The Effects of Conditions of Growth, Extraction and Reaction on a Nucleotide Phosphatase Activity Obtained from the Shoot-Root Axes of Pisum sativum var. Alaska Seedlings

Nucleotide phosphatase activity in extracts from etiolated peaseedlings (Pisum sativum var, Alaska) was studied. A markedincrease followed rupture of the seed coat by the elongatingradicle, indicating a dependence on aerobic respiration fordevelopment of the activity. Activity from the shoot-root axiswas directly correlated with axis size, inhibition of growthresulting in a reduced activity. Growth in continuous illuminationalso reduced activity, as did imbibition of phenylalanine, tyrosine,glutathione, and sodium phosphate. The activity was greaterin the shaft regions of the axis than in the tip regions. About30 percent of the activity was associated with the nuclear—mitochondral—cellwall pellet, while the reminder was more or less evenly distributedbetween a membranee fraction of high specific activity and asoluble fraction. The effects of substractes, ions, and inhibitorson the activities of membrane and soluble fractions was quitedifferent.     

Electrochemical State of Potassium and Sodium in Free Cells of Acer pseudoplatanus

The intracellular distribution of K⁺ and Na⁺ ions has been determined by compartmental analysis of isotope exchange. The simultaneous measurement of electrical potentials allowed us to show that the distribution of K⁺ was close to thermodynamic equilibrium while the internal concentration of Na⁺ was well below the value predicted for the equilibrium. The efflux of Na⁺ was more sensitive to temperature than its influx. Both ouabain and variations in the external levels of KCl produced weak and inconsistent effects, observations which would emphasize the difference between the Na⁺ extrusion mechanism of plants and animals. The Na⁺ extrusion system of Acer cells ceased to be functional in Na⁺-depleted cells but recovered its function if the cells were placed in 10 mM NaCl, which suggests that the extrusion system was induced by the level of internal Na⁺ ions.     

DURATION OF EGG-CHAMBER GROWTH IN YOUNG IMAGINES OF DROSOPHILA MELANOGASTER MEIG

After [³H] thymidine injection to new-hatching Drosophila melanogaster females the migration of labelled egg-chambers through the ovarioles was studied by autoradiographies of the ovaries at daily intervals. The growth duration of egg-chambers which progressed during the first 48 hr was 24 hr longer than the growth duration of chambers progressing thereafter. This temporary delay of ovarian activity was related to endocrine modifications occuring in female during this s period and particularly to a JH-ecdysone interaction.     

Dependence of the Stomatal Index on Environmental Factors during Stomatal Differentiation in Leaves of Vigna sinensis L.: 1. EFFECT OF LIGHT INTENSITY

The stomatal index of the trifoliate leaves of the Cowpea isa function not only of the total radiation received but alsoof variations in radiation during the 6 d preceding the majorphase of the unfolding of the leaf lamina. Hence, for sun plantsa whole day in the shade can cause a decrease in the stomatalindex provided this day occurs during the period defined above.For shade plants it is shown that a single day of high lightintensity during this critical period will cause an increasein the stomatal index. The latter is thus a characteristic foreach individual leaf. It is postulated that the site of photoperceptioncontrolling the stomatal index is located in the expanded adultleaves. Excision and transfer of still unfolding leaves to aculture medium partially prevents the influence of the olderexpanded leaves on the stomatal index of the excised leaf.     

A geometric morphometric assessment of the effects of environment and cladogenesis on the evolution of the turtle shell

In the largest group of extant turtles, the Testudinoidea, the acquisition of an aquatic or terrestrial way of life has occurred within two clades, allowing the study of homoplasy linked to environment (commonly named convergence). Here we appraise the respective importance of two sources of morphological variation: a major cladogenetic event and a major environmental shift (aquatic vs. terrestrial). The repeatability of the same evolutionary process (environmental change) allows an assessment of the weights of both natural selection and phylogenetic constraints on several morphological features of the shell. These sources of morphological variance on the complex shell structure were studied using geometric morphometrics. We depict the morphological variation of three parts of the turtle shell: epidermal carapace, bony carapace, and plastron. In the three structures, we found that both phylogeny and environment were significant sources of morphological variation, and geometric morphometrics allowed the pattern of morphological variation due to each effect to be assessed. The assessment of the homoplasy due to environment and of the pattern of morphological variability suggests that the carapace has undergone similar morphological changes between aquatic and terrestrial environments within the two clades. The radiation of the Testudinoidea is interpreted as an adaptive radiation.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 485–501.     

Comparison of Horizontal Spread of White Clover (Trifolium repensL.) Grown Under Two Artificial Light Sources Differing in their Content of Blue Light

The effects of blue light on the growth and development of differentbranches were studied to determine if variations in the bluelight supply modified the horizontal spread of white clover.Cuttings of white clover (‘Huia’) were grown for56 d in two controlled chambers under conditions similar exceptfor level of blue light (BL). The horizontal spread of whiteclover was characterised by the phyllochron, internode lengthand branching or flowering of different axes. The responsesto a reduction in BL were different according to axis degree:(1) on the main axis, lowering BL slightly decreased the phyllochronand had no effect on internode length or stolon length; (2)on older primary branches, it decreased their phyllochron, butreduced stolon length due to a reduction in internode length;(3) on secondary branches, it increased the phyllochron anddecreased internode length, triggering a strong reduction instolon length (up to 54%). Moreover, an increase in BL reversedthese effects. The switch to lower BL or higher BL had no effecton internode length of primary branches, but triggered changesin internode length of the main axis. These differential effectsof variations in BL on the morphogenesis of different branchesare discussed in relation to the clonal integration of variationsin light composition. Changes in the horizontal spread of whiteclover induced by BL could play a role, combined with responsesto low red:far-red ratio and low photosynthetic photon flux(PPF) in the strategy of horizontal colonisation and shade-avoidanceof white clover.Copyright 1998 Annals of Botany Company Blue light, branching, horizontal spread, morphogenesis, phyllochron, plant development, plant morphology, stolon growth,Trifolium repensL., white clover.     

On the races of Arenaria tetraquetra L. (Caryophyllaceae)

FAVARGER, C. & NIETO FELINER, G., 1988 On the races of Arenoria tetraquetra L. (Caryophyllaceae). The caryological study of some Betic populations of Arenaria tetraquetra northwards from Sierra Nevada has proved that they are polyploids ( 3x, 4x, 5x ). Even though their Rowers are pentamerous, they differ from the Nevadean Arenaria tetraguetra subsp. amabilis (2x ) not only by the chromosome number but also by the micromorphology of the seed coat and the hairiness of the stem internodes. They also differ from Arenaria tetraquetra subsp. tetraquetra , the Rowers of which are tetramerous and the degree of polyploidy higher (6x in the Pyrenees, 7x in the Sierra de Pela eastwards from Sierra de Guadarrama). The authors proposed to give a subspecific status to such Betic polyploid populations with a new combination. They suggest a hypothesis to explain the evolution of the A. tetraguetra polyploid complex.