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21.
Studies on the relationship between insect pests and their predators and parasites were conducted in the Syrian cotton agro-ecosystem
from 1980 up to 1983.Earias insulana (Boisduval) was found to be the most damaging pest, whileHeliothis armigera (Hübner) was not an annual returning problem. Among the entomophagous insects found, coccinellids were most numerous during
the months June and July and the hemipterous predators were more abundant during August and September.
When predator numbers were reduced with insecticide applications, a significant increase in the bollworm populations occurred,
resulting in significant reductions in seed cotton yields. Parasites were relatively not important for the control of lepidopterous
pests on cotton. Egg and larva populations ofE. insulana andH. armigera were parasitized byTrichogramma spp. andHabrobracon brevicornis Wesmael respectively. Populations ofBemisia tabaci (Gennadius) were heavily parasitized byEretmocerus mundus Mercet.
相似文献
22.
水分胁迫对棉花叶片中IAA从含量、IAA氧化酶和过氧化物酶活性的影响 总被引:2,自引:0,他引:2
整株干旱降低盐棉46号叶片中的IAA总量,叶龄愈小下降愈多。幼叶中IAA总量的下降主要是结合态IAA减少的结果。气干和-1.7MPa PEG溶液渗透胁迫处理也降低离体成熟叶片的IAA总量,其变化与叶片含水量呈直线相关(r=0.905)。整株干旱处理提高各叶片的过氧化物酶活性,叶龄愈小提高愈多,但IAA氧化酶活性无显著变化。离体和整株干旱时IAA总量的下降,可能是过氧化物酶活性增加所致。 相似文献
23.
华北棉区夏播棉田害虫发生特点分析 总被引:4,自引:1,他引:3
分析和比较了华北棉区夏季播种与春季播种的棉田主要害虫(棉铃虫与棉蚜)的发生特点,探讨了它们的管理对策。 相似文献
24.
Structural characterization of genes corresponding to cotton fiber mRNA, E6: reduced E6 protein in transgenic plants by antisense gene 总被引:13,自引:0,他引:13
Maliyakal E. John 《Plant molecular biology》1996,30(2):297-306
Two genes, each corresponding to fiber mRNA E6, were isolated from cotton cultivars Coker 312 (Gossypium hirsutum L.) and Sea Island (G. barbadense L.). E6 is one of the predominant fiber-specific mRNAs present during early fiber development. The distinguishing feature of the nucleotide-derived E6 protein is the presence of a motif where a dimer, Ser-Gly, is repeated several times. Two of the Sea Island genes contained a pentameric motif, Ser-Gly, while one of the Coker genes had one and the other had four motifs each. cDNA clones containing one or five Ser-Gly motifs were also identified. Thus, it appears that the strict conservation of this motif may not be critical to E6 protein function. Sequence characterizations of the genes and cDNAs showed that multiple members of the E6 family are transcribed in fiber and may result in proteins 238 to 246 amino acids long. The 3 ends of the genes and cDNAs showed considerable heterology among them. Transgenic plants containing antisense genes were generated to decipher E6 function. Transgenic cotton with reduced E6 protein levels in the range of 60 to 98% were identified. However, no discernible phenotypic changes in fiber development or properties were apparent. This result leads to the conclusion that E6 is not critical to the normal development or structural integrity of cotton fibers. 相似文献
25.
Mepiquat chloride (N, N-dimethylpiperidinium chloride), well known as PIX, is a potential systemic plant growth regulator. The effects of PIX on plant height, stem elongation, leaf area, net photosynthetic rates, chlorophyll content, sucrose and starch levels, and RuBP carboxylase activity in cotton (Gossypium hirsutum L. cv. DES 119) plants were measured. PIX was sprayed (0, 7.65, 15.3, 30.6 or 61.2 g active ingredient ha–1) on the plants at first square (25 days after emergence) and measurements were made at frequent intervals. Plant height was clearly reduced by PIX. The total length of vegetative branches and fruiting branches was 40% and 50% less than the control. Total leaf area in PIX treated plants was 16% less than the control. Net photosynthetic rates were 25% less in PIX-treated leaves. PIX treated leaves had more chlorophyll content. The activity of RuBP carboxylase was decreased in PIX treated plants. Starch accumulation was noticed in PIX treated leaves while sucrose content was not changed. The data reported here suggest that reduced growth responses induced by PIX results in partial loss of photosynthetic capacity in cotton at least up to 20 days after application of the growth regulator. 相似文献
26.
