THE MECHANISMS OF TROPISTIC REACTIONS AND THE STRYCHNINE EFFECT IN DAPHNIA

1. Experiments with strychnine were performed to test two assumptions important in the development of a theory for the mechanisms involved in the tropisms exhibited by Daphnia. 2. After a brief interval in strychnine solution Daphnia exhibits a reversal of the primary sign (a) of phototropism, from negative to positive; and (b) of galvanotropism, from anodic to cathodic. In both cases the orientation of the body remains the same. 3. The mechanism responsible for the sign of phototropism and galvanotropism in Daphnia is therefore distinct from that underlying orientation. 4. Evidence is obtained indicating that changes in sign of tropism, produced by changes in illumination or by subjection to strychnine, involve the control of antagonistic muscles in the swimming appendages which are reciprocally innervated.     

THE EFFECT OF WAVELENGTH AND INTENSITY OF LIGHT ON THE PROPORTION OF PIGMENTS IN PORPHYRIDIUM CRUENTUM

Brody , Marcia , and Robert Emerson . (U. Illinois, Urbana.) The effect of wavelength and intensity of light on the proportion of pigments in Porphyridium cruentum. Amer. Jour. Bot. 46(6): 433–440. Illus. 1959.—We specify a medium for Porphyridium cruentum made from distilled water and inorganic salts, without addition of earth extract, sea water or other supplements of uncertain composition, which sustains excellent growth through successive transfers. By control of intensity and wavelength of light used for growing the cultures, we have found it possible to vary the concentrations of chlorophyll and phycoerythrin, and also the proportions of these 2 pigments, over a considerable range. The changes in proportion of red and green pigments, in response to culturing in green and in blue light, are opposite to the changes that would be predicted from Engelmann's theory of complementary chromatic adaptation, when the intensities of the blue and green light are of the order of 10⁴ ergs/cm²/sec. (or greater). However, at about 1/100 of this intensity, the changes are in the direction of complementary chromatic adaptation.     

DIGESTION AND THE DISTRIBUTION OF ACID PHOSPHATASE IN BLEPHARISMA

Suspensions of Blepharisma intermedium were fed latex particles for 5 min and then were separated from the particles by filtration. Samples were fixed at intervals after separation and incubated to demonstrate acid phosphatase activity. They were subsequently embedded and sectioned for electron microscopy. During formation of the food vacuole, the vacuolar membrane is acid phosphatase-negative. Within 5 min, dumbbell-shaped acid phosphatase-positive bodies, possibly derived from the the acid phosphatase-positive Golgi apparatus, apparently fuse with the food vacuole and render it acid phosphatase-positive. A larger type of acid phosphatase-positive, vacuolated body may also fuse with the food vacuole at later stages. At about 20 min after formation, acid phosphatase-positive secondary pinocytotic vesicles pinch off from the food vacuoles and approach a separate system of membrane-bounded spaces. By 1 hr after formation, the food vacuole becomes acid phosphatase-negative, and the undigested latex particles are voided into the membrane-bounded spaces. The membrane-bounded spaces are closely associated with the food vacuole at all stages of digestion and are generally acid phosphatase-negative. Within the membrane-bounded spaces, dense, pleomorphic, granular bodies are found, in which are embedded mitochondria, paraglycogen granules, membrane-limited acid phosphatase-containing structures, and Golgi apparatuses. The granular bodies may serve as vehicles for the transport of organelles through the extensive, ramifying membrane-bounded spaces.     

THE EFFECT OF LIGHT INTENSITY AND TEMPERATURE ON PLANT GROWTH AND CHLOROPLAST ULTRASTRUCTURE IN SOYBEAN

Soybean plants grown in controlled environment cabinets under light intensities of 220 w/m² or 90 w/m² (400–700 nm) and day to night temperatures of 27.5–22.5 C or 20.0–12.5 C in all combinations, exhibited differences in growth rate, leaf anatomy, chloroplast ultrastructure, and leaf starch, chlorophyll, and chloroplast lipid contents. Leaves grown under the lower light intensity at both temperatures had palisade mesophyll chloroplasts containing well-formed grana. The corresponding leaves developed under the higher light intensity had very rudimentary grana. Chloroplasts from high temperature and high light had grana consisting of two or three appressed thylakoids, while grana from the low temperature were confined to occasional thylakoid overlap. Spongy mesophyll chloroplasts were less sensitive to growth conditions. Transfer experiments showed that the ultrastructure of chloroplasts from mature leaves could be modified by changing the conditions, though the effect was less marked than when the leaf was growing.     

光和暗条件下低温对黄瓜和水稻叶绿素蛋白质复合体的影响

本试验以黄瓜和水稻幼苗为材料,研究了光照和黑暗条件下低温对植物叶绿素蛋白质复合体的影响。SDS—PAGE电泳结果表明:5℃及12h 280μmol m~(-2)S~(-1)处理2d,Chl-蛋白质复合体的降解明显大于5℃暗低温处理;低温与光照对P700-CPa_1的影响大于LHCP。叶绿素荧光测定表明;5℃及12h 280μmol m~(-2)s~(-1)的处理对PSⅡ的影响亦大于暗低温处理。由此认为:低温与光对植物叶绿体的PSⅠ和PSⅡ都有明显的影响,其机理可能与常温下高光强引起的光抑制相类似;不同的是低温下中等光强就能引起光抑制。因此,在光照低温下往往加剧植物冷害的发生。     

THE EFFECT OF LIGHT INTENSITY AND SUCROSE FEEDING ON THE FINE STRUCTURE IN CHLOROPLASTS AND ON THE CHLOROPHYLL CONTENT OF ETIOLATED LEAVES

