Development of tannin vacuoles in chalaza and seed coat of barley in relation to early chalazal necrosis in the seg1 mutant

Structural development of grain tissues of maternal origin in normal and seg1 barley (Hordeum vulgare L. cv. Betzes) was examined using light and electron microscopy. Chalaza and seedcoat cells of normal grains developed prominent tannin vacuoles which persisted throughout the grain-filling period. Tannins were present in the same tissues of seg1, but no large central vacuoles developed. Instead, the chalaza and nucellar projection degenerated and were crushed, presumably terminating sugar flow and causing formation of shrunken grains (35–55% normal dry weight). Tannins were localized using various histochemical stains. Extracts of chalaza and adjacent tissues contained proanthocyanidins which yielded delphinidin and cyanidin upon hydrolysis in boiling HCl. We suggest that the basis of the seg1 phenotype may be abnormal compartmentation of tannins causing precipitation of cytoplasmic proteins and early death of chalazal cells.Abbreviations FAA Formalin-acetic acid-ethanol - PAS periodic acid Schiffs reagent     

Interactions of galactose-binding lectins with plant protoplasts

Summary Protoplasts isolated from cell suspension cultures of carrot (Daucus carota L.) and leaves of tobacco (Nicotiana tabacum L.) were treated with three lectins specific for galactosyl residues. After incubation with RCA I (Ricinus communis agglutinin, molecular weight 120,000) conjugated to ferritin or fluorescein, freshly isolated protoplasts displayed heavy labeling of their surfaces. Moreover, they agglutinated rapidly when exposed to low concentrations of RCA I. In parallel studies, PNA (peanut agglutinin) also bound extensively to the protoplast plasma membranes whileBandeiraea simplicifolia lectin I attached relatively weakly. When protoplasts were cultured for two days and then incubated with conjugates of RCA I and PNA, additional binding sites were revealed on the regenerating walls.The results indicate that galactosyl residues are distributed densely over the surface of plant protoplasts. They also allow inferences to be made regarding the positions and linkages of the galactose groups being recognized by the lectins. Moreover, they open up the question whether the galactosyl moieties detected in the wall derive from those labeled on the plasma membrane. To conclude, we make comparisons with binding by concanavalin A, and predict that galactose-recognizing lectins will join and in certain respects prove superior to concanavalin A as probes of the plant cell surface.     

SUBCELLULAR DISTRIBUTION OF A HEAT-STABLE PROTEIN INHIBITOR OF CYCLIC AMP-DEPENDENT PROTEIN KINASE IN RAT BRAIN

Abstract— Cyclic AMP (cAMP)-dependent protein kinase catalyzes the phosphorylation of polypeptidic serine and threonine residues according to the following chemical equation: ATP + protein → phospho-protein + ADP. A heat stable, trypsin labile factor present in brain, skeletal muscle and other tissues inhibits enzymatic phosphorylation of some proteins and enhances that of others. Since brain is one of the richest sources of adenylate cyclase, cAMP, cAMP-dependent protein kinase and the heat stable protein kinase inhibitor and because they may play a role in neurotransmission, an investigation of the subcellular distribution of the heat stable factor in rat brain was undertaken. Although present in the nuclear, mitochondrial and microsomal fractions, the highest activity of protein kinase inhibitor is in the soluble fraction: its activity parallels that of the cytoplasmic enzyme marker, lactate dehydro-genase. The inhibitory activity is also found in the synaptosome or pinched-off nerve ending fraction. Following osmotic lysis of this fraction, about 90% of the factor occurs in the soluble fraction. On the other hand, only 40% of the cAMP-dependent protein kinase is solubilized and 60% remains membrane-bound. Using this membrane-bound protein kinase, phosphorylation of endogenous substrate is unaltered by inhibitor, but phosphorylation of added histone substrate is decreased.     

OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XXVII. A FURTHER STUDY OF PHYSODERMA HYDROCOTYLIDIS VIÉGAS AND TEIXEIRA

A further study of Physoderma hydrocotylidis from California on its host Hydrocotyle ranunculoides gives further details on its structure and development. EM micrographs reveal that the notably thin wall of the resting spore consists of an outer, an intermediate, and an inner layer. The complete wall thickness from measurements of these EM preparations is only 0.5 μm, the thinnest of any known Physoderma resting spore. Such resting spores germinate readily in 2–5 h by the dehiscence of a broad cap and formation of a protruding endosporganium. Zoospores from the latter infect epidermal host cells and produce either the endobiotic, polycentric rhizoidal system with tenuous filaments, turbinate cells and eventually resting spores, or a hitherto unknown epibiotic, monocentric, rhizidiaceous sporangial stage. Zoospores from the latter may all bear colorless lipid globules or all faintly orange-colored ones.     

