Response of Substituted Indoleacetic Acids in the Indolo-α-pyrone Fluorescence Determination

The method of indolo-α-pyrone fluorescence-determination of indoleacetic acid was investigated to study possible interference from 4-chloro-indoleacetic acid and 5-hydroxyindoleacetic acid, which occur naturally. Both compounds show about 40% of the fluorescence of indoleacetic acid after conversion into their a-pyrones. Other halogenated indoleacetic acids show between zero and 60% of the fluorescence of indoleacetic acid. It is concluded that the concentration of indoleacetic acid cannot be determined in crude extracts in the presence of 4-chloro- or 5-hydroxy-indoleacetic acid, because separate determinations of each of these compounds are not possible by changing the excitation or fluorescence wave-lengths of the testing equipment.     

Cytokinin-controlled Indoleacetic Acid Oxidase Isoenzymes in Tobacco Callus Cultures

Indoleacetic acid oxidase in tobacco callus tissues (Nicotiana tabacum L., cultivar White Gold) was resolved into seven anionic isoenzymes by polyacrylamide gel disc electrophoresis. Different concentrations of kinetin and zeatin in the presence of indoleacetic acid affected the level of this enzyme, particularly two fast-moving isoenzymes, A₅ and A₆. The optimal concentration of kinetin was 0.2 μm; increasing concentrations above this level progressively lowered the total activity of indoleacetic acid oxidase and repressed the development of isoenzymes A₅ and A₆. Actinomycin D and cycloheximide inhibited the development of these two isoenzymes under the influence of 0.2 μm kinetin, suggesting a requirement for RNA and protein synthesis. The cytokinin-promoted indoleacetic acid oxidase isoenzymes A₅ and A₆ increased with time and paralleled the dry weight increase of tobacco callus tissues, but the total activity of indoleacetic acid oxidase per unit dry weight of tobacco callus varied with time depending on the stage of plant growth.     

Deoxyribonucleotide Pools in Plant Tissue Cultures

Two dimensional thin-layer chromatography on anion-exchange cellulose enables the separation of the normally occurring ribo- and deoxyribonucleoside triphosphates. This technique was applied to perchloric acid extracts of callus tissue of sycamore and tobacco and of pine pollen grown in ³²P-orthophosphate labelled media to quantitate the nucleoside triphosphate pools under different growth conditions. The results showed that the ratio of the deoxyribonucleo-side triphosphates to their corresponding ribonucleoside triphosphates is low in plant cells, similar to the ratio previously found for animal cells. During the period of most rapid DNA synthesis in the callus tissue, the deoxyribonucleoside triphosphate pools reach their highest values. This effect is also demonstrated with cells of Escbericbia coli.     

Effect of Indoleacetic Acid on the Abscisic Acid Level in Stem Tissue

Excised stem sections from growing plants of Populus tremula L. and Pisum sativum L. including lateral buds were treated with indole-3-acetic acid in a phosphate buffer solution. In control sections the level of the abscisic acid-like inhibitor decreased strongly during 24 h as did the level of the endogenous auxin. Exogenous indoleacetic acid counteracted the decrease in the inhibitor level to a considerable extent. Implications of this auxin effect in relation to apical dominance are discussed.     

Anatomy of Maize Tissue Cultures

Tissue cultures of Zea mays L. derived from four different somatic sources all appeared to grow as callus. Microscopic examination, however, showed this growth to be merely an aberrant root-like form. A continium in the degree of aberrant root behavior, ranging from cultures appearing very root-like to those visibly indistinguishable from callus, was recognized. The continuum and ultimately the callus appearance resulted from increasing inhibition of root elongation coupled with strong enhancement of branch root initiation. This aberrant form of root growth was apparent in all cultures observed. Tissue source and growth regulator treatment interacted to shift the growth form within the extremes of the continuum but in no case was the root-like mechanism of proliferation disrupted, even during extended subculture. Removal of exogenous growth regulators from the culture medium simply allowed outgrowth of existing root primordia as normal roots and this accounts for the characteristic ease of rhizogenesis from what has been called maize callus.     