The Biology of the Tospoviruses 总被引:1,自引:0,他引:1
The tospoviruses are a diverse, cosmopolitan and economically important genus of plant viruses. In the recent past, interest in the tospoviruses has been rekindled with the resurgence and expansion of tomato spotted wilt virus and the appearance of new tospoviruses, including impatiens necrotic spot. This renewed interest in the tospoviruses, accompanied with the many recent advances in plant virology techniques, particularly those utilising molecular biology, have resulted in a rapid growth of our understanding of these viruses. This paper provides a review of the tospoviruses, encompassing all the major aspects of their biology, including the recent changes in the classification of the genus and current knowledge on molecular biology, vector relations, control and diagnosis. 相似文献
27.
新的生物杀虫剂螨虫素对棉花、蔬菜害虫的毒力评价及应用技术研究 总被引:2,自引:0,他引:2
本文通过生物杀虫剂螨虫素对棉花、蔬菜害虫的毒力评价及田间应用研究表明,它对棉朱砂叶螨和菜青虫两种害虫杀伤力最强,其中LC90分别为0.078ppm和0.013ppm。兼有胃毒、触杀作用,残效期较长,分别达13天和9天。田间小区试验认为防治菜青虫和茄朱砂叶螨以2ppm浓度为宜。防治适期为卵孵化初期或低龄幼(若)虫(螨)期,其防效能达90%以上。该药特点用药量低、效果好、无公害、值得推广。 相似文献
28.
Selection for higher yields and heat resistance in Pima cotton has caused genetically determined changes in stomatal conductances 总被引:1,自引:0,他引:1
Gas exchange analysis was used to characterize photosynthetic and stomatal responses to key environmental stimuli in five commercial lines of Pima cotton ( Gossypium barbadense L.) which represent a gradient of selection for higher yields and heat resistance, and a primitive, uncultivated G. barbadense. At constant light and vapor pressure deficit, stomatal conductance increased linearly with air temperature in the 23 to 36$C range in all five commercial lines, and conductance at each temperature increased as a function of selection. In contrast, photosynthetic rates had a low sensitivity to temperature in the 23 to 36$C range, particularly in the advanced lines. In a segregating F2 population from a cross between the advanced line, Pima S-6, and the primitive cotton, B368, the slope of the stomatal response to temperature in each F2 plant was positively correlated with the stomatal conductance measured at 40$C. An analysis of the frequency distribution of stomatal conductance in F1 and F2 progeny of the cross showed that the differences in stomatal conductance between lines were genetically determined. These data indicate that selection for higher yield and heat resistance in Pima cotton has caused genetically determined changes in stomatal properties. Characterization of the relationship between the altered stomatal properties and the attained increases in heat resistance and yields could make it possible to use these physiological traits as selection criteria in future breeding programs. 相似文献
29.
棉田生态系统能流经济阈值的初步研究 总被引:5,自引:0,他引:5
系统能流经济阈值(EET)为本项研究提出的新概念。它是指系统的初级生产者-作物向其它亚系统输出能量的允许临界值,由此产生的期望收益最大,系统能流经济阈值是一条仅与作用现丰量相关的动态曲线,与其他亚系统无直接关系,本文以末施药棉田为系统,提出能流经济阈值的研究方法为:建立能流动态模型;确定害虫防治代价,计算期望产出,运用计算机仿真语言对作物的能流输出参数进行优化并建立系统能流经济阈值模型。 相似文献
30.