SHOOT GROWTH AND HISTOGENESIS OF TREES POSSESSING DIVERSE PATTERNS OF SHOOT DEVELOPMENT

Shoot growth and histogenesis were followed in five unrelated tree taxa possessing inherently diverse patterns of shoot development. Following the resumption of growth in spring, each species differs quantitatively in the number of internodes elongating contemporaneously, in rates and duration of internodal elongation and seasonal periodicity of shoot growth. The basic pattern of internode elongation and histogenesis is qualitatively similar in each of the dicotyledonous species observed irrespective of growth habit or final form of the shoot produced. During the intial phase of internode development, growth is essentially uniform throughout young internodes, corresponding to an active period of cell division during which time pith cells increase in size to about one-third their final length. Subsequently, the pattern of cell division shifts progressively upward concomitant with increased elongation and maturation of pith cells in the basal portion of developing internodes. Thereafter, a wave of cell division accompanied by cell elongation continues to proceed acropetally until growth finally ceases in the distal portion of each internode. As long as internode elongation continues, frequently at distances 15–20 cm below the shoot apex, cell divisions still occur in the distal growing portion. As successive portions of each internode mature acropetally, final length of pith cells becomes relatively uniform throughout the internode. During the process of internode growth and development, cell lengths increase only two- to threefold, whereas cell numbers increase ten- to 30-fold, indicating the dominant role of cell division and increases in cell number to final internode length. Morphological patterns of shoot expression associated with differences in internode lengths along the axis of either preformed or neoformed shoots, as well as sylleptic branches, are due to differences in cell number rather than final cell length. Significant variations in final internode lengths along the axis of episodic shoots, caused by either endogenous or exogenous factors, are also attributed to differences in cell number.     

水分胁迫下盆栽冬小麦根系生长与苗系生长及某些生理特性的关系

水分胁迫下,盆栽冬小麦根干重和根长密度呈直线正相关。鉴于根长密度反映了土壤中根系最活跃的部分［５］,是研究植物根系吸收水分和养分的最优参数之一［６］,本文用之研究了它与地上部生物量、净同化速率、叶水势和叶片相对含水量、气孔阻力和蒸腾速率的关系。结果表明,根长密度与净同化速率和地上部干重呈直线负相关,与叶水势和叶片相对含水量呈直线正相关;与气孔阻力呈直线负相关,与蒸腾速率呈直线正相关。为实验室进行冬小麦生长控制与生理特性控制提供了一定的基础。     

RELATIONSHIPS BETWEEN GROWTH RATES AND NUCLEIC ACID CONTENTS IN THE ROOTS OF INBRED LINES OF CORN

Woodstock , Lowell W., and Folke Skooc . (U. Wisconsin, Madison.) Relationships between growth rates and nucleic acid contents in the roots of inbred lines of corn. Amer. Jour. Bot. 47(9) : 713–716. Illus. 1960.—A study has been made of the rates of elongation and nucleic acid contents of the roots of inbred lines of Zea mays, var. W-158, A-374B, W-58, W-28, 8A, and W-148. A direct proportionality was found between the ribosenucleic acid contents (μg./root) of the apical 3 or 6 mm. of the roots (roughly equivalent to their growing tips) and their rates of elongation. This strict, quantitative relationship to growth rate appears to be specific for RNA; it was not found for DNA, and it was independent of the size of the root. A detailed study of one line (W-58) has shown, furthermore, that the ribosenucleic acid content in the root tip decreases with time in proportion to the decrease in the growth rate of the root.     

