曼陀罗引种驯化前后光合特性的变化

[目的]研究曼陀罗引种驯化前后光合特性的变化。[方法]测定净光合速率、叶绿素、类胡萝卜素、可溶性糖和可溶性蛋白含量的变化。[结果]曼陀罗引种驯化前后光合日变化均为"双峰"型曲线,且存在光合"午休"现象。驯化后净光合速率、类胡萝卜素含量有所降低,可溶性糖含量、蛋白质含量有所提高,叶绿素含量提高极显著(P<0.01)。[结论]获得曼陀罗引种驯化前后光合特性的相关资料为更好地研究曼陀罗提供理论依据。     

紫花曼陀罗对粘虫和蚜虫的杀虫活性研究

研究了紫花曼陀罗不同部位不同极性溶剂粗提物对粘虫和蚜虫的杀虫活性。结果表明,紫花曼陀罗不同部位不同极性溶剂粗提物对粘虫的触杀作用以种子石油醚粗提物为最强,其次为种子乙酸乙酯粗提物,校正死亡率分别为65．88％和24．55％。不同部位甲醇粗提物对粘虫幼虫无拒食作用,对粘虫卵基本无杀伤作用。对棉蚜的触杀作用以种子乙酸乙酯粗提物为最强,其次为种子石油醚粗提物,校正死亡率分别为97．41％和94．18％;对桃蚜和麦长管蚜的触杀作用则以种子石油醚粗提物为最强,其次为种子乙酸乙酯粗提物,校正死亡率分别为60．99％和31．60％、34．88％和25．88％。     

曼陀罗浸提液对蔬菜种子萌发和幼苗生长的影响

[目的]研究曼陀罗对蔬菜的化感效应。[方法]用蒸馏水浸提曼陀罗茎段内的有效成分,以蒸馏水处理为对照,研究曼陀罗茎段浸提液对番茄、辣椒、苋菜、荆芥种子萌发和幼苗生长的影响。[结果]曼陀罗浸提液可降低4种蔬菜种子的发芽速率,降低番茄和辣椒种子的发芽率;0.2、0.4 g/ml曼陀罗浸提液处理后,番茄和辣椒种子的发芽率分别比对照降低了10.2%、9.4%和46.7%、34.7%。0.2g/ml曼陀罗浸提液抑制蔬菜根的生长,而对茎的生长却表现出促进作用;0.4 g/ml曼陀罗浸提液对蔬菜根的生长有很强的抑制作用,对茎段生长的抑制作用因物种不同而有很大差异。[结论]曼陀罗浸提液可抑制蔬菜种子萌发和幼苗根的生长。     

毛曼陀罗对粘虫和蚜虫的杀虫活性研究

研究了毛曼陀罗不同部位不同极性溶剂粗提物对粘虫和蚜虫的杀虫活性。结果表明,对粘虫的触杀作用以种子的石油醚粗提物为最强,其次为种子的乙酸乙酯粗提物,校正死亡率分别为50．00％和36．00％。不同部位甲醇粗提物对粘虫幼虫无拒食作用,对粘虫卵基本无杀伤作用。对棉蚜和麦长管蚜的触杀作用以种子的石油醚粗提物为最强,校正死亡率分别为68．54％和46．40％;其次为种子的乙酸乙酯粗提物,校正死亡率分别为62．84％和37．74％。对桃蚜的触杀作用以种子的乙酸乙酯粗提物为最强,校正死亡率为48．83％,其次为种子的石油醚粗提物,校正死亡率为29．36％。     

日光温室内大花曼陀罗单花开花习性研究

对日光温室内大花曼陀罗花器构造、单花的开花习性进行研究。试验结果表明,花梗和花冠的生长量受温度影响较大,花萼生长量受温度影响不大。此外,通过对花冠生长量的观察可知,3月的日光温室里大花曼陀罗单花现蕾期约5d,开花期约5d,衰落期约6d,单花花期约16d;4月的日光温室里大花曼陀罗单花现蕾期约5d,开花期约3d,衰落期约4d,单花花期约12d。     

