PHYTOCHROME CONTROLLED NYCTINASTY IN ALBIZZIA JULIBRISSIN. I. ANATOMY AND FINE STRUCTURE OF THE PULVINULE

Under appropriate experimental conditions, phytochrome controls leaflet closure in Albizzia by regulating differential turgor changes in motor cells of the pulvinule. Closure occurs when subepidermal dorsal cells expand and ventral cells become compressed; reopening involves the reverse changes. The internal cells surrounding the vascular core remain relatively unchanged during leaflet movement. Fine structural studies revealed several unusual features of the motor cells including: (1) fibrils oriented parallel to one another in the cytoplasmic matrix; (2) numerous spherosomes that appear to coalesce and enlarge to form vacuoles; and (3) a multivacuolate condition.     

CYTOLOGICAL BASIS FOR CYTOPLASMIC INHERITANCE IN PSEUDOTSUGA MENZIESII. II. FERTILIZATION AND PROEMBRYO DEVELOPMENT

Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) ovules were used to study male gamete formation, insemination of the egg, and free nuclear and cellular proembryo development. Two male nuclei form as the pollen tube either reaches the megaspore wall or as it enters the archegonial chamber. No cell wall separates them. They are contained within the body-cell cytoplasm. A narrow extension of the pollen tube separates the neck cells and penetrates the ventral canal cell. The pollen tube then releases its contents into the egg cytoplasm. The two male gametes and a cluster of paternal organelles (plastids and mitochondria) migrate within the remains of the body-cell cytoplasm toward the egg nucleus. Microtubules are associated with this complex. The leading male gamete fuses with the egg nucleus. The zygote nucleus undergoes free nuclear division, but the cluster of paternal organelles remains discrete. Free nuclei, paternal and maternal nucleoplasm, maternal perinuclear cytoplasm, and the cluster of paternal organelles migrate en masse to the chalazal end of the archegonium. There, paternal and maternal organelles intermingle to form the neocytoplasm, the nuclei divide, and a 12-cell proembryo is formed. The importance of male nuclei or cells, the perinuclear zone, and large inclusions in cytoplasmic inheritance are discussed in the Pinaceae and in other conifer families. This completes a two-part study to determine the fate of paternal and maternal plastids and mitochondria during gamete formation, fertilization, and proembryo development in Douglas fir.     

THE COLOR VISION OF DICHROMATS : II. SATURATION AS THE BASIS FOR WAVELENGTH DISCRIMINATION AND COLOR MIXTURE

1. Wavelength discrimination for the colorblind is entirely determined by saturation differences in the spectrum. From the neutral point to the short-wave end, his spectrum may be completely matched by 440 mµ plus white; to the long-wave end by 650 plus white. The proportion of color to white, hence the relative saturation, changes rapidly in the region of small Δλ at the center, and slowly in regions of large Δλ at the ends. 2. The data of spectrum gauging with two primaries (color mixture) by the dichromat are shown to contain the saturation distribution in the spectrum for the dichromat. This is because each mixture of primaries may be considered as composed of a mixture which matches white and of an excess of one primary. The data when so computed yield saturation distributions almost identical with those found by direct measurement, and show that on each side of the neutral point the basis of color mixture for the colorblind lies in saturation and not in hue differences. 3. To judge by these measurements, the spectrum for the protanope and deuteranope is composed of only two hues, themselves probably of low saturation, situated one at each end. Toward the center these hues decrease still more in saturation until they completely disappear in the white of the neutral point.     

PECTIN-PROTEIN INTERACTION AS A BASIS FOR AUXIN-INDUCED ALTERATION OF PROTEIN HEAT COAGULABILITY

Galston , Arthur W., Ravindar Kaur , Nirmala Maheshwari , and Satish C. Maheshwari . (Yale U., New Haven, Conn.) Pectin-protein interaction as a basis for au xin-induced alteration of protein heat coagulability. Amer. Jour. Bot. 50(5): 487–494. Illus. 1963.—The in vivo administration of 2,4-D or other auxins to etiolated or green pea stem sections results in a decreased heat coagulability of the macromolecular components of the particle-free cytoplasm of these tissues. Addition of auxin to homogenates is without effect. Gibberellins alone are also without effect, but may enhance the in vivo action of auxin. The altered heat coagulability may become apparent as soon as 4–6 hr after auxin administration, though longer induction periods are sometimes necessary. The auxin eff'ect is prevented by general metabolic inhibitors and most effectively by ethionine, whose inhibitory action is completely reversed by methionine. Electrophoresis on paper and on starch revealed no major differences between the proteins of control and auxin-treated stems. Approximately 90% of the weight of the heat coagulum can be accounted for as protein; small quantities of nucleic acids, lipids, polysaccharides and pectins are also present. The “soluble pectin” content of the homogenate before heat coagulation is at least doubled by auxin treatment. This increase is also inhibited by ethionine, whoso effect is annulled by methionine. Addition of citrus pectin to control homogenates stabilizes the proteins against heat coagulation. It thus appears likely that the effect of auxin on the heat coagulability of the cytoplasmic proteins can be explained through effects on the metabolism of the materials which have been called “cold-water-soluble pectins.”     

