮育苗中,采用催芽播种方式,育苗盘中以棉花种子胚根朝下倾斜播放为最佳方式,根系穿孔率达97.0%,戴壳率仅为3.0%。当播种深度为1.0～2.0 cm时,种子所处的基质层面含水量为68%～85%,不仅有利于根系的形成和生长发育,而且有利于侧根的发生及根系形态建成。（2）营养液漂浮育苗棉苗根系分为两种类型:旱生根系和水生根系。旱生根系呈弹簧状,而水生根系白嫩,根尖肥大,柔软并且富有弹性。自棉花幼苗1叶1心至5叶1心,营养液漂浮生长的棉苗根系发达,根系鲜重、干重、根长、根体积和根冠比与营养钵育苗棉苗（对照）的差异均达到显著水平;根系密度增大,一级侧根和二级侧根明显多于对照,从而增加了营养液漂浮生长的棉苗根系总吸收面积和活跃吸收面积。（3）营养液漂浮育苗棉苗旱生根系的表皮细胞完整,表皮细胞体积小,排列紧密、整齐紧凑,细胞壁加厚程度大,皮层薄壁细胞形成了部分通气组织。水生根系的表皮细胞排列松散,皮层薄壁细胞体积较大,大部分皮层薄壁细胞融合形成发达的通气组织,有利于氧气的传送。因此,根系通气组织的形成是棉苗适应水生环境主要特征。与营养钵中生长的棉花幼苗相比,营养液中漂浮生长的幼苗根系皮层厚度明显变薄,而根系中柱半径、导管直径均增大,因此增强了根系对水分的运输能力。（4）对营养液漂浮育苗棉苗根系的生理生化特性研究发现,营养液漂浮育苗增加了幼苗根系的TTC还原强度。在农杂66幼苗从1叶1心至5叶1心5个生长时期中,根系还原强度分别比对照提高12.4%、11.4%、14.2%、22.9%和10.5%。湘杂棉8号幼苗从1叶1心至5叶1心5个生长时期,棉苗根系还原强度分别比对照提高10.3%、12.4%、14.8%、21.0%和8.8%。营养液漂浮育苗棉苗根系中SOD、POD和CAT保护酶活性均有不同程度地提高,而O₂^-和MDA含量呈下降的变化趋势,表明营养液漂浮育苗能增加棉苗根系保护酶活性,降低膜脂过氧化作用,从而起到保护膜结构的完整性和提高棉苗抗逆性的作用。（5）从1叶1心至5叶1心,农杂66和湘杂棉8号两个品种的营养液漂浮育苗棉苗根系中纤维素酶活性均比营养钵中生长的幼苗高,并在2叶1心时期达到最大值。两个品种营养液漂浮育苗棉苗旱生根系的纤维素酶活性分别为0.548μg/（g·min）和0.668μg/（g·min）,水生根系的纤维素酶活性分别为0.551μg/（g·min）和0.702μg/（g·min）。另外,自1叶1心至5叶1心,营养液漂浮育苗棉苗根系内源乙烯含量及生成速率明显高于对照。在淹水的条件下,促进了营养液漂浮育苗棉苗根系纤维素酶活性的提高,加速了皮层细胞的融合,而内源乙烯含量的增加促进了根系皮层细胞死亡解体,因而有利于根系通气组织的形成。（6）自1叶1心至5叶1心,营养液漂浮育苗棉苗根系的LDH（乳酸脱氢酶）和ADH（乙醇脱氢酶）活性均高于对照。两种不同类型根系中,旱生根系ADH活性高于水生根系;水生根系LDH酶活性高于旱生根系。棉苗根系中ADH、LDH活性的提高,增强有氧呼吸酶活性,并避免乳酸和乙醛大量积累对棉苗的伤害,从而缓解了低氧胁迫对棉苗的伤害,增强了营养液中漂浮生长幼苗耐低氧的能力。2营养液漂浮育苗棉苗茎叶生理生化特性（1）与营养钵育苗方法相比,在棉花幼苗自1叶1心至5叶1心生长发育过程中,营养液漂浮育苗法提高了幼苗叶片的叶绿素、可溶性蛋白质和可溶性糖含量。（2）在棉花幼苗从1叶1心至5叶1心5个生长时期中,营养液漂浮育苗棉苗叶片SOD、POD和CAT保护酶活性均有不同程度地提高,O₂^-和MDA含量呈下降趋势,表明营养液漂浮育苗能增加棉苗叶片保护酶的活性,降低膜脂过氧化作用,从而起到保护膜结构的完整性和提高棉苗抗逆性的作用。更多还原

【Abstract】 At present,a lot of cotton seedling cultivation technologies such as nutritive bowls nursing seedling（NBNS）,nursing cotton seedling with reed-tube,soilless seedling,plug seedling and so on,have been developed in China cotton production. Cotton seed was directly sown into soil in Yellow River Basin and Northwestern region in China,and the seedling transplanting technique is adopted in Yangtze River Basin where hybrid cotton is mainly planted.The seedling transplanting technique is mainly applied with some shortcomings such as low seedling emergence and stand rate and labor-consuming.Based on the present seedling nursery methods of cotton, vegetable,and tobacco in domestic and abroad,a new cotton seedling nursery technology,the floating nursing seedling in nutrient water-bed（FNSNWB） is developed by Cotton Research Institute of Hunan Agricultural University.Cotton seeds are sown in patented mix media carried in a porous polyethylene plate which is floated on nourishing water according to the technology of FNSNWB.The seedling emergence of cotton is above 95%and stand rate above 90%by the new method. Compared with other seedling nursing technologies,the FNSNWB has many advantages with low cost,high efficiency,labor-saving and yield increasing.The FNSNWB has achieved greatly and was applied so far in Hunan,Hubei,Jiangxi and Anhui provinces since 2005.In order to explore the morphological characteristics and the physiological-ecological adaptation mechanisms of roots of cotton seedling nursed with the method of FNSNWB,Nongza 66 and Xiangzamian 8 were used as the materials to study the growth and development of roots and shoots and their adaptation to water environment at morphological,cytological and physiological-biochemical levels in the present paper. 1 The morphology and physiological-biochemical characteristics of cotton seedling roots of FNSNWB（1） It is found that the best sowing pattern was to lay cotton seed radicles slope with underneath,which the root through porous polyethylene hole rate reach 97.0% and the rate of seedling with seed coat was 3.0%.The sowing depth from 1.0 to 2.0 cm,where the moisture of medium around the seedlings was about 68-85%,was beneficial not only to the root system’s formation and growth but also to the lateral roots occurrence.（2） According to the results of research on the morphological characteristics,the roots of FNSNWB can be divided into two different types.The roots growing in the medium were called drought roots with spring shape,and the roots growing in the nutrient water were called hydrophilic ones.The hydrophilic roots are white and tender with fat,soft and flexible tips.From one leaf to five leaves stages,the fresh and dry weight of root,ratio of root to shoot,root volume,root length and root density of seedlings with FNSNWB were significantly more than that of the seedlings with NBNS.Meanwhile,the lateral roots of FNSNWB grew more,which enhance the total root surface area and active absorption area of root.