GIBBERELLIN AND AUXIN RELATIONSHIPS IN ABSCISSION

Gibberellic acid (GA) has no effect on abscission when applied proximally or distally to the abscission zones of debladed petioles of Coleus. Application of GA to the stem apex increases the rate of abscission of debladed petioles. The effect on abscission is accompanied by an increase in the level of endogenous auxin in the stem. Correspondingly proximal applications of indoleacetic acid (IAA) accelerate abscission, whereas the longevity of the debladed petiole approaches that of the intact leaf only in the presence of a continuous distal supply of IAA. No correlation is found between petiole elongation and its longevity. The experimental data support the view that auxin acts at the abscission zone in regulating separation processes and that the effect of GA is through its effect on the level of endogenous auxin.     

FIBER INITIATION ON THE COTTON OVULE (GOSSYPIUM HIRSUTUM)

Cotton ovules at the stage of fiber initiation were studied with a scanning electron microscope. On the day before anthesis the anatropous ovule had many anomocytic stomata, especially on the chalazal end. At anthesis, fibers first appeared at the crest of the funiculus and then around the lateral circumference of the ovule. Fiber initials were delayed for a few hours at the chalazal cap and for 3 or 4 days at the extreme end of the micropylar region. The morphological differentiation of a fiber began when an epidermal cell rounded up and protruded. After a brief period of diametric expansion, the initial began elongation toward the micropylar end. Between 2 and 3 days of age the fibers segregated into small groups, developed tapered tips, and began spiral growth. Fiber density was about 3,300 fibers per mm², and the ratio of fiber initials to total epidermal cells was 1:3.7 at anthesis.     

GENETIC DIVERSITY IN GOSSYPIUM HIRSUTUM AND THE ORIGIN OF UPLAND COTTON

Gossypium hirsutum has a large indigenous range encompassing most of Mesoamerica and the Caribbean, where it exhibits a diverse array of morphological forms spanning the wild-to-domesticated continuum. Modem, highly improved varieties (“Upland cotton”), which currently account for about 90% of world cotton commerce, are day-length neutral annuals derived from subtropical, perennial antecedents. To assess levels and patterns of genetic variation in the species and to elucidate the origin of Upland cotton, 538 accessions representing the full spectrum of morphological and geographical diversity were analyzed forallozyme variation at 50 loci. Levels of variation are modest overall but are low in Upland cotton. Relationships among accessions reflect pre-Columbian influences of aboriginal peoples and later European colonists superimposed on the preagricultural pattern. In contrast to expectations, two centers of diversity are evident, one in southern Mexico-Guatemala and the other in the Caribbean. Introgression of G. barbadense genes into G. hirsutum has been common in a broad area of sympatry in the Caribbean. The germplasm of present cultivars traces to Mexican highland stocks, which, in turn, were derived from material originally from southern Mexico and Guatemala. Despite the widespread belief that germplasm from several other species has been incorporated into modem Upland stocks through intentional breeding efforts, the 50 Upland cultivars examined contain no unique alleles, suggesting that retention of genes from transspecific sources has been minimal. The most recent infraspecific treatment, which recognizes seven races, does not adequately represent genetic relationships.     

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; )     

EFFECTS OF AUXIN ON CELL ENLARGEMENT IN FERN GAMETOPHYTES: DEVELOPMENTAL STAGE OF THE CELL AND RESPONSE TO AUXIN

When gametophytes of Onoclea sensibilis are placed on an auxin-containing medium in darkness, the cells of the plant increase in length and width. Measurements were made to determine the effects of cell age and auxin concentration on the magnitude of the cells’ response. When comparing final size with size before auxin treatment, the youngest cells have the greatest response. However, they also have the greatest endogenous growth. The optimum auxin concentration for increase in length changes with the age of the cells. The greatest length is attained in young cells with an auxin concentration of 10^−-6–10^−-7 m; 10^−-5 m auxin is supraoptimal. The greatest increase in width of the cells is produced by 10^−-5 m auxin, regardless of cell age. The data are believed best to be interpreted as showing an age-dependent change in the capacity of the cells to respond to auxin.     

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.     

陆地棉花药愈伤组织的诱导和继代培养

花药培养是自６０年代以来发展起来的一项生物技术,旨在诱导出单倍体花粉植株,应用于育种实践和基础研究〔１〕。以单倍体植株为基础的单倍体育种被认为在以下几个方面具有优越性：第一,缩短育种年限;第二,排除杂种优势对后代选择的干扰〔２,３〕。此外,花药培养在...     

THE EFFECT OF BORON DEFICIENCY ON CALLOSE FORMATION AND 14C TRANSLOCATION IN BEAN (PHASEOLUS VULGARIS L.) AND COTTON (GOSSYPIUM HIRSUTUM L.)

