苜蓿根系生长性状及其与产草量关系的研究

对13个秋播苜蓿品种的根系生长性状进行调查研究,结合产草量分析表明:不同苜蓿品种间根系生长参数差异显著(P<0.05),其中Prime和WL323的根系植物量最高,大于32 g,WL323的侧根数最多,为17.8枝,综合评价以Prime、WL323、Super7和L90品种的根系生长性状最佳。在一年进行的3次刈割中,苜蓿自身根系的生长发育与第1次和第2次地上生长形成相互促进关系,而与第3次生长形成竞争关系,进入越冬时苜蓿根系的好坏制约着次年的产草量,特别是次年第3次的产草量。

根际细菌群落结构与装配对烟草根系生长性状的影响

植物根际微生物与植物生长密切相关,但根际微生物群落如何影响根系的发育情况仍研究甚少。本研究利用16S rRNA基因高通量测序技术检测了烟草的根际细菌群落,并探究了烟草根系不同发育情况与根际微生物群落差异的关联机制。结果表明:相比不发达根系(UDR),发达根系(WDR)的根际细菌物种的丰度和多样性均较高,Gallionella和Luteimona等属的丰度显著增加,而Edaphobaculum、PLTA13和Rhodobacter等属的丰度则显著降低(P<0.05);UDR的分子生态网络更加复杂,且物种间相互作用强,特别是合作行为,而WDR的网络关键节点数较多,其碳循环相关网络模块数与UDR相比增加;此外,WDR的根际细菌群落装配更趋向于发育聚集,且环境过滤在其中发挥了更重要的作用。总体上,本研究结果强调了根际微生物群落的结构组成、网络变化和群落装配在植物根系的生长过程中的重要作用,为植物根际微生物生态学研究提供了理论依据。

Growth Performance of Alfalfa(Medicago sativa)under Different Nitrogen Application Levels

Nitrogen addition is rather important to the growth of alfalfa. In this study, the effects of different nitrogen application levels on various growth characteristics of alfalfa were investigated. The results showed that nitrogen application exhibited no significant effects on plant height and stem diameter but posed significant effects on branch number of alfalfa. Branch number of alfalfa in each cutting raised with the increasing application level of nitrogen, with significant differences among different treatments （P〈0.05）; individual aboveground biomass increased with the increasing application level of nitrogen, but the increasing trend gradually tended to be steady from the first to the fourth cutting. Nitrogen application affected significantly （P〈0.05） individual aboveground biomass of alfalfa in the first, second and fourth cutting, but exhibited no significant effects on individual aboveground biomass of alfalfa in the third cutting. With the increase of nitrogen application level, total surface area, total volume, collar diameter and crossing number of alfalfa roots increased gradually, but total length, average diameter and furcating number of alfalfa roots increased first and then declined. Total length, average diameter and furcating number of alfalfa roots reached the maximum in N60 treatment.

Effects of Soil pH on Growth and Dry Matter Accumulation of Tobacco Plants

In order to clarify the relationships between soil pH and flue-cured tobacco growth and dry matter accumulation, effects of soil pH on root morphology and vigor, aboveground agronomic traits and dry matter accumulation of flue-cured tobacco were investigated by pot experiment. The results showed that on the whole, the intensity of soil pH on flue-cured tobacco growth and dry matter accumulation ranked as pH=6＇s 〉 pH=7＇s 〉 pH=5＇s 〉 pH=4＇s 〉 pH=8＇s. Acidic soil （pH=4） was not conducive to the early growth of tobacco plants, reduced root vigor and affected dry matter accumulation; and alkaline soil （pH=8） was not conducive to the growth of tobacco roots and shoot, reduced root vigor and affected dry matter accumulation. In conclusion, the suitable pH of soil for growth of flue-cured tobacco in Xiangxi is 5-7, but weakly acidic soil is the best.

Interactive effects of phosphorus deficiency and exogenous auxin on root morphological and physiological traits in white lupin (Lupinus albus L.)

White lupin （Lupinus albus） exhibits strong root morphological and physiological responses to phosphorus （P） deficiency and auxin treatments, but the interactive effects of P and auxin in regulating root morphological and physiological traits are not fully understood. This study aimed to assess white lupin root traits as influenced by P （0 or 250 ~tmol L-1） and auxin （10=8 mol L-1 NAA） in nutrient solution. Both P deficiency and auxin treatments significantly altered root morphological traits, as evi- denced by reduced taproot length, increased number and density of first-order lateral roots, and enhanced cluster-root for- marion. Changes in root physiological traits were also observed, i.e., increased proton, citrate, and acid phosphatase exudation. Exogenous auxin enhanced root responses and sensitivity to P deficiency. A significant interplay exists between P and auxin in the regulation of root morphological and physiological traits. Principal component analysis showed that P availability ex- plained 64.8% and auxin addition 21.3% of the total variation in root trait parameters, indicating that P availability is much more important than auxin in modifying root responses of white lupin. This suggests that white lupin can coordinate root mor- phological and physiological responses to enhance acquisition of P resources, with an optimal trade-off between root morpho- logical and physiological traits regulated by external stimuli such as P availability and auxin.