（3） The drought roots have a lot of characteristics with closely arranged and neatly compacted epidermis cell,thickened cell wall and the cortical cell forming some parenchyma.The hydrophilic roots also have a lot of remarkable characteristics with arranged loosely and disorderly epidermis cell,argumented cortical cell.The cortical cells merged into a lot of parenchyma for the transportation of oxygen. Therefore,the formation of parenchyma in root system was the main trait of cotton seedlings that adapted to aquatic environment.The root cortex thickness of cotton seedlings of FNSNWB became thinner,and the root stele radius and root diameter vessel was increased comparing with NBNS,which improved the ability of water trasportion of root system.（4） Compared with the roots of seedlings with NBNS,the TTC reductive intensity in the ones of seedlings with FNSNWB increased by 12.4%,11.4%,14.2%, 22.9%and 10.5%from one leaf to five leaves stages using Nongza 66 as experimental material.The TTC reductive intensity increased by 10.3%,12.4%,14.8%,21.0%and 8.8%from one leaf to five leaves stages using the Xiangzamian 8 as experimental material.During the stage of seedling,the activities of superoxide dismutase（SOD）, peroxides（POD） and catalase（CAT） of cotton seedlings roots fostered by FNSNWB were higher than those of the NBNS.Meanwhile,the accumulation of O₂^- and MDA content of cotton seedlings roots decreased.Our results showed that the FNSNWB can increase the activities of SOD,POD and CAT,and decrease the function of membrane lipid peroxidation of cotton roots.Therefore,FNSNWB can protect the intactness of membrane structure and increase the stress resistance of cotton seedlings.（5） From one leaf to five leaves stages the cellulose activities of cotton seedlings roots of FNSNMB were stronger than that of NBNS.The cellulose activities reach the peak at two leaves stage,when the cellulose activities of the drought roots of the two varieties（Nongza 66 and Xiangzamian 8） reach 0.548μg/（g·min） and 0.668μg/（g·min）, respectively,and the cellulose activities of hydrophilic roots reach 0.551μg/（g·min） and 0.702μg/（g·min）,respectively.Under the water cultural condition,the cellulose activities of cotton seedlings roots were stimulated and led to accelerate cell fusion. Moreover,compared with NBNS,the ethylene content and its synthesize rate of cotton seedlings roots of FNSNWB from one leaf to five leaves stages were increased, which accelerated the death of the cortical cells and the aerenchyma formation in cortical cell.（6） From one leaf to five leaves stages,the activities of LDH and ADH in roots fostered by FNSNWB were stronger that that of NBNS.For the two different types of roots,the ADH activities of the drought roots were higher than that of the hydrophilic roots.The LDH activities of the hydrophilic roots were higher than that of the drought roots.Therefore,FNSNMB can increase LDH and ADH activities in a wide range in roots and enhance the respiration enzyme activities,which avoid the damage of massive accumulations of lactate and acetaldehyde and thypoxia resistance.Thus,the hypoxia resistance of cotton seedlings fostered by FNSNWB was enhanced. 2 The physiological and biochemical characteristics of cotton seedling shoots of FNSNWB（1） The leaf chlorophyll,soluble protein and sugar contents in cotton seedling of FNSNWB from one leaf to five leaves stages were significantly different from that of seedling of NBNS.（2） From one leaf to five leaves stages,the activities of SOD,POD and CAT of cotton seedlings leaves fostered by FNSNWB were higher than those of the NBNS. Meanwhile,the accumulation of O₂^- content and MDA content of cotton seedlings leaves decreased.Our results showed that the FNSNWB can increase the activities of SOD,POD and CAT and decrease function of membrane lipid peroxidation of cotton leaves.Therefore,FNSNWB may protect the intactness of membrane structure and increase the stress resistance of cotton seedlings.更多还原