低温胁迫响应的甜杨miR475靶基因的预测及表达

MicroRNAs（miRNAs）通过使靶mRNA降解或翻译参与生物体的转录后调控,并在植物对生物与非生物胁迫的应答过程中发挥重要作用。本研究基于相关数据库,利用生物信息学方法,通过搜索预测及实验验证得到甜杨（Populus suaveolens）低温响应miR475的12条潜在靶基因,并对其降解位点进行分析;同时,以低温（0℃）处理不同时间甜杨幼苗为试材,利用荧光定量PCR对miR475及其靶基因的表达谱进行检测分析,结果发现,随着低温诱导时间的延长,miR475表达量呈下调趋势,而其靶mRNA的表达量则呈现相反趋势,表明甜杨miR475可能以降解靶mRNA的方式在抵御低温中发挥作用。本文研究结果可为甜杨抗冻机制的后续深入研究提供科学依据。     

6种杀菌剂及其混配剂对香栓孔菌的室内毒力测定

在室内培养条件下,采用生长速率法测定了6种杀菌剂及其混配剂对香栓孔菌(Trametessuaveolens)的抑菌毒力。结果表明:不同杀菌剂对香栓孔菌的菌丝生长都表现出抑制作用,代森锰锌、退菌特、石硫合剂、可杀得、多菌灵和百菌清的EC50分别为16.91、26.83、118.49、365.38、412.29和1 556.76mg.L-1;退菌特和代森锰锌按1∶1、1∶3和3∶1比例混配都表现出一定的增效作用,其中按1∶3比例混配增效作用非常明显,共毒系数高达415.90,EC50仅为4.48mg.L-1。     

Characterization and Role of Glucose-6-phosphate Dehydrogenase of Populus suaveolens in Induction of Freezing Resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTTred) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTTred, indicating that the purified enzyme probably presented in cytosol of P suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P.suaveolens cuttings were also studied. The results show that G6PDH is characterized by Km value of 360/amol.L^-1 for G6P and 16μmol.L^-1 for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol‘L i except for NADPH and NADH)to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgC12, CaC12 and KC1 (all 1.0 mmol.L^-1) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl2 (1.0 mmol.L-1) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LTs0) of P. suaveolens cuttings during freezing acclimation at -20℃ were investigated. The results reveal that freezing acclimation decreases LTs0 of cuttings, and increases the activity of cytosolic G6PDH compared with control ones,while 2 d of de-acclimation at 25 ~C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT50. Furthermore,the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings.     

Validation of a weed:crop competition model

A model of crop:weed competition, based on parameters from the logistic biomass growth of both crop and weeds in monocultures, was validated under several sets of conditions. Model inputs were (i) dry matter per unit area at 50% of seedling emergence ( B_i ) for each species; (ii) maximum total biomass of each species in monocultures ( K ); (iii) intrinsic growth rate of each species in monocultures ( r ); (iv) the accumulated thermal time required for each species to reach 50% emergence; and (v) the total accumulated thermal time during the growing season considered in the simulation. The model adequately described the dynamics of the competition between species when the relative yield total of the mixture was close to one, i.e. the slope and intercept of the regression between observed and simulated values was not significantly different from one and zero respectively. Sensitivity analysis indicated that final crop biomass was particularly affected by changes in the relative growth rate of the species. The occurrence of a critical period for weed control was explored using the model. The simplicity of the model validated here would allow its use as a tool to predict the outcome of competition and species relative importance, particularly when parameters needed to run more complex models are not available.     

Weed Control of Four Higher Plant Species in Paddy Rice Fields in Southeast Asia

Four higher plants, namely glory bowers (Clerodendrum trichotomum L.), jimsonweed (Datura stramonium L.), beggarweed (Desmodium triflorum L.) and Chinaberry (Melia azedarach L.), with the strong allelopathic potential among 19 allelopathic species from Southeast Asia, were tested for their effects on weed emergence in paddy soil and field. In a greenhouse experiment, D. stramonium, D. triflorumand M. azedarach exhibited similar inhibitory magnitude at 1 t ha^?1 achieving more than 90 % weed control. C. trichotomum achieved about 70 % weed reduction at 2 t ha^?1. In paddy fields, D. triflorum was the most promising material for weed control and attained the highest rice yield among treatments, at the concentration of 2 t ha^?1, whereas the inhibition of D. stramonium and M. azedarach was weakened in the greenhouse. No injury of rice plants was observed. These plants might be used as natural herbicides to reduce the dependence on synthetic herbicides.