The Effects of Kinetin, Gibberellic Acid, and Light on Expansion and Cell Division in Leaf Disks of Dwarf Bean (Phaseolus vulgaris)

The effects of kinetin (Kn), gibberellic acid (G), and light(L) on cell expansion and division in disks from 6-day-old etiolatedprimary leaves of dwarf bean are described. Cell number wasdetermined by direct counting after disks were digested in apectinase/EDTA mixture to separate the cells. Kn increased leafexpansion wholly by increasing cell size. G also increased cellsize; it increased cell division in the dark but not in thelight. Light also increased cell size and cell division; iteliminated the effect of G on cell division but enhanced theeffect of G on cell expansion.     

Effect of 4,6-Dinitro-o-sec-butylphenol on Phosphorus Accumulation and Incorporation in Tomato Leaf Disks

The accumulation and incorporation of externally applied P³² into ATP and the effect of 4,6-dinitro-o-sec-butylphenol (DNBP) on these processes was studied, using tomato (Lycopersicon esculentum Mill.) leaf disks.

P³² was, in most part, actively accumulated into leaf disks with time and was incorporated into ATP and other organic phosphates. DNBP inhibited both P³² accumulation and ATP generation. The amount of inhibition increased with time of incubation.

It is concluded that P³² accumulation is related to ATP generation. Even though DNBP greatly inhibits phosphorus accumulation, there is little or no effect on its retention.

DNBP has the ability to uncouple oxidative phosphorylation. Therefore, it is assumed that its inhibitory effect on phosphate accumulation and generation of high-energy phosphorus esters is related to its inhibition of oxidative phosphorylation.

A method is described which appears to be satisfactory to determine the relative amounts of ATP and ADP in leaf disks labeled with P³².

     

Therapeutic Effect of Kinetin on Tobacco Alternariosis

LESIONS produced by Alternaris tenuis on tobacco leaves consist of fungal invaded, necrotic centres surrounded by well demarcated, non-invaded, chlorotic haloes^1,2, though necrosis does occur without chlorosis following infection of leaves in advanced senescence³. Alternariol monomethyl ether (AME)⁴ and tenuazonic acid⁵ have been implicated as chlorosis inducing metabolites (CIM) but other metabolites^6,7 may be involved. CIM are readily detoxified in young, living tissue⁶, though tenuazonic acid seems to be fairly stable⁵. Under uniform conditions, infection of progressively older leaf tissues results in lesions with chlorotic halos of increasing width^1,3 which suggests that the CIM are detoxified less readily or are synthesized more abundantly as the host tissue ages.     

Effect of Zeatin on H202 Scavenging System of Vitis vulpina Leaf Disks Under Salt Stress

Leaf disks of Vitis vulpina L. were incubated in hquid media containing 0,75,100, 125,150,200 and 225 mmol•L-1 NaCl with or without 1 μmol•L-1 zeatin, at 25 ℃ ,under 1 000 μmol • m-2 • s-1 continuous illumination, leaf relative permeability, contents of photosynthetic pigments and soluble protein, and activities of catalase (CAT), ascorbate peroxidase (AsA-POD) and guaiacol peroxidase(G-POD) were compared. The results showed that relative leaf permeability was increased following the increase of NaC1 concentration, whereas activities of leaf CAT, AsA-POD and G-POD, and contents of leaf photosynthetic pigments were reduced significanfiy. These effects of salt stress were significantly inhibited in the presence of zeatin. The ,relationship between relative leaf permeability and activities of H2O2 scavenging enzymes were discussed.     

Effect of Drying Methods on Quality of Leaf Protein Concentrate

Glutathione thiol esterase activity in cell extracts of a yeast: Saccharomyces cerevisiae was separated into three peaks when filtered on a Sephadex G-150 gel column. One of the enzymes in these peaks was purified. The enzyme was a single polypeptide chain with a molecular weight of 28,000 and catalyzed the complete hydrolysis of S-acetylglutathione and S-lactoylglutathione. S- Methyl-, S-hexyl-, S-glyceryl-, S-succinylglutathiones, and acetyl CoA were not hydrolyzed. In addition to the hydrolytic activity, the purified enzyme showed a group transfer activity and catalyzed the formation of acetyl CoA from S-acetylglutathione and CoA. The purified enzyme was not identical with glyoxalase II in molecular weight, substrate specificity, or behaviors toward inhibitors.     