Some Characteristics and Inhibitors of Indoleacetic Acid Oxidase from Tissue 2

Extracts from tissue cultures of crown-gall from Parthenocissuscatalysed the destruction of indoleacetic acid in vitro withoptimum activity at pH 4·5. The presence of two co-factors,Mn⁺⁺ and 2,4-dichlorophenol, was necessary for this activity,which was found to be strictly aerobic. Chlorogenic acid, caffeic acid, scopoletin, ferulic acid, andgibberellic acid markedly inhibited IAA-destruction. Chlorogenicacid inhibition was reversed by the addition of H₂O₂. Chlorogenicacid was not oxidized by the IAA-destroying system and did notbehave as a competitive inhibitor. The IAA-oxidase extract manifested peroxidase and phenolaseactivity with catechol and pyrogallol as substrates. However,this activity was greater at pH 7·0 than at the optimumfor IAA-oxidase activity, pH 4·5. Further evidence ofthe existence of these two enzymes in the intact tissue wasdemonstrated by histochemical studies. In tissue slices, peroxidaseactivity was very high and widely distributed while phenolaseactivity was low and restricted to localized centres of thetissue.     

Lignin Biosynthesis Studies in Plant Tissue Cultures

Lignin, a phenolic polymer abundant in cell walls of certain cell types, has given challenges to scientists studying its structure or biosynthesis. In plants lignified tissues are distributed between other, non-lignified tissues. Characterization of native lignin in the cell wall has been difficult due to the highly cross-linked nature of the wall components. Model systems, like plant tissue cultures with tracheary element differentiation or extracellular lignin formation, have provided useful information r...     

Lignin Biosynthesis Studies in Plant Tissue Cultures

Lignin, a phenolic polymer abundant in cell walls of certain cell types, has given challenges to scientists studying its structure or biosynthesis. In plants lignified tissues are distributed between other, non-lignified tissues. Characterization of native lignin in the cell wall has been difficult due to the highly cross-linked nature of the wall components. Model systems, like plant tissue cultures with tracheary element differentiation or extracellular lignin formation, have provided useful information related to lignin structure and several aspects of lignin formation. For example, many enzyme activities in the phenylpropanoid pathway have been first identified in tissue cultures. This review focuses on studies where the use of plant tissue cultures has been advantageous in structural and biosynthesis studies of lignin, and discusses the validity of tissue cultures as models for lignin biosynthesis.     

Staining and Coating Roller-Tube Tissue Cultures

Decanted roller-tube tissue cultures are fixed either by oven drying (60-63°C) for 3 hr or by methyl alcohol for 5 min and stained within the tube with Harris hematoxylin (diluted 1:1) and 4.4% alcoholic eosin. Oven drying before staining emphasizes cytoplasmic detail, whereas methyl alcohol produces distinct nuclear detail. After dehydrating and clearing by alcohols and xylene, 1.0 ml of Fisher's Permount is pipetted into the roller tube which is held at a 5-10 angle, rotated until the tissue sheet is covered, and placed in a paraffin oven at this angle for 16-20 hr. With a few exceptions, a majority of tubes showed no tissue drying and only minimal fading after 4-6 mo.     

4种红景天植物的组织培养研究

以大花红景天、云南红景天、长鞭红景天和库页红景天的茎和叶为外植体进行组织培养,结果表明：大花红景天以茎为外植体诱导芽效果最好,其它3种红景天以叶为外植体诱导芽效果最好。云南红景天和长鞭红景天适合的芽诱导激素组合是0．1mg／L NAA和2．5mg／L 6-BA的组合,在该激素水平下两种红景天的出芽频率分别达到71％和84％;大花红景天和库叶红景天适合的芽诱导激素组合是0．5mg／L NAA和2．5mg／L 6-BA的组合,在该激素水平下两种红景天的出芽频率均达到80％。长鞭红景天和库叶红景天在添加IBA的培养基上容易生根形成完整植株,生根率分别达到87％和73％;经过炼苗后,长鞭红景天再生苗能够成功移栽,成活率达66％。