THE PHYSIOLOGICAL BASIS OF MORPHOLOGICAL POLARITY IN REGENERATION. II

1. The experiments show that the mass of air roots formed in a stem increases with the mass of the leaf attached to the stem, though it has not been possible to establish an exact mathematical relation between the two masses, owing to unavoidable sources of error. 2. Darkened leaves do not increase the mass of roots formed. 3. In stems suspended horizontally air roots appear on the lower side of the stem, with the exception of the cut end where they usually appear around the whole circumference of the stem. When the lower half of a stem suspended horizontally is cut off, roots are formed on the upper side. It is shown by experiments on leaves suspended horizontally that the more rapidly growing roots and shoots on the lower side inhibit the root and shoot formation in the upper half of such a leaf; and likewise the more rapid formation of roots on the lower side of a horizontally suspended stem seems to account for the inhibition of root formation on the upper side of such a stem. Likewise the more rapid growth of shoots on the upper side of a stem suspended horizontally is likely to inhibit the growth of shoots on the lower side. 4. Each leaf contains in its axil a preformed bud capable of giving rise to a root, which never grows out in the normal stem on account of the inhibitory influence of the normal roots at the base of the plant. These dormant root buds are situated above (apically from) the dormant shoot bud. The apical root buds can be caused to develop into air roots when a piece of stem is cut out from a plant from which the leaves except those in the basal node of the piece are removed. The larger these basal leaves the better the experiments succeed. 5. These apical air roots grow out in a few days, while the roots at the basal end of the stem (which in our experiments dip into water) grow out about a week later. As soon as the basal roots grow out in water they cause the air roots in the more apical region of the stem to dry out and to disappear. 6. In addition to the basal roots, basal nodes have also an inhibitory effect on the growth of the dormant root buds in the apical region of a stem. This is indicated by the fact that a stem with one pair of leaves near the base will form apical air roots more readily when no node is situated on the stem basally from the leaf than if there is a node basally from the leaf.     

NUTRIENT UPTAKE KINETICS IN PHYTOPLANKTON: A BASIS FOR NICHE SEPARATION1

Daily patterns of incorporation of carbon dioxide and inorganic phosphate were measured in phytoplankton from Lake George, New York, in January and February 1972. Rates of photosynthesis oscillated in phase for the entire assemblage and for individual cells of the diatoms Asterionella, Tabellaria, and Fragilaria. The photosynthetic capacity was maximal in the early afternoon. Daily patterns of phosphate uptake were also rhythmic. At ambient concentrations the assemblage takes up phosphate maximally in the morning while individual cells of the large diatom take it up maximally in the evening. A kinetic analysis of phosphate uptake indicated 2 velocities of uptake for cells of Tabellaria and Fragilaria: a hyperbolic function at small and an apparently linear relationship at relatively large concentrations. The large diatoms, in contrast to the total assemblage, functioned maximally at 2 separate times of the day: in the evening at ambient levels and in the morning at 0.4 μM and larger concentrations. Temporal stratification of the nutrient niche may be achieved by several uptake mechanisms in the algal cell that function at different times of the day or with a variable uptake velocity.     

A CONTROLLED TECHNIQUE FOR VEIN STRIPPING

A number of difficulties encountered in vein stripping operations for varicose veins in the legs have been overcome by use of a technique evolved by adaptation and modifications of various reported methods.The stripping instrument is passed from below upward, the valves or branches offering less impediment to its passage in that direction.Inserting the tip of the instrument at the ankle through an incision in the vein while it is still in continuity is easier than introducing it into the end of a transected vein. Ligation of major superficial branches or subfascial division of communicating veins can be readily carried out while the stripper is still in place in the vein.Applying pressure bandages to the entire length of the leg before removing the stripper and the telescoped vein diminishes the chances of ecchymosis yet does not hinder withdrawal of the instrument and the vein.