Callose accumulated in the tissues of boron deficient bean and cotton plants, the extent and distribution of which depended on the species. Sieve plates in the phloem of boron deficient bean were characterized by heavy plugs of callose, while the sieve plates of boron deficient cotton were essentially unaffected. Translocation of ¹⁴C was, however, drastically reduced in both plants. It is suggested that callose deposition in boron deficient plants is a secondary effect of cellular damage.     

AN ULTRASTRUCTURAL STUDY OF THE RELATIONSHIP BETWEEN MICROTUBULES AND MICROFIBRILS IN COTTON (GOSSYPIUM HIRSUTUM L.) CELL WALL REVERSALS

The arrangement of cellulosic fibrils in the cell walls of cotton fibers is very unusual; rather than exhibiting a continuous spiraling in one direction, they intermittantly reverse their gyre. Microtubules that line the periphery of the protoplasm, subjacent to the plasmalemma, tend to parallel the deployment of the cell wall microfibrils. It was not known whether this parallelism persisted through the reversal. By studying tangential sections of the cell wall/protoplasmic interfaces at the reversals, we show that congruity continues even through the reversals. Colchicine treatment did not appear to inhibit cellulose synthesis but it did abolish microtubules in the cotton fiber cells and deranged normal cell wall microfibrillar orientation. Previously, cotton fibers have been shown to possess most of the familiar organelles, but we found two new features not reported heretofore. They are microfilaments and peculiar “polygonal structures” that appear to be associated with the plasma membrane.     

陆地棉珠孔的结构及花粉管在其中的生长途径

在大多数被子植物中,花粉管经珠孔进入胚珠进而实现受精,但珠孔结构及花粉管在其中的生长途径是植物受精生物学研究中较薄弱的一个环节。迄今仅在向日葵中从超微结构水平上作了详细的研究［１］,因而需要扩大研究的对象。陆地棉花粉管生长所经雌蕊组织中,关于柱头、花柱［２,３］、珠心［４,５］和助细胞［６］的超微结构已有较详细的研究,但涉及珠孔这一环节,只有简单的描述［７］。本文报道我们在这方面的研究结果。材料和方法取陆地棉（ＧｏｓｓｙｐｉｕｍｈｉｒｓｕｔｕｍＬ．）授粉前和授粉后２２小时的胚珠,切除其合点端部分…     

COTYLEDON PHOTOSYNTHESIS DURING SEEDLING GROWTH OF COTTON,GOSSYPIUM HIRSUTUM L.

Respiration and net photosynthetic O₂ production by cotton cotyledons were determined from an early age through the senescent stage. Various treatments were applied to cotyledons to assess the importance of current photosynthesis as compared to translocation of reserves to seedling development. Rates of respiration and net photosynthesis per cm² were high on 1-day-old cotyledons, but the rates decreased sharply with rapid expansion to reach a fairly stable rate. Respiration per cotyledon decreased linearly with age until the onset of senescence, then exhibited a distinct climacteric rise followed by a sharp decrease. Net photosynthesis per cotyledon increased until expansion was completed and then decreased linearly and steeply with age. Excision of cotyledons, inhibition of photosynthesis either chemically or by covering, and removal of the terminal bud indicated that current photosynthesis is a potent force behind early epicotyl growth.     

棉花花粉发育过程中同工酶和蛋白质的研究

利用超薄胶电泳技术对陆地棉花粉发育各期的酯酶和过氧化物酶的同工酶以及蛋白质的种类及活性变化进行研究。结果发现：在花粉第一次有丝分裂结束之前,存在大量的低分子量酯酶和过氧化物酸酶,花粉成熟后又新出现一些大分子量酯酶和过氧化物酶在花粉第一次有线四分体阶段,了一种特异蛋白,推测具有调控作用。在有丝分裂结束后,出现了一些新的蛋白质,这些蛋白质存在的时间很短。之后大量蛋白质开始合成,并在数量和种类上有逐渐增     

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; )     

陆地棉胚性愈伤组织的变异及高频胚胎发生

陆地棉（Ｇｏｓｓｙｐｉｕｍ ｈｉｒｓｕｔｕｍ Ｌ．）胚性愈伤组织在两年多的继代培养过程中,由淡绿或灰色疏松状转变成灰黄色致密团块状,胚胎发生能力经历了一个由低到高再到低的过程。培养两年半后,从中分离出３种不同的愈伤组织系。第一种可产生大量的胚状体;第二种可产生少量胚状体;而第三种失去了胚胎发生能力。第一种团块颗粒小,后两种团块颗粒大。通过选择培养第一种愈伤组织系,建立了３ 个陆地棉栽培品种的高频体细胞胚胎发生系。染色体观察显示：其变异频率随愈伤组织培养代数的增加而升高;３ 种不同的愈伤组织系中,二倍体细胞的频率大小依次为：第一种＞ 第二种＞ 第三种。此外,第一种含有较多的超二倍体细胞,而后两种含较多亚二倍体细胞