GROWTH PERIODICITY AND THE SHOOT TIP OF ABIES CONCOLOR

Parke , Robert V. (Colorado State U., Fort Collins.) Growth periodicity and the shoot tip of Abies concolor. Amer. Jour. Bot. 46(2) : 110-118. Illus. 1959.—The terminal shoot of Abies concolor shows a marked seasonal activity or growth periodicity of the meristmatic regions. Hence, the annual developmental sequence may be divided into three growth phases: the rest phase, during which the fully formed telescoped shoot remains in a state of suspended growth; the first growth phase, during which the telescoped shoot elongates rapidly and gives rise to numerous cataphylls; and, the second growth phase, during which shoot elongation is completed and a new unelongated axis bearing many needle primordia is formed. The shoot tip of Abies consists of 4 clearly definable cytohistological zones; the apical initials, the sub-terminal mother cells, the peripheral zone, and the zone of central tissue. The shape of the shoot tip and the volume of its various cytohistological zones change markedly during the annual growth sequence, but the basic zonation pattern remains the same.     

REGULATION OF CHAMISE SHOOT GROWTH

Nutritional, hormonal, and environmental control of chamise (Adenostoma fasciculatum H. & A.) shoot growth was investigated. In vitro culture of shoot tips demonstrated that 0.18 M sucrose was required for optimum apical growth. Cytokinin (benzyladenine) promoted shoot growth at otherwise growth-limiting sucrose concentrations and induced uptake of sucrose from the basal medium. Abscisic acid inhibited growth of cultured shoot tips induced by high sucrose concentration or cytokinin. In the field, inhibition of shoot growth was a function of water stress. These studies indicate that the effects of water stress on chamise shoot growth may be mediated by changes in carbohydrate, cytokinin, or growth inhibitor levels at the shoot apex.     

扬子毛茛和石龙芮的核型研究

报道了浙江省常见的２种毛茛属植物－扬子毛茛和石龙芮的染色体资料,扬子毛茛体细胞染色体数目２ｎ＝３２,核型组成;Ｋ（２ｎ）＝４ｘ＝３２＝１６ｍ＋８ｓｍ＋８ｓｔ。石龙芮体细胞染色体数目２ｎ＝３２,核型组成;Ｋ（２ｎ）＝４ｘ＝３２＝８ｍ＋２４ｓｍ。     

陕南地区油橄榄生长发育与生态条件关系的研究

根据定位观测和实地调查资料研究了油橄榄在陕南地区的生长发育和环境条件的关系,油橄榄树的枝条日高生长量为昼夜生长类型。夜间生长高于昼间的１２１％－１６０％;６、７、８、９月的生长量占全年生长量的７６％。油橄榄树的年生长量和产量状况与土壤含水量和土壤质地性质有密切关系;油橄榄树为阳性树种,在增加光照的环境条件下生长和结实良好,反之较差。     

步氏巨猿犬齿与前臼齿咬合关系的观察

步氏巨猿的上犬齿与下第一前臼齿的咬合关系有两种主要类型:一是相似于“猿类”的,另一相似于“人类”的。前者为雄性个体所具有,后者为雌性个体所具有。另有少数个体的则是中间类型。上犬齿与下第一前臼齿的咬合特征的分类学上的意义是可疑的。至少就绝大部分雄性步氏巨猿个体来说,很难认为其犬齿是参与臼齿的功能。步氏巨猿下第一前臼齿之所以呈双尖类型,与其犬齿并无直接的关系。     

RELATION OF PLASTOCHRON TO ANATOMY AND GROWTH IN THE SHOOT APEX OF CHRYSANTHEMUM

The relation between plastochron stage, apical anatomy, and thymidine-C¹⁴ incorporation was studied in the shoot apex of Chrysanthemum morifolium ‘Albatross.’ Apices were sorted into early, middle, and late plastochron stage under a dissecting microscope, fixed, and sectioned longitudinally so that median sections included known sectors of the apical flank. Study of these sections revealed no discernible difference between apices in early, middle, or late plastochron with respect to regularity of cell pattern, presence of a cambium-like zone, appearance of the second tunica layer or staining pattern with pyronin or with toluidine blue. Likewise, apices that had been treated with thymidine-C¹⁴ for 2-4 hr showed no differences between the three stages in number or distribution of labeled cells.