EFFECT OF AUXIN AND ANTIAUXIN ON CELL ELONGATION IN YEAST

By using a cytoplasmic mutant strain of yeast deficient in aerobicrespiration, it was demonstrated that, in the concentrationof 10–20 mg/l, indole-3-acetic acid and a.naphthaleneaceticacid promoted elongation of yeast cells, while acetic acid hadno such effect. An antiauxin, 2, 4, 6-trichlorophenoxyaceticacid, completely reversed the above-mentioned effect of auxin. The effect of auxin could be observed before any significantcell multiplication occurred. (Received February 7, 1963; )     

EFFECT OF GIBBERELLIC ACID ON ELONGATION AND NUCLEIC ACID SYNTHESIS IN ETIOLATED ALASKA PEA EPICOTYL

The following results were obtained using etiolated Alaska pea epicotyls. Gibberellic acid (GA) had the remarkable effect on the elongation in part I (elongating region) of epicotyls, whereas it had little effect on that in part II (mature region) of epicotyls. In cortex of part I and II of epicotyls, the cell number in longitudinal direction was hardly affected by GA. On the increase in width of epicotyls, GA was hardly effective in any parts of epicotyls. In both part I and II GA enhanced the incorporation of ³²P into all nucleic acid fractions prepared by methylated albumin kieselguhr (MAK) columns, i.e. sRNA, DNA and rRNA + mRNA. In part I the net increase in DNA and RNA content during the incubation period was slightly promoted by GA, whereas in part II the net decrease in both nucleic acids content was slightly promoted by GA. The relationship between GA-induced growth and nucleic acid synthesis is discussed.     

EFFECT OF AUXIN AND GIBBERELLIN ON OSMOTIC VALUE OF PEA STEM SECTIONS

When etiolated pea stem sections were floated on solutions ofIAA and gibberellin, the osmotic value of the tissue juice decreasedmore than expected from dilution due to water absorption. Whenstem sections smeared with lanolin pastes of IAA and gibberellinwere kept in moist air, IAA caused anatonosis and gibberellincaused catatonosis. (Received June 12, 1961; )     

EFFECTS OF GIBBERELLIN AND AUXIN ON THE EXTENSIBILITY OF THE PEA STEM

Excised pieces of etiolated Alaska pea stem were pulled longitudinallyor transversely, and elongation or bending was measured. Pieces treated with IAA were stretched conspicuously when longitudinalforce was applied, and continued elongating under the forceat approximately the same rate as without it. Control piecesbehaved in a similar way, but on a smaller scale. Pieces treatedwith gibberellin scarcely elongated under the force, but elongatedwithout it. IAA-treated stem pieces were bent by transverse force more easily,and gibberellin-treated ones less easily than control. (Received February 1, 1960; )     

THE EFFECT OF COTYLEDON EXCISION ON THE GROWTH OF PEA SEEDLINGS

Pea plants grown under controlled conditions for 28 days were sampled nine times during this growth period. On each sampling day 80 plants were harvested. Cotyledons were excised from 40 plants and the root-shoot axis allowed to continue growth. The other 40 plants were divided into roots, shoots, and cotyledons; the dry weights of alcohol-water extracts and residues from these organs were determined. Shoot lengths, numbers of nodes, buds, flowers, and fruits of 28-day-old plants, whose cotyledons were excised at different times, were determined. These data indicate that cotyledon excision after the 13th day has no apparent effect on seedling growth, whereas excision before the 13th day reduces growth. Glucose-U-C¹⁴ supplied to attached cotyledons of 6- and 16-day-old seedlings resulted in no major difference in the distribution pattern of recovered label throughout the plant even though 16-day-old cotyledons were depleted of their normal endogenous food reserve.     

EFFECT OF ETHYLENE ON CELLULAR DIFFERENTIATION IN ETIOLATED PEA SEEDLINGS

Ethylene (50 ppm) and 2,4-D (1 mm ) inhibit xylogenesis and completely prevent fiber lignification in the third internode of etiolated pea seedlings (Pisum sativum var. Alaska) during 96–240 hr of treatment. When ethylene is removed after 72 hr, normal differentiation resumes; thus the gas causes no irreversible damage to the cells. A combined treatment with 50 ppm ethylene and 50 μm 2,4-D or treatment with 1 mm 2,4-D alone causes inhibition similar to that observed with 50 ppm ethylene, and 50 μm 2,4-D is partially effective. The inhibition of xylogenesis and fiber lignification caused by 2,4-D is partly or wholly due to auxin-induced ethylene production.     

