FURTHER NOTES ON THE GROWTH AND CHLOROPHYLL FORMATION OF CHLORELLA PROTOTHECOIDES

1. Using area of a fixed concentration as a nitrogen source,cells of Chlorella protothecoides were grown in the presenceof various carbon compounds. Magnitudes of growth of the cellswere widely different depending on the carbon sources used;glucose and fructose being most favourable substrates and galactose,glycerol and acetate coming next. But the amounts of chlorophyllformed in the cells during the experimental period were almost,the same irrespective of the different carbon sources, withsome exceptions. The similarity of the chlorophyll level observedin these experiments seemed to indicate that the formation ofchlorophyll was limited largely by the nitrogen source but notby the carbon source. 2. Strong bleaching effect was recognized with glucose and fructoseat their high concentration, which produced totally chlorophyll-lesscells. On the other hand, a stimulating effect on chlorophyllformation was observed with galactose at the different concentrationsexamined. 3. Effects of glycine and ammonium carbonate as the nitrogensource on the algal growth and pigmentation were studied insome details. The results were similar to those previously obtainedwith urea, confirming our previous conclusion that the algalpigmentation is profoundly affected by the concentration balancebetween glucose and nitrogen source. ¹Present address: Tokyo Research Laboratories, Tanabe SeiyakuCo., Toda-machi, Saitama.     

Bud Structure and Shoot Architecture of Canopy and Understorey Evergreen Broad-leaved Trees at their Northern Limit in East Asia

The morphology of winter buds, shoot growth and branching architecturewas studied in evergreen broad-leaved trees of subtropical/warm-temperaterain forests of southern and central Japan. Winter buds werecategorized into three types based on external morphology anddevelopmental processes: naked, hypsophyllary and scaled buds.Each shoot tip with intermittent growth was covered with a smallnumber of immature leaves or hypsophylls when growth ceased.Hypsophylls protect the apical meristem during its resting period,hence we termed them hypsophyllary buds. In trees with nakedbuds, immature leaves resumed their growth and developed tomature leaves the following spring; thus these trees had nospecial organs to cover shoot tips during winter. In trees withhypsophyllary buds, some hypsophylls covering the shoot tipsthrough the year were shed without further growth when new shootsstarted to grow in the spring. In trees with scaled buds, newlygrowing shoots had hypsophyllary buds at their tips in spring.After the completion of stem elongation, the buds were replacedby scaled buds (often covered with more than 30 scales) in summer.These scaled buds grew during autumn and winter until a newflush of growth the following spring. The three bud types correspondedto forest stratification in the northern-limit forest: the nakedbuds of Rubiaceae and Myrsinaceae in the ground layer; the hypsophyllarybuds of various families (e.g. Symplocaceae, Myrsinaceae) inthe understorey; and the scaled buds of Fagaceae and Lauraceaein the forest canopy. The position and activity of buds on abranch were reflected in the architectural patterns of the treesin different layers of the forest. The scaled-bud trees hadwell-protected, abundant axillary buds and are probably suitedto survive in the forest canopy (with frequent disturbances),whereas the single terminal bud of hypsophyllary-bud trees cansurvive in the less disturbed, resource-limited understoreyof the forest.Copyright 1998 Annals of Botany Company Bud structural type; bud formation; bud growth; shoot elongation; shoot-growth cycle; branching architecture; forest stratification.     

Pyrimidine Nucleotide Biosynthesis in Vinca rosea Cells: Changes in the Activity of the de novo and Salvage Pathways during Growth in a Suspension Culture

Marked changes in the activity of the ‘de novo’and ‘salvage’ pathways of pyrimidine biosynthesisduring growth of Vinca rosea cells in a batch suspension culturewere observed. The activity of these pathways was investigated by determiningthe contribution of ¹⁴C of [2-¹⁴Cluracil, 12-¹⁴Cluridine. and[6-¹⁴Clorotate to the cell constituents and by measuring theactivity of the several enzymes of these pathways. During the lag phase of the culture, ‘uracil-’ and‘uridine-salvage’ pathways made the predominantcontribution to nucleotide biosynthesis, but, following theinitiation of cell division, the ‘de novo’ pathwayfor nucleotide biosynthesis operated appreciably. These results suggest that nucleotide synthesis during cellgrowth in a suspension culture can be divided into two stages:a ‘turnover stage’, during the lag phase of cellgrowth, and a ‘true biosynthetic stage’, which isinitiated in the cell division phase.     

