Hydroxyl- and Bicarbonate-Associated Transport Processes in Chara corallina: Studies on the Light-Dark Regulation Mechanism

Lucas, W. J. and Ogata, K. 1985. Hydroxyl– and bicarbonate–associatedtransport processes in Chara corallintr. Studies on the light–darkregulation mechanism.—J. exp. Bot. 36: 1947–1958.Experiments were undertaken on the fresh water alga Chara corallinato investigate the nature of the coupling between the chloroplastsand the light–dependent OH^– and -associated plasmalemma transport systems. Electrophysiologicalexperiments, in which DCMU was employed, revealed that thischemical could elicit a hyperpolarization of the membrane potentialthat was identical to that normally obtained by turning offthe light. This DCMU–induced hyperpolarization was obtainedunder control () and phosphate–decoupled conditions (). Measurements of the extracellular electric potentialswhich are associated with the acidic () and alkaline (OH^–) regions, indicated that, in the presenceof control ()or phosphate–decoupled conditions, normal profiles were established under air, oxygenor nitrogen environments. These results indicate that the generationof the control signal(s) is related to events associated withchloroplast electron transport, rather than to changes in theflow or levels of carbon intermediates within the reductivepentose phosphate or photorespiratory cycles. Although the levelof oxygen was found to have no effect on the light–inducedactivation of the OH regions, we found that in pure oxygen thedark–induced inactivation of the OH^– efflux systemwas delayed, and that partial transport function could be maintainedin the dark. The possible involvement of changes in either theratio of oxidized to reduced ferridoxin or NADP^? to NADPH, aspart of this light–mediated control signal, is discussed. Key words: Chara corallina, Plasma membrance transport, OH^– and , regulation     

Reactivity of a Monoclonal Antibody Raised against Human Leukemic Cells to Embryonic and Adult Tissues of the Mouse and Teratocarcinomas

C-9-1, a monoclonal IgM antibody raised against human null cell acute lymphocytic leukemia cells reacted with restricted regions of embryonic and adult tissues of the mouse. The antigen positive sites in the embryos included embryonic ectoderm, visceral endoderm, trophoblastic cells invading the maternal decidua of 5∼7-day embryos, primordial germ cells of 10∼12-day embryos, epithelium of nasal chamber, the bronchus, Mullerian duct, epididymis and bladder of 12∼17-day embryos. In the adult mice, C-9-1 antigen was detected in renal tubules, a part of stomach, bladder, endometrium and epididymal sperm. Embryonal carcinoma cells, but not endodermal cells of teratocarcinoma expressed the antigen. Thus, C-9-1 antigen showed distribution similar to SSEA-1. However, C-9-1 antigen was not detected in preimplantation embryos, nor in oviduct, both of which are positive for SSEA-1.     

Pigments and a UV-absorbing substance in corals and a blue-green alga living in the Great Barrier Reef

Pigments and UV-absorbing substances in several species of coralsand a blue-green alga harvested in the environs of the GreatBarrier Reef were studied by measuring the in vivo reflectionspectra of intact samples and absorption spectra of their waterextracts with a recording spectrophotometer set on a biologicalresearch vessel. Red, pink, mauve and violet colors of fourspecies of Acropora were thus found to be due to differencesin the relative content of two pigments designated as P(pigment)-560and P-590, according to the maximum wavelength in mµ oftheir major absorption peaks. A yellow species of Acropora anda red species of Pocillopora contained different pigments, P-500and P-480, respectively. All these five species of corals contained,in addition to the above pigments, a UV-absorbing substancehaving an absorption peak near 320 mµ. The contents ofthis substance in the organisms seemed to be very high as judgedfrom its band height relative to band heights of the visiblepigment bands. Blue-green algal cells harvested near the sameenvirons contained a similar UV-absorbing substance in additionto phycobilin pigments. The spectral characteristics of thepigments and the UV-absorbing substance found in the coralsand alga are presented in this paper. ¹The present study was carried out in cooperation with Drs.F. T. HAXO, P. HALLDAL and S. W. JEFFREY on the research vessel,R. V. "Alpha Helix", of University of California during the1966 expedition to the Great Barrier Reef, North Queensland,Australia, and was supported by the National Science Foundationof the U. S. A. (Received December 3, 1968; )     

Cell Membrane Stability and Leaf Surface Wax Content as Affected by Increasing Water Deficits in Maize

A field experiment was conducted with a water-stressed treatmentand well-watered control using eight maize (Zea mays L.) cultivars.Effects of water deficits on cell membrane stability (CMS) measuredby the polyethylene glycol (PEG) test, leaf surface wax content,and relative growth rate were investigated. Cytoplasmic lipidcontent was also analysed. Cell membrane stability and leaf surface wax content increasedwith the degrees of stress. Tolerance to drought evaluated asincrease in CMS under water deficit conditions was well differentiatedbetween cultivars and was well correlated with a reduction inrelative growth rate under stress. A negative correlation wasfound between percentage injury in the PEG test and leaf surfacewax content. High phospholipid contents were observed in tissuesof drought tolerant cultivars under water deficit conditions. Key words: Cell membrane stability, cytoplasmic lipid, drought tolerance, leaf surface wax, relative growth rate     

Cell Membrane Stability and Leaf Water Relations as Affected by Potassium Nutrition of Water-Stressed Maize

A field experiment was conducted to investigate the effect ofK nutrition under water stress conditions on cell membrane stabilitymeasured by the polyethylene glycol test, plant growth, internalplant water relations and solute and mineral concentrationsin maize (Zea mays L.). Water-stressed plants showed greateradaptation to water deficits at higher K levels. Cell membranestability increased, leaf water potential and osmotic potentialdecreased, turgor potential increased and stomatal resistancedecreased with increasing K nutrition. Osmotic adjustment wasevident and it may have been influenced by increased K⁺ concentrationsin leaf tissues with increasing K nutrition. Higher leaf thicknessand higher leaf water content were observed at higher K levels.Results suggested that higher supplies of K nutrition may increaseplant production during periods of water stress. Key words: Zea mays L., cell membrane stability, leaf water potential, osmotic adjustment, osmotic potential, potassium nutrition, water stress     

Salinity and the Hydraulic Conductance of Roots

The effect of salinity on hydraulic conductance of intact roots of tomato (Lycopersicon esculentum Mill.) and sunflower (Helianthus annuus L.) was determined in split-root experiments using salinized nutrient solutions. Experiments were conducted in controlled climate chambers under two or three relative humidity levels and four solution osmotic potential levels. The relationship between water flux through roots (J_v) and total water potential difference between the leaves and the root medium (Δψ) was linear, usually with a small intercept. Thus, the root hydraulic conductance (L) was not affected by salinity within the range of fluxes obtained in these experiments, with L= 0.036 mm h^?1 bar^?1 for tomato and L= 0.0167 mm h^?1 bar^?1 for sunflower. Our results agreed with theoretical analysis of coupled water and ion uptake. From Cl^? and Na⁺ uptake data, the reflection coefficient (o) for tomato roots was calculated as 0.956, which was compatible with the near-zero intercept. A large intercept for sunflower could not be readily explained. Relative humidity strongly affected root growth, with more rapid growth under low humidity conditions. Transpiration of sunflower plants was reduced by 20% when the relative humidity was increased from 34% to 84%, whereas transpiration in tomato was reduced 50%.