THE LIGHT GROWTH RESPONSE AND THE GROWTH SYSTEM OF PHYCOMYCES

1. The Roscoe-Bunsen law holds for the light growth response of Phycomyces if the time component of stimulation is short. With exposures longer than a few seconds, the reaction time to light is determined by the intensity and not by the energy of the flash. 2. The possible nature of the very long latency in the response to light is considered in terms of the structure of the cell and its mechanism of growth. It is suggested that during the latency some substance produced by light in the protoplasm is transported centrifugally to the cell wall or outermost layer of protoplasm. 3. The total elongation occurring over a period of 1 to 2 hours is independent of flashes of light or temporary darkening. Light acts by facilitating some change already under way in the growth system, and during the principal phase of elongation is not a necessary or limiting factor for growth. 4. Judged by the reaction time, the original sensitivity is restored in the light system following exposure to light in about one-third the time required for equilibrium to be reattained in the growth system.     

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 GROWTH OF BACTERIOPHAGE AND LYSIS OF THE HOST

1. A new strain of B. coli and of phage active against it is described, and the relation between phage growth and lysis has been studied. It has been found that the phage can lyse these bacteria in two distinct ways, which have been designated lysis from within and lysis from without. 2. Lysis from within is caused by infection of a bacterium by a single phage particle and multiplication of this particle up to a threshold value. The cell contents are then liberated into solution without deformation of the cell wall. 3. Lysis from without is caused by adsorption of phage above a threshold value. The cell contents are liberated by a distension and destruction of the cell wall. The adsorbed phage is not retrieved upon lysis. No new phage is formed. 4. The maximum yield of phage in a lysis from within is equal to the adsorption capacity. 5. Liberation of phage from a culture in which the bacteria have been singly infected proceeds at a constant rate, after the lapse of a minimum latent period, until all the infected bacteria are lysed. 6. If the bacteria are originally not highly in excess, this liberation is soon counterbalanced by multiple adsorption of the liberated phage to bacteria that are already infected. This leads to a reduction of the final yield.     

THE GROWTH AND RESPIRATION OF THE AVENA COLEOPTILE

1. Transport of the plant growth hormone into the Avena coleoptile as well as the action of the hormone on cell elongation in the coleoptile are shown to depend upon aerobic metabolism. 2. Crystalline auxine, in contrast with impure preparations, affects neither the magnitude nor the respiratory quotient of coleoptile respiration. 3. Increasing age of the coleoptile cell decreases its rate of elongation much more than its rate of respiration. HCN or phenylurethane on the other hand decrease the two processes to the same extent, in spite of the fact that only a small portion of the energy liberated by respiration can be used in the mechanical process of growth. 4. From 2 and 3 it is concluded that processes of a respiratory nature but of relatively small magnitude form one or more integral steps in the chain of reactions by which the plant growth hormone brings about cell elongation.     

THE RATE OF GROWTH OF THE DAIRY COW : IV. GROWTH AND SENESCENCE AS MEASURED BY THE RISE AND FALL OF MILK SECRETION WITH AGE.

Data are presented on the effect of age on milk secretion in the dairy cow. From the age when milk secretion usually begins (2 years) to the age when maximum body weight is reached (about 8 years) increase of milk secretion and increase of body weight with age follow the same exponential course, which is the course of a monomolecular reaction of chemistry. After this age, unlike body weight which remains practically constant, milk secretion declines exponentially, that is, the course of decline follows the course of decline of a monomolecular reaction. The whole course of milk secretion with age was therefore found to follow approximately the course of two simultaneous, consecutive, monomolecular reactions. This is taken to mean that growth and senescence go on simultaneously from the beginning to the end of life, and that each follows an exponential law with age; and therefore perhaps that the course of the two processes are limited by two consecutive chemical reactions.     

THE GROWTH AND NUTRITION OF THE AFRICAN ELEPHANT

In order to gain information on the growth and nutrition of two populations of elephants in Murchison Falls National Park, Uganda, their urinary excretions of hydroxyproline peptides (HP) were compared. Animals from the “south bank” population had a consistently higher level of excretion than corresponding animals from the “north bank” population. This indicated a faster rate of growth and a superior nutritional status in “south bank” animals at the time of sampling. The HP output from both populations was found to run parallel to the seasonal variation in rainfall and vegetation growth. Sampling from each population was carried out at a different time of the year and evidence is presented to show that the differences in the rate of growth are a direct result of this. It is concluded that any primary differences between the populations are small enough to be obliterated by seasonal changes. The effect of the seasons on the growth of the elephant is therefore examined in more detail, and a direct influence on collagen metabolism is discussed.     