Peptide transport in intestinal and renal brush border membrane vesicles

A longstanding question about the possible dependence of transmembrane peptide transport on sodium has now been resolved. Recent studies with purified intestinal brush border membrane vesicles have shown that peptide transport across this membrane is Na⁺-independent and occurs by a non-concentrative mechanism. Similar studies with renal brush border membrane vesicles have established for the first time the presence of a peptide transport system in mammalian kidney. The essential characteristics of peptide transport in these two tissues are the same. However, it still remains to be seen whether a new mechanism other than the Na⁺-gradient, hitherto unrecognized, is involved in energizing the active transport of peptides in vivo in mammalian intestine and kidney.     

The effect of vapor pressure on stomatal control of gas exchange in Douglas fir (Pseudotsuga menziesii) saplings

Summary Increasing leaf to air vapor pressure deficit (VPD) caused reductions in stomatal conductance of both current year and previous season needles of Pseudotsuga menziesii saplings. The stomata of current year needles were found to be more responsive to changes in VPD than those of previous season needles. The reductions in stomatal conductance of current year needles were not associated with decreases in xylem pressure potential. In fact, the reductions in stomatal conductance of current year needles were sometimes sufficient to reduce transpiration and thus raise xylem pressure potential even though VPD was increasing. There was a decline in stomatal responsiveness to VPD in current year needles between early and late summer. Pressure-volume curves determined for different age needles at different times of the year suggested that differences and changes in stomatal responsiveness to VPD may have been caused in part by differences and changes in needle water potential components. Hexane washes of current year needles during the late summer succeeded in partially restoring their VPD sensitivity, suggesting that changes in the water permeability of the external cuticle during needle maturation may also have played a role in causing the summer decline in VPD responsiveness.In both current and previous year needles VPD-induced changes in stomatal conductance had a greater relative effect on transpiration (q _w) than on net photosynthesis (Ph_N). In maturing needles the ratio of the sensitivities of transpiration and net photosynthesis to changes in stomatal conductance, (q _w/g _s)/Ph_N/g _s), remained nearly constant as VPD was varied. This provides experimental support for a recent hypothesis that stomata respond to environmental fluctuations in such a manner as to maintain the above ratio constant, which optimizes CO₂ uptake with respect to water loss.     

The effect of light on stomatal control of gas exchange in Douglas fir (Pseudotsuga menziesii) saplings

Summary Attached twigs of young Pseudotsuga menziesii (Mirb.) Franco plants were subjected to variations in irradaince. Stomatal responsiveness to irradiance, measured in an open type gas exchange system, varied seasonally. During the autumn and winter, stomatal conductance was relatively unresponsive to changes in irradiance, but during the summer stomatal conductance decreased in response to reduced irradiance. The summer stomatal response to irradiance was such that a nearly constant ratio of stomatal conductance to net photosynthesis was maintained as irradiance was varied. This caused intercellular CO₂ concentration (c _i) and water use efficiency (net CO₂ uptake/transpiration) to also remain relatively constant. At constant irradiance, stomatal conductance was relatively insensitive to experimentally-induced changes in c _i. This, and the observation that c _i remained relatively constant as irradiance was varied, suggest that changes in c _i played a minor role in mediating the stomatal response to light.The ecological significance of the seasonal changes in stomatal response to light is discussed.     

2-β-d-Glucopyranosyloxy-2-methylpropanol in Acacia sieberana var. woodii

A new diol glucoside, 2-β-d-glucopyranosyloxy-2-methylpropanol, the first reported naturally occurring monoglucoside of an aliphatic dihydric alcohol, was isolated from pods of Acacia sieberana var. woodii. Structure elucidation was based on ¹ H and ¹³C NMR spectroscopy, and enzymatic analyses. The compound was hydrolysed very slowly by almond β-glucosidase, but cleaved by a β-glucuronidase enzyme complex from Helix pomatia.