Photoregulation of Anthocyanin Synthesis X. Dependence on Photosynthesis of High Irradiance Response Anthocyanin Synthesis in Brassica oleracea Leaf Disks and Spirodela polyrrhiza

The most effective spectral regions for anthocyanin productionin cabbage leaf disks and Spirodela are the red, blue and ultravioletA, with action in the far red (FR) minimal or nil. Phytochromeis involved in the photoregulation of anthocyanin productionin these two systems. The expression of the response dependsupon photosynthetic activity. Comparison with data from othersystems suggests that a spectral sensitivity with high efficiencyof red and blue and low or nil efficiency of FR might be a commonfeature of anthocyanin production in systems with a low phytochromecontent and dependent on photosynthetic activity for the expressionof the response. (Received January 6, 1984; Accepted June 30, 1984)     

Induction of Phenylalanine Ammonia-lyase in Xanthium Leaf Disks. Photosynthetic Requirement and Effect of Daylength

A cycloheximide-sensitive increase in the activity of phenylalanine ammonia-lyase (EC 4.3.1.5) occurs in Xanthium leaf disks exposed to light. Radioactive ammonia-lyase has been isolated by means of sucrose density gradient centrifugation and starch gel electrophoresis from disks fed l-isoleucine-U-(14)C or l-arginine-U-(14)C. The incorporation of radioactive amino acids into phenylalanine ammonia-lyase together with the inhibitory effects of cycloheximide indicate that the observed increase in enzyme activity involves the induction of lyase synthesis.The light-dependent synthesis of the ammonia-lyase is completely inhibited by 50 mum 3-(4-chlorophenyl)-1,1-dimethylurea (CMU) indicating that photosynthesis is involved. Only a trace quantity of some photosynthetic product must be needed because half light saturation occurs at very low intensity (ca. 30 ft-c). Exogenous carbohydrate is also required for continuing enzyme synthesis over a 72 hr period. But carbohydrate does not replace the photosynthetic requirement in darkness.Enzyme formed in light disappears rapidly from disks placed in the dark. The decay of ammonia-lyase activity follows first order kinetics. The half-life of the lyase ranged from 6 to 15 hr in leaf material used. Cyoloheximide inhibits the decay of lyase activity. Thus the maintenance of turnover in Xanthium leaf disks requires de novo synthesis of protein. That turnover, i.e., degradation as well as synthesis of lyase protein occurs is suggested by the apparent loss of radioactive ammonia-lyase from leaf disks placed in darkness. Light-induced synthesis coupled with rapid turnover can produce a diurnal fluctuation of ammonia-lyase activity in Xanthium leaf disks. Alternating periods of enzyme synthesis and degradation were observed in disks exposed to 24 hr cycles of light and dark. The average level of enzyme activity maintained in the tissue was directly related to the length of the light period. Induction of lyase synthesis was also observed in excised leaves and to a lesser extent in leaves of whole plants.     

Effect of Kinetin on Ribosomes of Excised Barley Leaves

The changes in the amount and the composition of ribosomes in excised barley leaves floated on water or on 10 mg/l kinetin solution in the dark were examined. The rapid loss of polyribosomes and ribosomes in leaves floated on water was greatly retarded by kinetin. The ribosomes-polyribosomes which originally contained 49 per cent protein showed substantial decline in protein content in leaves floated on water but only slight decline in leaves floated on kinetin solution. It is suggested that kinetin by stimulating RNA synthesis and by suppressing the activities of rihonuclease and peplidase may preserve the ribosomes in excised leaves.     

The Effects of Nitrate Supply and Grain Reserves on Fraction I Protein Level in the First Leaf of Barley

The timing and rate of nitrate application to barley seedlingsgrown under control and shade conditions can appreciably affectthe maximum amount of Fraction I protein attained in the firstleaf lamina. In unshaded seedlings early application resultsin a higher maximum amount of Fraction I protein per lamina,but not per unit lamina fresh weight. Late application of nitratehowever delays the age at which Fraction I protein reaches amaximum both in absolute terms and as a proportion of totalsoluble protein. For both control and shade-grown material earlyand higher rates of nitrate supply increase the maximum amountof soluble protein in the leaf but not the proportion representedby Fraction I protein. Lower rates of nitrate application havemuch less effect on first-leaf protein synthesis when applicationis given late. This is thought to be due to competition fromthe rapidly developing second leaf. Studies on the soluble protein content of shaded first-leaflaminae have shown that although grain size affects the maximumamount of Fraction I protein attained it does not alter theage at which this is attained; nor is the proportion of thetotal soluble protein accounted for by Fraction I protein affectedby grain size or grain nitrogen content. A model is proposed to explain the contribution made by grainreserves and exogenous carbon and nitrogen supply to the developmentof the soluble protein content of the first leaf.     

