THE DEPENDENCE OF CELL DIVISION IN CHLORELLA ON TEMPERATURE AND LIGHT INTENSITY

The effects of temperature and light on cell division were studied in synchronized suspensions of the high-temperature strain Chlorella 7–11–05. It was found that the time for incipient cell division, the progress in the process after it started, and the number of cells produced are influenced by temperature and light intensity. Within limits, cell division is generally favored by the increase in temperature. The increase in light intensity first favors cell division then, after the optimal light intensity is attained, a further increase in light intensity inhibits cell division. Observations are discussed in connection with the findings of other investigators. The limitations of cell division by temperature and light intensity are considered to be separate from the effects of these factors on growth.     

NaHSO3-Na2SO3混合液对大麦幼苗生长和细胞分裂的影响

 研究SO2在生物体内的衍生物——亚硫酸氢钠和亚硫酸钠混合液（1：3, mol·L-1）(以下简称亚硫酸氢钠)对大麦(Hordeum vulgare)幼苗生长发育和根尖细胞分裂的效应。幼苗生长发育依赖于亚硫酸氢钠的浓度和接触时间,在一定浓度范围内,大麦幼苗的高度和根系发育与处理时间之间具有正的线性相关;幼苗高度、根长、根系体积和干重与处理浓度之间具有负的线性相关。高浓度亚硫酸氢钠短时间处理或低浓度长时间处理,能导致根尖细胞有丝分裂指数下降,并使根尖中具有微核的细胞明显增多,部分细胞核发生固缩。在0.1～5.     

THE EFFECT OF 5-BROMODEOXYURIDINE ON DNA REPLICATION AND CELL DIVISION IN TETRAHYMENA PYRIFORMIS

Populations of Tetrahymena pyriformis were grown in a chemically defined medium containing the thymidine analogue 5-bromodeoxyuridine (BUdR). About 65% of the thymidine sites in DNA were substituted by BUdR. During the first generation in the presence of BUdR, all DNA became hybrid. After the following cell division, in about 80% of the cells the second DNA replication round was initiated but no further cell division took place. The cells could be rescued by removing BUdR and adding thymidine. New replication took place before the first cell division. However, although the cells contained double heavy as well as hybrid DNA, only the hybrid DNA was replicated. After a full replication of the hybrid DNA, normal growth was restored. Melting profiles of normal, hybrid, and double heavy DNA indicated a structural change of the double heavy DNA.     

THE EFFECT OF AUXIN AND GUANINE ON CELL EXPANSION AND CELL DIVISION IN THE GAMETOPHYTE OF THE FERN,ONOCLEA SENSIBILIS

Miller , J. H. (Yale U., New Haven, Conn.) The effect of auxin and guanine on cell expansion and cell division in the gametophyte of the fern, Onoclea sensibilis. Amer. Jour. Bot. 48(9): 816–819. Illus. 1961.—Auxin and guanine promote cell expansion in 0. sensibilis gametophytes. The optimum concentration of auxin for total expansion is 10^−-5 M, but the optimum for elongation is 10^−-6 M. Above this concentration the cells expanded isodiametrically. Guanine is active at higher concentrations than auxin. Increasing concentrations of auxin progressively inhibit red light-induced cell division, while guanine has no effect on cell division. Neither kinetin nor adenine promotes cell expansion or cell division.     

高温胁迫对桃和抽细胞膜透性和光合色素的影响

研究了桃和柚离体叶片在高温胁迫下细胞膜透性（电解质渗漏和Ｐｉ渗漏）和光合色素的变化及其与抗热性的关系。结果表明。（１）高温处理下,无论是黑暗条件下浸水２４ｈ,还是光照条件下浸水２４ｈ,两种果树的电解质和Ｐｉ渗漏都显著增加,光照有利于膜的修复;（２）高温引起Ｃｈｌ含量下降,Ｃｈｌａ／ｂ比值上升;（３）上述这些生理反应与果树的抗热性有关,可用于果树的抗热性鉴定。     

高温胁迫对桃和抽细胞膜透性和光合色素的影响

研究了桃和袖离休叶片在高温胁迫下细胞膜透性（电解质渗漏和Pi渗漏）和光合色素的变化及其与抗热性的关系。结果表明。①高温处理下,无论是黑暗条件下浸水24h,还是光照条件下浸水24h,两种果树的电解质和Pi渗漏都显著增加,光照有利于膜的修复;②高温引起Chl含量下降,Chla／b比值上升;③上述这些生理反应与果树的抗热性有关,可用于果树的抗热性鉴定。     

