棉株根系伤流中的细胞分裂素类物质

棉株根系伤流有明显昼夜节奏,白天多,夜晚较少。白天中又以上午9～12时的伤流量为最高。伤流中CTK量及其浓度也以白天为高。在切除地上部4天以后,从蕾期和铃期棉株已不再能收集到伤流液,但盛花期棉株在切除地上部6天以后,仍产生了相当多的伤流,其中仍含有丰富的CTK类物质。盛花期棉株根系伤流量及其中CTK水平高于铃期棉株,提示铃期棉株根系活力已开始趋向衰老。根据Sephadex LH-20柱层析及高效液相层析鉴定出棉株根系伤流中的CTK类物质有Z,ZR,和IPA。     

Behavioural response of spider mites (Tetranychus urticae) to induced resistance of cotton plants

ABSTRACT.

• 1 Spider mites (Tetranychus urticae Koch) given a choice between a cotton plant previously damaged by mites and an undamaged control preferentially moved to the control plant.
• 2 This host-choice behaviour was seen in adult female mites but not in immatures.
• 3 Adult females were not found to be significantly more fecund on control plants than on previously damaged plants, but the duration of this choice experiment precluded full assessment of effects on fecundity.
• 4 Mites responded very quickly, choosing previously undamaged plants without contacting or feeding on the test plants. This suggests that an olfactory response to a chemical substance(s) is involved.

     

Influence of Environmental Factors on the Hatch and Survival of Meloidogyne incognita

The influence of soil temperature and moisture on Meloidogyne incognita (Kofoid and White) Chitwood was examined in relation to hatching and survival of second-stage juveniles (J2). Nematodes were cultured on cotton (Gossypium hirsutum L. cv. Acala SJ2) under field conditions to provide populations similar to those found in the field in late autumn. Egg masses were placed in a temperature range (9-12 C and 21 C), and hatch was measured over a period equivalent to 20 degree days > 10 C (DD10). Hatch occurred below the reported 18 C activity threshold, was restricted below 12 C, and was inhibited below 10 C. Soil moisture influence on hatch was measured by placing egg masses in Hesperia sandy loam and subjecting them to suction pressures ranging from -1.1 bars to -4 .5 bars. Suction potentials of less than -2 bars reduced hatch and less than -3 bars inhibited hatch. J2 were placed in sandy loam soil with soil moisture near field capacity, and their motility was measured over a period of 500 DD10. In the absence of a host, more than 90% of J2 became nonmotile over this period.     

The role of predators and parasites in controlling populations ofEarias insulana,heliothis armigera andBemisia tabaci on cotton in the Syrian Arab Republic

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.      

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

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。     

华北棉区夏播棉田害虫发生特点分析

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。     

利用TMV—U1作为载体表达鼠肝炎病毒S糖蛋白片段

为了验证转基因烟草中表达的外壳蛋白（ＣＰ）能够重新包被侵入的烟草花叶病毒（ＴＭＶ）的假设,利用抗原表位标记的方法观察ＣＰ亚单位在病毒５′端的交换。通过ＰＣＲ 方法将来源于鼠肝炎病毒（ＭＨＶ） Ｓ蛋白的两个小肽段（１１ ａ．ａ．和１５ ａ．ａ．）的ＤＮＡ序列分别插入ＴＭＶ－Ｕ１ ＣＰ基因邻近３′端的两个位点,并构建了带有外源序列的ＴＭＶ 侵染克隆Ｖ９ （１１ ａ．ａ．）和Ｅ１５ （１５ ａ．ａ．）。通过体外转录反应,得到Ｖ９ ＲＮＡ 及Ｅ１５ ＲＮＡ。突变病毒ＲＮＡ 侵染烟草（Ｎｉｃｏｔｉａｎａ ｔａｂａｃｕｍ ）后表现不同特性。Ｖ９ 和Ｅ１５ 侵染ＸａｎｔｈｉＮＮ烟草后同野生型ＴＭＶ一样产生枯斑。但是,当它们侵染Ｘａｎｔｈｉｎｎ 烟草时,Ｖ９ 产生同侵染ＸａｎｔｈｉＮＮ 烟草相同的枯斑,而Ｅ１５的特性同ＴＭＶ－Ｕ１几乎完全相同,能对Ｘａｎｔｈｉｎｎ 烟草进行系统侵染并在叶片中聚集大量的带有外源片段的外壳蛋白,而且病毒的结构极其稳定。Ｖ９ 和Ｅ１５ 特性的差异可能是由于外源片段在外壳蛋白中存在位置的不同影响了外壳蛋白的结构所致     

Structural characterization of genes corresponding to cotton fiber mRNA, E6: reduced E6 protein in transgenic plants by antisense gene

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.