The Implication of Auxin in the UV Promoted Expansion of Etiolated Bean Leaf Disks

A promotion of expansion of etiolated bean leaf disks by ultraviolet (UV) radiation was confirmed. The optimum conditions for the effeet were found to be 5 seconds UV exposure followed by 24 hours of incubation at 25°C and pH 6.2. Macerations and sections of the treated and control disks indicated that the basis of the response was an increase in the number of cells in the UV treated disks. Experiments with indolebutyric acid (IBA) and p-chlorophenoxyisobutyric acid (PCIB) indicated that the UV apparently acted to reduce a superoptimal endogenous auxin level to an optimum level which resulted in promotion of the expansion.     

The Effect of Kinetin on the Occurrence of Acid Auxin in Coleus blumei

Excised shoots and potted plants of Coleus blumei Benth, were subjected to different treatments with kinetin solutions. Control treatments were made with water. Free and bound auxin were extracted with ether. The acid fractions were purified by electrophoresis to remove all traces of kinetin, and were then analyzed with the Avena straight-growth test. As compared with the controls, kinetin treatment increases the bound auxin, whereas the corresponding free auxin is unchanged. Also methanol extracts of treated stems contain more acid auxin than corresponding extracts of water-treated stems. This indicates that on methanol extraction not only free auxin but also some bound auxin is obtained. The extracted auxin behaves like indoleacetic acid in paper chromatography with four different solvent systems, as well as in gel filtration through Sephadex. New formation or decreased breakdown of auxin seem the most likely explanations for the observed effects of kinetin.     

羽衣甘蓝授粉过程中柱头蛋白质的泛素化

分析自花授粉与异花授粉后的羽衣甘蓝柱头蛋白质泛素化变化的结果表明,自花授粉30min后的柱头蛋白质泛素化水平显著增加,45min时达到峰值;异花授粉的柱头蛋白质泛素化水平没有变化。     

Hormonal Induction of Vascular Differentiation in Cultured Zinnia Leaf Disks

Mesophyll cells differentiated into tracheary elements whenZinnia leaf disks were cultured in media containing sufficientauxin and cytokinin. Moderate increases in the levels of phytohormonesinduced the recruitment of adjacent cells into the preexistingvasculature, resulting in the "expansion" of leaf veins. Higherhormonal concentrations induced unpatterned differentiationinto tracheary elements throughout the mesophyll and epidermis.This novel system should facilitate the study of organized vasculardifferentiation. (Received July 30, 1988; Accepted October 31, 1988)     

The Relation Between Ion Absorption and Protein Synthesis in Beet Disks

Disks of red beet storage tissue were incubated under asepticconditions permitting the development of various metabolic processescommonly associated with aged disks, and the effects of chloramphenicoland puromycin on protein synthesis, on the development of invertaseactivity and ion absorption capacity, and on ion absorptionper se were determined. Low concentrations of chloramphenicoland puromycin inhibit the development of ion absorption capacitybut stimulate invertase development and protein synthesis, whilehigher concentrations inhibit all three processes. In contrastion absorption itself is unaffected by puromycin, but is sensitiveto quite low concentrations of chloramphenicol The D-threo andL-threo isomers of chloramphenicol have sharply contrasted effectson the development, as distinct from the utilization, of ionabsorption capacity. The D isomer inhibits the development ofion absorption capacity more effectively than the L isomer whichin turn inhibits absorption more effectively than the D isomer. A reappraisal is made of the hypothesis that ion absorptionis directly linked with protein turnover and to account forthe results a model is proposed in which D-threo-chloramphenicolis active both as an uncoupler of oxidative phosphoryalationand as an inhibitor of protein synthesis, while L-threo-chloramphenicolacts only in the former capacity and puromycin only in the latter.It is concluded that the inhibition of ion uptake by chloramphenicolcannot be attributed to a contemporaneous effect on proteinsynthesis. However, the results are consistent with the involvementof ATPase proteins in ion uptake.