EFFECTS OF TEMPERATURE AND ILLUMINANCE ON CELL DIVISION RATES OF THREE SPECIES OF TROPICAL OCEANIC PHYTOPLANKTON1

Three species of tropical oceanic phytoplankton were isolated from two locations in the eastern Pacific Ocean. Unialgal cultures were maintained in an enriched seawater medium. The effects of temperature, and, in separate experiments, illuminance, on the exponential cell division rates of those algae were investigated. For 2 isolates of Gymnodinium sp. (probably G. simplex), maximum growth rates were 1.25 and 1.7 divisions/24 hr, the optimum temperature range was 23–29 C, the compensation illuminance was 35 ft-c, and the saturation illuminance was 750 ft-c and above. For a small species of Chaetoceros, the maximum growth rate was 6.0 divisions/24 hr, the optimum temperature range was 23–37 C, the compensation illuminance was 10 ft-c, and the saturation illuminance was 600 ft-c. For a small Nannochloris species, the maximum growth rate was 4.5 divisions/ 24 hr, the optimum temperature range was 27–37 C, and the saturation illuminance was 800 ft-c. Nannochloris grew heterotrophically by apparently utilizing organic matter supplied by soil extract.     

X射线对根尖细胞分裂和分化的作用

用30—70GyX射线照射小麦幼苗(浸种后5天)后发现根毛区到根尖的距离缩短,根毛变密,根毛长度为对照的2—3倍。照射后2—3天就可看到该现象。根毛着生处到根尖的距离随剂量增加而减少,甚至根尖全为根毛所复盖,另外还看到有分叉的根毛。根尖纵切片表明根尖分生区随剂量增加而缩小,分生区后接着就出现输导组织。玉米和黄瓜也有类似现象。这现象说明根细胞的分裂过程对射线很敏感,而分化过程则相当耐辐射,细胞分裂停止后立即转向细胞分化过程。     

低氧对新生大鼠脾单个核细胞DNA合成及转化的影响

本研究以荧光法测定脾单个核细胞ＤＮＡ合成及ＭＴＴ比色法测定的脾单个核细胞对ＣｏｎＡ的增殖反应,观察模拟高原低氧对出生后１４天大鼠上述两指标的影响,同时也观察了交感神经和副交感神经的活动状态,以初步探讨低氧对上述两指标的作用是如何介导的。结果表明：５ｋｍ海拔高度低氧作用２４ｈ不抑制脾单个细胞ＤＮＡ合成及脾单个核细胞转化,而作用５天时则抑制ＤＮＡ合成及脾单个核细胞转化,分别为对照组的５６．６％（Ｐ＜０．０１）和８６．８％（Ｐ＜０．０５）;７ｋｍ海拔高度低氧作用２４ｈ,ＤＮＡ合成及脾单个核细胞转化均受抑制,分别为对照组的６１．０％（Ｐ＜０．０１）和８１．２％（Ｐ＜０．０１）;７ｋｍ海拔２４ｈ低氧导致脾脏中乙酰胆碱下降,儿茶酚胺升高;用ＤＳＰ－４中枢药理性损毁ＮＥ神经元,可使脾单个核细胞ＤＮＡ合成的抑制程度减弱,脾脏中儿茶酚胺含量下降。这些结果表明低氧可抑制新生大鼠脾单个核细胞的ＤＮＡ合成及转化,并可能与交感神经兴奋及副交感神经抑制有关     

EFFECTS OF TEMPERATURE AND ILLUMINANCE ON CELL DIVISION RATES OF THREE SPECIES OF TROPICAL OCEANIC PHYTOPLANKTON1

Three species of tropical oceanic phytoplankton were isolated from two locations in the eastern Pacific Ocean. Unialgal cultures were maintained in an enriched seawater medium. The effects of temperature, and, in separate experiments, illuminance, on the exponential cell division rates of those algae were investigated. For 2 isolates of Gymnoclinium sp. (probably G. simplex), maximum growth rates were 1.25 and 1.7 divisions/24 hr, the optimum temperature range was 23-29 C, the compensation illuminance was 35 ft-c, and the saturation illuminance was 750 ft-c and above. For a small species of Chaetoceros, the maximum growth rate was 6.0 divisions/24 hr, the optimum temperature range was 23-37 C, the compensation illuminance was 10 ft-c, and the saturation illuminance was 600 ft-c. For a small Nannochloris species, the maximum growth rate was 4.5 divisions/ 24 hr, the optimum temperature range was 27-37 C, and the saturation illuminance was 800 ft-c. Nannochloris grew heterotrophically by apparently utilizing organic matter supplied by soil extract.