EFFECT OF 2,4-DICHLOROPHENOXYACETIC ACID ON THE FINE STRUCTURE OF CHLORELLA PYRENOIDOSA CHICK1

Chlorella pyrenoidosa Chick cells grown in liquid culture containing 5 × 10^?3M sodium 2,4-dichloro-phenoxyacetic acid exhibited vesiculation of the plasma membrane, mitochondrial swelling with disorganization of cristae, disruption of the chloroplast lamellar system, and dictyosomes with irregularly swollen cisternae. Ultrastructural details previously not reported for species of Chlorella were also observed: (1) presence of a crystalline pyrenoid with an 80 A periodicity, (2) a nucleolus made up of ribosome-like particles, and (3) smaller ribosomes in the chloroplast and mitochondria than in the cytoplasm.     

The Uptake of Growth Substances: X. THE ACCUMULATION OF PHENOXYACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID BY SEGMENTS OF AVENA MESOCOTYL

Segments of Avena mesocotyl were placed in buffered solutionsof phenoxyacetic acid (POA) or 2,4-dichlorophebnoxyacetic acid(2,4-D), containing carbon-14 in the carboxyl group, and thequantities of radioactivity taken up by the tissues measured.With freshly cut segments in solutions of 2,4-D there is accumulationof carbon-14, but the course of uptake is interrupted by a temporaryphase when some of the accumulated 2,4-D is released to theexternal solution. If after cutting the segments are first pretreatedby placing them for about 15 h in buffer, and then transferredto 2,4-D, there is progressive accumulation with no phase ofnet loss. Pretreated segments absorb greater quantities of either 2,4-Dor POA than freshly excised tissues. Following pretreatmentin buffer the course of uptake of POA is linear but for 2,4-Dthe course is curvilinear. However, after pretreatment withnon-radioactive 2,4-D the subsequent rate of uptake of radioactive2,4-D is constant over long periods. The uptake of radioactive2,4-D is largely independent of the concentration of non-radioactive2,4-D given during pretreatment. When segments which have absorbed 2,4-D-1-¹⁴C are transferredto buffer, a relatively small proportion of the carbon-14, the‘mobile fraction’, is released. The amount releasedfollowing different periods of uptake is constant whereas thelevel of non-mobile carbon-14, the ‘residual fraction’,rises progressively in step with accumulation. The uptake of POA and 2,4-D is accompained by the formationwithin the tissues of other radioactive substances. It is concludedthat the residual fraction is composed, at least in part, ofthese metabolic products and that accumulation and metabolicconversion are inter-connected. Dinitrophenol (DNP) slowly and progressively depresses the uptakeof POA whereas the uptake of 2,4-D is very rapidly arrested.However, after about 2 h, in the continued presence of DNP,uptake of 2,4-D restarts but the rate never attains that ofthe control. These divergent effects of DNP indicate that POAand 2,4-D are accumulated by different pathways.     

OLFACTORY RESPONSE OF THE GRASSHOPPER MELANOPLUS SANGUINIPES TO PLANT ODOURS AND VOLATILE COMPOUNDS

Abstract Electroantennograms (EAGs1 were recorded from male adults of Melanoplus sanguinipes to foliage odours from 5 plant species and 9 volatile compounds as well as their blends. Higher EAG responses were recorded for Louisianna sage and Alfalfa foliages, compared to other three gramineous plants. Among green odour chelricals, 6-carbon alcohols (e. g. E-2-hexen-1–01 and E-3-hexen-1–01] resulted in the highest EAG responszs. No significant differences among the pentenol, 3-pentanone and blank control were observed. In ternary and quaternary mixture tests of volatile compounds, the combinations with pentenol did not elicit greater amplitudes; thus pentenol and 3-pentanone were proved to be unimportant to the response of this generalist grasshopper. The EAG data are discussed with regard to the role of host plant volatiles in host plant orientation and selection by the grasshopper.     

黑蝗对植物气味及其挥发性化合物的嗅觉反应(英文)

本文使用触角电位技术研究了黑蝗雄虫的嗅觉反应,测试的材料包括5种植物叶片、9种植物挥发性气味化合物及它们的定量混合物。在5种植物材料中,路易斯安纳蒿和紫花苜蓿能引起更大的电位反应,而3种禾本科植物的反应相对较小。在绿色气味化合物中,6-碳醇类如E-2-hexen-l-ol和E-3-hexen-l-ol导致最高的电位反应,而pentenol、3-pentanone与空白对照间并无明显差异。在3种或4种挥发性化合物的混合物中,没有含pentenol的组合总是引起较高的电位。因此,该项研究证明pentenol和3-pentanone在这种多食性黑蝗的嗅觉定位中所起的作用不明显。另外,结合触角电位的数据资料,作者讨论了寄主植物挥发性化合物在该种蝗虫定位和选择寄主植物方面的作用。     

南水北调中线干渠异味物质时空动态及其影响因素

为认识南水北调中线干渠异味物质的时空动态,于2018年9月至2019年8月对干渠沿线9个样点开展了6种异味物质、藻类群落及理化因子的逐月同步调查;结果显示:二甲基异莰醇含量平均值为(7.431±9.631)ng/L,夏季略超出嗅阈值;β-环柠檬醛和β-紫罗兰酮平均值分别为(12.371±12.800)和(11.973±...