Possible Generational Effects of Habitat Degradation on Alligator Reproduction

ABSTRACT Population decline of the American alligator (Alligator mississippiensis) was observed in Lake Apopka in central Florida, USA, in the early 1980s. This decline was thought to result from adult mortality and nest failure caused by anthropogenic increases in sediment loads, nutrients, and contaminants. Reproductive impairment also was reported. Extensive restoration of marshes associated with Lake Apopka has been conducted, as well as some limited restoration measures on the lake. Monitoring by the Florida Fish and Wildlife Conservation Commission (FFWCC) has indicated that the adult alligator population began increasing in the early 1990s. We expected that the previously reported high proportion of complete nest failure (θ₀) during the 1980s may have decreased. We collected clutches from alligator nests in Lake Apopka from 1983 to 2003 and from 5 reference areas from 1988 to 1991, and we artificially incubated them. We used a Bayesian framework with Gibbs sampler of Markov chain Monte Carlo simulation to analyze θ₀. Estimated θ₀ was consistently higher in Lake Apopka compared with reference areas, and the difference in θ₀ ranged from 0.19 to 0.56. We conducted change point analysis to identify and test the significance of the change point in θ₀ in Lake Apopka between 1983 and 2003, indicating the point of reproductive recovery. The estimated Bayes factor strongly supported the single change point hypothesis against the no change point hypothesis. The major downward shift in θ₀ probably occurred in the mid-1990s, approximately a generation after the major population decline in the 1980s. Furthermore, estimated θ₀ values after the change point (0.21) were comparable with those of reference areas (0.07–0.31). These results combined with the monitoring by FFWCC seem to suggest that anthropogenic habitat degradation caused reproductive impairment of adult females and decreases in θ₀ occurred with the sexual maturity of a new generation of breeding females. Long-term monitoring is essential to understand population changes due to habitat restoration. Such information can be used as an input in planning and evaluating restoration activities.     

NUTRITIONAL CONTROL OF CELL PIGMENTATION IN CHLORELLA PROTOTHECOIDES WITH SPECIAL REFERENCE TO THE DEGENERATION OF CHLOROPLAST INDUCED BY GLUCOSE

1. Measuring the chlorophyll contents and growth of the algalcells grown in media containing different amounts of glucose(G) and urea fas a nitrogen source, N), it was found that theratio N/G determines pigmentation of the cells (colourless,yellow, yellowish green and green) under the experimental conditionsused, and thus a sort of colour map of the differently pigmentedcells was obtained. 2. The bleached cells produced at lower N/G ratios and the greencells obtained at higher ratios could he cultured successivelyunder heterotrophic and photoautotrophic conditions, respectively,and both forms were interconvertible on transferring each celltype into a new medium having appropriate N/G ratio. 3. Studies on these bleaching and greening processes under differentexperimental conditions revealed that the greening requiresessentially the supply of N-sources—no strict specificitywas observed with different N-sources tested—as well aslight, but can take place independently of growth, while thebleaching is caused most strongly by glucose (and fructose)among the carbon sources examined and proceeds essentially independentof light. 4. The bleaching effect of glucose at its higher concentrationsis primarily due to its degradation effect on chloroplast structuresincluding lamellae. This effect of glucose is markedly diminishedat its decreasing concentrations and is also counteracted bythe supply of N-source (urea) of higher concentrations. ¹ This work was partly reported at the Symposium on Cell Differentiationsponsored by the Society of Agricultural Chemistry, Japan, inApril, 1963 and at the Symposium on Nitrogen and Plant by theJapanese Society of Plant Physiologists in October, 1963.     

The rapid spread of invasive Eurasian Collared Doves Streptopelia decaocto in the continental USA follows human‐altered habitats