A KINETIC STUDY OF GROWTH MOVEMENTS AND PHOTOMORPHOGENESIS IN ETIOLATED PEA SEEDLINGS

The kinetics of the effects of inductive photomorphogenically active light on etiolated peas have been studied by means of time-lapse photography. The effects noted include: (1) A light-induced decrease in the rate of stem elongation, beginning about 6 hr after the light treatment, and ending about 18 hr later. (2) A light-induced opening of the apical hook, beginning ca. 2–5 hr after light treatment, and reaching its peak rate ca. 6 hr later. (3) A light-stimulated circumnutation, starting usually about 15–22 hr after the light, and resulting in a decreased period of oscillation (from ca. 86 to ca. 76 min) and an increased amplitude (from 15° total angular displacement to about 40°). (4) A promotion of terminal bud growth, known from previous work to start at about 4 hr after irradiation and to reach a peak about 12 hr later. (5) A “bobbing” movement of the apex, apparently involving reversible hook and stem oscillations, which appears to be of endogenous origin and insensitive to light. These data furnish a kinetic background against which proposed biochemical mechanisms of de-etiolation can be assessed.     

生长素和细胞分裂素在调节豌豆根系缺铁反应中的作用

在水培条件下研究了生长素和细胞分裂素对两种基因型豌豆根系铁还原力的影响。结果表明,去顶,顶端涂抹ＮＡＡ和茎基部涂抹ＣＭＥ都不影响豌豆根系铁还原力。茎尖,茎基部和根系的ＩＡＡ、Ｚ／ＺＲ含量与根系铁还原力之间没有明显的相关性。     

矿质营养对生长素代谢影响的研究现状与展望

植物从环境中吸收的矿质元素直接参与植物生理代谢,植物内源激素对植物生理代谢具有重要的调节作用,矿质营养与植物内源激素的相互关系一直是植物营养研究的重要内容。生长素是植物五大内源激素之一,对细胞的分裂和伸长具有重要的调节作用。本文从矿质营养对ＩＡＡ的量及分布,矿质营养对ＩＡＡ合成,矿质营养对ＩＡＡ运输,矿质营养对ＩＡＡ的转化等方面对矿质营养与生长素的关系的研究进展进行了概述,并对矿质营养与生长素的关系的进一步研究进行了展望。     

THE EFFECT OF AGITATION AND TURBULENCE OF THE GROWTH MEDIUM ON THE GROWTH AND VIABILITY OF MICROCYSTIS

SUMMARY

Observation of natural blooms of Microcystis, suggested that increased turbulence plays a role in retarding bloom formation of Microcystis. In laboratory experiments the influence of turbulence mediated by a magnetic stirrer on the growth and viability of Microcystis in batch cultures was determined. The different turbulences (0, 25, 75, 126, 209 and 314 cm sec^?1 linear velocity) had no effect on the growth rate. There was a highly significant correlation between the linear velocity and percentage viability as determined by a plating and serial dilution method. The viability ranged from 0,8% for stationary cultures to 99,2% for vigorously stirred (314 cm sec^?1 linear velocity) cultures.     

THE RELATIONSHIP OF GIBBERELLIN AND AUXIN IN PLANT GROWTH

No synergism was found between IAA and gibberellin in the Avenucurvature test and this bioassay thus measures changes in diffusibleauxin resulting from gibberellin treatment and not a synergisticaction of the gibberellin on the curvature response to auxin.Gibberellin treatment causes an increase in diffusible auxinfrom the stem apex of dwarf pea (Pisum sativum L. var. LittleMarvel) 24 to 48 hours before the elongation response in thestem. The increase in diffusible auxin in the stem apex of Centaureacyanus L. var. Blue Boy occurs four to six days before the boltingresponse to gibberellin treatment under short days. The stemtissues of both the dwarf pea and Centaurea show an elongationresponse to IAA when the IAA is applied in a manner simulatingthe stem apex. Thus the growth of the dwarf pea and the boltingof Centaurea brought about by treatment with gibberellin aredependent on an increase in diffusible auxin. ¹Present address: Biological Institute, College of General Education,University of Tokyo, Komaba, Meguro, Tokyo.