Occurence of a Phosphodiesterase in the Insoluble Fractions from Wheat Seedlings

The volume of carbon dioxide evolved in a shaking apparatus was measured at fixed intervals, and it was confirmed that the fermentation of dry yeast generally depends on three factors and that they are represented with an initial fermenting activity, a power which recovers fermenting activity, and a maximum fermenting activity. This expression of fermenting power was compared with usual expressions and it was proved to be more reasonable, particularly, for deciding the initial fermenting activity.     

小麦幼苗根系镉螯合素

从经Cd~(2+)处理的小麦幼苗根系中分离得到一种镉结合复合物(Cd-BC)。通过SephadexG75,DEAE-52柱层析纯化,鉴定了此复合物性质:(1)紫外吸收光谱在255～265 tim间有一个“肩”,A_(250)/A_(280)>1;(2)在Sephadex G75柱层析上的表观分子量约为10kD,但在SDS-聚丙烯酰胺凝胶电泳上呈现的条带紧接着前沿,分子量非常小;(3)氨基酸组分分析,约90％的氨基酸残基为Glu/Gln,Cys和Gly,三者比例约为4:4:1。结果说明小麦幼苗根系Cd-BC是寡聚肽,是植物镉螯合素(Cd-PCs)的聚合体。     

The Nutrition of Excised Wheat Roots

From an investigation of the nutrient requirements of Hilgendorf wheat roots, glucose emerged as the only suitable source of carbon and energy, and thiamine as the only vitamin necessary. The roots had the ability to utilise nitrogen from calcium nitrate, urea, alanine, glutamine, allantoin, and hydrolyzed casein.     

DCPA Causes Cell Plate Disruption in Wheat Roots

Light and electron microscopy were used to investigate the effectsof the herbicide DCPA (dimethyl tetrachloroterephalate) on wheatroot meristems. Three different sorts of disruption are found.In the epidermal cells, the walls are incomplete and/or curved,as well as being oriented in directions other than perpendicularto the long axis of the root. In developing cell plates, phragmoplastmicrotubule arrays are oriented in many directions in this layer,probably accounting for the wall abnormalities. In the calyptrogenand cortical layers, no walls or incomplete walls are formedbetween the nuclei, so that these cell layers are essentiallyone large cell with multiple nuclei. This effect has not beenobserved for any other herbicide. Prometaphase figures witha few microtubules and multipolar mitosis are the predominantabnormalities in the meristematic zone. Aberrant cell wallsare also found in this tissue layer. These data indicate thatDCPA is effective at disrupting phragmoplast micTotubule arraysand cell wall formation. Herbicide, mitosis, cell plate, cell wall     

Tissue Tensions during Cell Elongation in Wheat Roots and a Comparison with Contractile Roots

A study has been made of tissue tensions in growing Triticum roots. After the initial phase of elongation with both a lateral and an exponential longitudinal growth, the tissues are under strong longitudinal stress. Plasmolysis in situ or splitting of the root in the pericyclic region causes an increase in length of the perivascular part. Freed from the stele the perivascular part contracts on plasmolysis. During the following only longitudinal growth, the stress decreases under decreased root diameter. When elongation has ceased, the root in situ contracts on plasmolysis. It is suggested that during radial growth longitudinal stresses are built up, which are released when the stele catches up with the growth of the cortex. The similarity to conditions in contractile roots of Arum (Lamant and Heller 1967) is pointed out. A difference is found in the polarity of growth and thus in the mode of release of the stresses. The cause of the tensions and methodical difficulties are discussed.     

一种以幼根K+外漏量鉴定小麦耐盐性的方法

经100 mmol·L-1 NaCl处理的小麦幼根、胚芽和胚芽鞘的K+净外漏量和K+净外漏率显著增加,盐敏感小麦品种'LM15'的幼根K+净外漏量和净外漏率明显大于耐盐品种'DK961';2个品种小麦幼根K+外漏率差异主要是由其成熟区引起的.幼根K+净外漏量及净外漏率均与小麦的耐盐性呈负相关,因此认为幼根K+外漏可以作为快速鉴定NaCl胁迫下小麦耐盐性的指标.     

小麦根系生长对缺磷胁迫的反应

研究了缺磷诱导小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍＬ．）根系生长的反应,小麦根轴的生长与植株内外的磷浓度均呈显著的负线性关系。分根实验证明,随着低磷营养液中根比例的增加,在供磷水平不同的分根盒侧的根轴长度的均增加,这说明根轴生长是受体内磷浓度调控的。植株体内磷浓度的处理后１ｄ开始变化,而在不同供磷水平营养液中小麦根轴长度的差异达到显著水平的时间是处理后的第８天,说明植株体内磷浓度的变化可能是小     

Resistance to Water Flow in the Seminal Roots of Wheat

Water uptake by the seminal root system of wheat is describedby a model which incorporates radial and axial resistance toflow in the root and the resistance to flow in the soil. Inan experiment where wheat plants were dependent on subsoil waterextracted from below 45 cm by one, three, or five seminal roots,calculations indicated that the axial resistance was the dominantresistance within the soil-root system and that flow rate changedpredictably with changing axial resistance. The model also indicatedthat the observed shape of the metaxylem vessel in the seminalaxes has important effects on the pattern of water uptake.     

Studies of the Growth in Culture of Excised Wheat Roots

Aeration of root culture medium with air containing 5 % or 10 % CO₂ enhances growth, particularly lateral initiation and growth, compared with aeration wilh air or CO₂-free air. This beneficial effect of enhanced CO₂ pressure on the growth of cultured roots of Atson Elite 56 wheat ean also be demonstrated in presence of a high (40 %) and inhibiting level of oxygen. ¹⁴C labelling from a carbonate–bicarbonate solution of pH 7.0 by cultured wheat roots is enhanced by light and this labelling is not inhibited by the presence of 1 % ethyl urethane.     

Studies of the Growth in Culture of Excised Wheat Roots

Evidence is presented that the growth of cultured wheat roots is enhanced in closed culture systems not only by carbon dioxide but by a further and apparently very volatile product of root metabolism. The formation of this second growth-stimulating substance is not considered to depend upon a reduction of oxygen tension in the culture system. Unlike ethanol the activity of the volatile promoter does not depend upon illumination of the cultures. The volatile promoter cannot be effectively absorbed by a number of gas absorbents. Attempts to demonstrate ethylene production by the roots have been unsuccessful.     

Localization of Structural and Regulatory Genes for Phosphodiesterase in Wheat (TRITICUM AESTIVUM)

Genes (Pde-A3; Pde-B3; Pde-D3) for phosphodiesterase (PDE; E.C. 3.1.4.1.) isoenzymes in hexaploid wheat were located on the three homoeologous chromosomes of group 3 by testing the electrophoretic banding pattern of monosomic, nullisomic and nullisomic/tetrasomic compensation lines of "Chinese Spring" variety. In plants nullisomic for chromosome 5B, the 3D structural gene is not expressed and this lack of expression can be overcome by four doses of either homoeologous chromosome 5A or 5D. Our data conclusively indicate that there are genes on group 5 chromosomes which positively control the expression of the 3D structural gene. In addition, the expression of the "regulatory genes" is dosage dependent. Thus, our study reveals a complex interaction of the three genomes of wheat for regulation of PDE gene expression.