Understanding factors related to the range expansion trajectory of a successful invasive species may provide insights into environmental variables that favour additional expansion or guide monitoring and survey efforts for this and other invasive species. We examined the relationship of presence and abundance of Eurasian Collared Doves Streptopelia decaocto to environmental factors using recent data from the North American Breeding Bird Survey to understand factors influencing its expansion into the continental USA. A zero‐inflated Poisson (ZIP) model was used to account for excess zero observations because this species was not observed on the majority of survey routes, despite its large geographical range. Model fit was improved when we included environmental covariates as compared with the null model, which only included distance from the route where this species was first observed. Probability of zero count was positively related to the distance from the first route and road density and was inversely related to minimum temperature and distance to coast. Abundance of the species was positively related to road density and was inversely related to annual precipitation and distance to coast. Random intercept by land‐cover type also improved model fit. Model fit was improved with the ZIP model over the standard Poisson model, suggesting that presence and abundance of this species are characterized by different environmental factors. However, overall low accuracy of model‐predicted presence/absence and abundance with the independent validation dataset may indicate either that there are other explanatory factors or that there is great uncertainty in the species’ colonization process. Our large‐scale study provides additional evidence that the range expansion of this species tends to follow human‐altered landscapes such as road and agricultural areas as well as responding to general geographical features such as coastlines or thermal clines. Such patterns may hold true for other invasive species and may provide guidelines for monitoring and assessment activities in other invasive taxa.     

DEVELOPMENT OF PHOTOSYNTHETIC ACTIVITIES DURING THE PROCESS OF CHLOROPLAST FORMATION IN CHLORELLA PROTOTHECOIDES

1. By growing Chlorella protothecoides in a medium rich in glucoseand poor in nitrogen source (urea), entirely chlorophyll-lesscells, called "glucose-bleached’ cells, were obtained.These cells were found to have neither discernible plastid structuresnor photosynthetic activities. When these cells were incubatedin a nitrogenenriched mineral medium without added glucose,a remarkable formation of fully organized chloroplasts occurredin the light and only partially organized chloroplasts weredeveloped in darkness.
2. In the dark-incubated algal cells asmall but appreciable amountof chlorophyll was formed, beingaccompanied by developmentof significant activities for thePMS- and FMN-catalyzed photophosphorylationsand the HILL reaction.The development of the capacity for performingphotosyntheticCO₂-fixation, however, was negligible.
3. During the processof "re-generation" of chloroplasts in thelight, there occurredactive formation of chlorophyll followedby development of allthe photic activities mentioned above.Chlorophyll formationas well as development of the photic activitiesproceeded firstin a manner of autocatalytic reaction and laterin the formof the first-order reaction. It was inferred thatthe light-absorbingagent which mediates the chlorophyll synthesisis chlorophyllitself.
4. The activities for the PMS- and FMN-photophosphorylations,theHILL reaction and photosynthetic CO₂-fixation were recognizedalready in the algal cells at an early stage of greening inthe light, in which the "discs" were developed but no completelamellar structure was observed. Further processes of increaseof these photosynthetic and related activities—as measuredat a high and a lower light intensities—were studied inrelation to the chlorophyll formation under continuous illuminationand under light-dark conditions. It was found that the PMS-photophosphorylationactivity was developed always in parallel with the chlorophyllformation under these different light conditions. Developmentof the activities for the other photic reactions, however, lagged,to different extents, behind the formation of chlorophyll inthe later phase of greening of algal cells under these conditions.
5. Based on these results the modes of formation of the componentsinvolved in these photic reactions were surmised.

(Received September 15, 1965; )     

LOCALIZATION OF DYNEIN IN SEA URCHIN EGGS DURING CLEAVAGE*

Detection and localization of dynein in cleaving sea urchin eggs were attempted using antidynein serum (prepared against a tryptic fragment of dynein, Fragment A, of sea urchin sperm flagella) and fluorescein conjugated goat antiserum to rabbit γ-globulin. In both unfertilized and newly fertilized eggs, fluorescence was distributed rather uniformly within the cells but was absent from the nuclei. At prophase, intense fluorescence was observed on both sides of nucleus, suggesting accumulation of dynein in developing asters. From metaphase to anaphase, the whole mitotic apparatus (MA) was stained with the exceptions of the chromosomes and pole areas. Fluorescence then again became dispersed within the eggs. Throughout the mitotic process and cytokinesis, the egg cortex including the cleavage furrow was stained intensely, presumably reflecting the presence of dynein in this region. Similar distributions of fluorescence were obtained with the isolated MAs. Neither non-immune serum nor the antiserum to which Fragment A was absorbed stained the eggs. Little staining was obtained with the antiserum against starfish egg myosin. The results, together with the finding that the chromosome motion in the isolated MAs was completely inhibited by anti-dynein serum, but not with the anti-myosin serum, suggest an active role played by a tubulin-dynein system in mitosis.