Auxin action: the search for the receptor

Abstract. The molecular specificity of the substances which have auxin activity implies the existence of specific receptors. There have been many efforts to identify and isolate these receptors on the assumption that they should bind auxins with affinities coordinate to their activities in bioassays. However, the known complexity of auxin uptake and metabolism make this assumption seriously deficient. Although several such binding sites have, in fact, been identified, proof of a connection between these sites and auxin action has been lacking. Definite proof would include a requirement that the site be reconstituted, together with the appropriate macro-molecular machinery, to construct a model of an auxin response. At the moment, our ignorance of the biochemistry and molecular biology of auxin growth responses makes such a proof difficult. However, two avenues of research promise to accelerate the rate of progress. The increasingly potent tools of molecular biology should soon allow the dissection of auxin-regulated gene expression, while improved knowledge of plasma membrane proton pumps and the mechanism of cell wall biosynthesis should produce, in parallel, an understanding of the auxin regulation of acid growth.     

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。     

新疆20种药用植物的染色体观察

本文对在新疆生长和引种栽培的10科20种药用植物染色体进行了计数和研究,其中5种进行了核型分析,6种为首次报道。     

The influence of food plant dispersion on caterpillar searching success

Abstract. 1. Collards (Brassica oleracea L.) grown in clumps were more difficult for unstarved, early instar cabbage white caterpillars (Pieris rapae L.) to find than collards spaced at regular intervals, although total plant densities were identical.
2. Early instar, unstarved larvae are less mobile than later instar larvae (our data) or starved larvae (Jones' 1977 data).
3. Starved larvae and late instar larvae tend to find plants more readily than do unstarved or younger larvae.
4. We contend that larval mobility governs the success of searching caterpillars and their sensitivity to variations in plant dispersion.
5. Our results show that the dispersion of targets can influence searching success even though target density is constant. This means that the degree of clumping in host plants is capable of influencing their availability to herbivores.     

Differentiation of cotton fibers from single cells in suspension culture

Summary A cotton cell suspension culture has been developed that provides unique opportunities for plant biologists to investigate early developmental events regulating cotton fiber properties, plant cell elongation, and cell wall biogenesis. The suspension culture was derived from cells of cotton (Gossypium hirsutum L.) ovule callus. These cells undergo the stages of fiber development previously described for in vivo fiber development. Fibers range in length up to 11 mm and have secondary walls. Supported by the U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Laboratory, New Orleans, Louisiana, and Cotton Incorporated, Raleigh, North Carolina.     

Influence of 2-(3,4 dichlorophenoxy)-triethylamine on photosynthesis of Phaseolus vulgaris L.

The effect of foliar sprays of the growth regulator 2-(3,4 dichlorophenoxy)-triethylamine (DCPTA) on net photosynthesis (P_n) by intact bean plants depended upon concentration and the stage of development of the leaves. A single foliar spray of 2.0 mM DCPTA reduced P_n when applied to young expanding leaves but had little effect on fully expanded leaves. Lower DCPTA concentrations (0.2 to 0.8 mM) had no effect on P_n, unless applied more than once which resulted in reduced P_n. The DCPTA-induced inhibition of P_n was associated with chlorosis and aberrations in chloroplast ultrastructure. DCPTA did not affect stomatal resistance. When applied to detached leaf disks in the dark, DCPTA retarded the normal loss of chlorophyll suggesting that DCPTA may have anti-seneseent properties.Abbreviations DCPTA 2-(3,4 dichlorophenoxy)-triethylamine - P_n net photosynthesis - I_s stomatal diffusive resistance     

An analysis of tobacco mosaic virus replicative structures synthesized in vitro

Summary The RNA structures synthesized in vitro by a crude enzyme complex from tobacco mosaic virus (TMV)-infected leaves have been analyzed; the major viral-specific products were similar to TMV-replicative form (RF) and-replicative intermediate (RI) in electrophoretic behavior and ribonuclease sensitivity. Synthesis of these RF-like and RI-like structures neither required nor responded to added viral RNA, but did require all four ribonucleotide triphosphates. Enriched radiolabeled RF-like and RI-like RNA fractions were isolated from non-denaturing agarose gels by electroelution and hybridized to a collection of TMV sequences cloned into bacteriophage M13. Enriched RF-RNA hybridized to sequences of both plus and minus polarity, while enriched RI-RNA hybridized only to inserts of minus polarity, indicating only plus strand synthesis in this fraction. Most of the label incorporated into the plus strand of the enriched RF-RNA was found near the 3-end of this strand, while most of the label incorporated into enriched RI-RNA was found several hundred bases from the 5-end of the plus strand.Paper presented at the first International Congress of Plant Molecular Biology (Savannah, GA, 1985).