Changes in the fine structure of proplastids of etiolated leaves exposed to various conditions of light and darkness for 24 and 48 hours were investigated, and the chlorophyll content of the leaves so treated was determined in vivo. The light treatments were given while the leaves were floated on tap water or on a 0.2 M sucrose solution. Leaves floated on water under low light intensity (2 foot-candles) were low in chlorophyll and contained plastids with concentric rows of vesicles. Transferring the leaves back to darkness resulted in the disappearance of the concentric rigs and re-formation of vesicular centers together with straight rows of vesicles and tubules, evenly spaced throughout the stroma. Chloroplasts of leaves floated on a sucrose solution under low light showed large vesicular centers together with stacks of rows of elongated tubules. The same chloroplast structure was found in leaves floated on a sucrose solution in the dark, after having been exposed to weak light for 24 hours. Chlorophyll content in these leaves was the same as in leaves floated on water under high light intensity, where the chloroplasts had normal grana and lamellae. The effect of the investigated factors on plastid development is discussed.     

EFFECT OF SPECTRAL QUALITY ON GROWTH AND PIGMENTATION OF PICOCYANOBACTERIA1

The influence of spectral quality on growth and pigmentation was compared among five strains of marine and freshwater picocyanobacteria grown under the same photon flux density (28 μE · m^?2·s^?1). Growth and phycoerythrin (PE) concentration per unit carbon increased when marine Synechococcus WH7803 was grown under green light as compared to red light, but no change in phycocyanin concentration occurred. Marine Synechococcus strain 48B66 also showed greater levels of PE when grown under green light than under red light, but no concomitant growth increase occurred. Both strains thus exhibited Group II chromatic adaptation. Additionally, strain 48B66 increased the relative level of phycourobilin compared to phycoerythrobilin when grown under red light. In contrast, both marine and freshwater Synechococcus strains containing no PE showed decreased growth under green light. Chlorophyll a concentrations were greatest or among the greatest in all strains grown under green light. These results suggest that light quality, through its effects on growth rate, may be an important factor controlling the distribution and abundance of the various pigment types of Synechococcus.     

光对小麦幼叶脂氧合酶活性及膜脂过氧化作用的影响

选用抗旱型小麦品种陕合６号和水分敏感型小麦品种郑引１号的黄化幼苗为材料,研究了光处理对小麦幼叶脂氧合酶活性和膜脂氧化作用的影响。结果表明：光处理后黄叶变绿,叶片中的ＬＯＸ活性降低,丙二醛含量和叶绿素含量增加,膜透性升高,ＩＵＦＡ升高。ＬＯＸ活性与光抑制过程的恢复,光保护过程及膜脂过氧化作用有关。光诱导产生的膜脂过氧化作用是一种“准膜脂过氧化作用”。     

烟草叶组织培养中光与激素对形态发生的调节作用

我们在烟草叶的组织培养中,研究了光与激素对形态发生所起调节作用的相互关系。在培养基中细胞分裂素与生长素的浓度比例都取得最佳值,而浓度绝对值则取两组不同数值。在这两组实验条件下,分别考察了不同波段,不同强度的光照射对于不定芽的发生和愈伤组织增重的影响。用不同波段的光照射,改变光强,光促进生长的效应都有一极大值。用蓝光照射,极大值的数值最高。激素浓度低时光的效应较大;浓度高时,除蓝光外,其他波段的光效应都很微弱。     

在光照和黑暗条件下低温对水稻幼苗光合器官膜脂过氧化作用的影响

水稻幼苗在光照和黑暗的低温胁迫下(5±1℃,48h),引起叶绿体中SOD活性明显降低,膜脂过氧化产物——MDA显著积累,叶绿体超微结构发生不同程度的破坏。光照下低温处理比黑暗中低温处理变化更为显著;不同耐寒力的水稻品种之间亦表现出一定的差异。     

THE EFFECT OF LIGHT ON THE PERMEABILITY OF PARAMECIUM

1. The permeability of Paramecium to NH₄OH is greater when the cells are exposed to light than it is when they are in darkness. 2. This change can be demonstrated in cells exposed to monochromatic red light, though it is small. It becomes greater as the wave lengths shorten, and is greatest in the near ultra-violet. 3. The permeability increases as the duration of exposure to light is prolonged. 4. These experiments demonstrate the necessity of controlling the illumination when using Paramecium in physiological tests.     

THE EFFECT OF ULTRAVIOLET LIGHT ON PHOTOSYNTHESIS

1. An unidentified unit in the mechanism of the photosynthesis of Chlorella pyrenoidosa is rendered inactive by the absorption of one quantum of ultraviolet light (2537 Å wave length). 2. The same irradiation has no effect on the normal respiration of Chlorella pyrenoidosa. Experiments have not yet been made on the respiration inhibitable by HCN. 3. No chemical change was detected in the chlorophyll extracted from irradiated cells.     

THE EFFECT OF GROWTH ILLUMINATION ON THE PIGMENTATION OF A MARINE DINOFLAGELLATE12

Amphidinium klebsii cultures grown under different light intensities exhibited similar chlorophyll a content per cell. Among the accessory pigments, chlorophyll c concentration decreased slightly in cells exposed to increasing light intensities up to 0.129 ly/min. The concentration of the 2 major xanthophylls present in A. klebsii cells–peridinin and diadinoxanthin–however, varied according to the light background of the cells. Some biochemical pathways in the formation of peridinin in dinoflagellates are discussed.