鹅掌楸属植物的多糖壁前体和花粉管的生长

本文观察描述了中国鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎｃｈｉｎｅｎｓｅ）和北美鹅掌楸（Ｌ．ｔｕｌｉｐｉｆｅｒａ）花粉在异已柱头萌发和花粉管生长期间多糖壁前体的发生、形态结构和生理功能．１、多糖壁前体在形态上有Ｐ－粒子（Ｐｏｌｙｓａｃｃｈａｒｉｄｅｐａｒｔｉｃｌｅｓ）,被膜小泡（ｃｏａｔｅｄｖｅｓｉｃｌｅ）和小泡（ｖｅｓｉｃｌｅ）三种。２、Ｐ－粒子于单核花粉期已经发生,至花粉管延伸期为发生高峰。多糖壁前体是在高尔基体,内质网和线粒体的相继、连续作用下,由淀粉质体、蛋白体和脂滴降解形成．３、Ｐ－粒子的形态随不同发育时期而变化,早期为成群的电子透明小泡,或为蛋白质束缚的挤压成多面体形,后期为内含颗粒或微纤丝的无被膜粒子或具刺被膜粒子。４、Ｐ－粒子移至管端．或融合或单个通过周质内质网（ＣＥＲ）,释放内容物参与管端壁的形成,被膜小池和小泡移至花粉管次顶端区向质膜外分泌,参与花粉管壁内层的形成,或移至管端,提供膜片。最后讨论了亲和性与超微结构特征的关系．     

THE RATE OF GROWTH OF THE DAIRY COW : III. THE RELATION BETWEEN GROWTH IN WEIGHT AND INCREASE OF MILK SECRETION WITH AGE.

It is shown that from 2 years, the age when milk secretion usually begins, to 9 years, the age of maximum body weight, the increase of milk secretion with age follows the course of growth in body weight— both can be accurately represented by the equation of a monomolecular chemical reaction having a velocity constant of approximately the same numerical value. While increase in milk secretion and increase in body weight with age follow the same course, it is shown that increasing body weight contributes only about 20 per cent to increasing milk secretion with age. The fact that milk secretion and body weight follow the same course, even though they are largely independent of each other indicates that increase in body weight is a good measure of growth of the dairy cow; this fact also shows that the increase of milk secretion with age may be used as a measure of growth. The fact that milk secretion, like body weight, follows the course of a chemical reaction, adds further support to the theory that growth is limited by a chemical reaction.     

鱼类生长和生长激素分泌活动的调节（综述）

本文综述近十年来在鱼类生长激素分泌和鱼体生长的神经内分泌调节方面取得的研究进展,阐明脑（各种神经内分泌因子）－脑垂体（分泌生长激素）－肝脏（产生类胰岛素生长因子）轴调控鱼类生长的作用,并在此理论基础上提出可供养鱼生产实践应用的基本途径。     

GROWTH AND ORGANIZED DEVELOPMENT OF CULTURED CELLS IV. THE BEHAVIOR OF THE NUCLEUS

Mitra , J., Marion O. Mapes , and F. C. Steward . (Cornell U., Ithaca, New York.) Growth and organized development of cultured cells. IV. The behavior of the nucleus. Amer. Jour. Bot. 47(5) : 357—368. Illus. 1960.–The nuclei and the chromosomes of carrot cells have been examined at various stages throughout the following sequence: (1) growth of a tissue culture from a preformed explant of secondary phloem from the carrot root; (2) growth and multiplication of carrot cells freely suspended in a liquid medium; (3) growth and re-formation of organs (roots) and whole plants (including flowers) from cells in the freely suspended state. The cells of the carrot are normally diploid (2n = 18), the cells which develop in the explant are also diploid, and the cells of the re-formed organs, and even the flowers developed upon plants grown from cells, are also normal and diploid; normal meioses also occur. Nevertheless, the wide range in growth and form of the freely suspended cells is accompanied by a rich diversity of cytological conditions; these include tetraploid and highly polyploid nuclei which divide, haploidy and such chromosomal aberrations as di- and even tri-centric bridges. Two division figures showing chromosome numbers at different levels of ploidy were seen within the confines of one large cell, and, in another, 2 adjacent division figures were observed with chromosome numbers lower than diploid. Small thick-walled, densely protoplasmic cells divide to form bi- and tetra-nucleate conditions, and in a giant cell a highly multinucleate condition has been seen. Despite this, however, all the regenerated roots and plants yet examined are normally diploid. The implications of these events are discussed.