摘要:

AbstractExtracts prepared from endosperms of germinating seeds of Scots pine,Pinus sylvestrisL., rapidly hydrolysed the β‐naphthylamides of L‐phenylalanine and L‐leucine optimally at pH 6.5 and that of L‐arginine at pH 7.7. Disc electrophoresis followed by activity staining showed that the activities were due to two naphthylamidases (aminopeptidases) with different substrate specificities.Seeds were allowed to germinate at 20°C on agar gel in the dark and the activities on the three substrates were assayed from separated endosperms and seedlings at various stages of germination. The activities in the endosperm of resting seeds were relatively high and they remained unchanged throughout the period of reserve protein mobilization (seedling length up to 50 mm), after which they began to decrease. The activities of the naphthylamidases are rather small compared with those of the two alkaline peptidases of pine, contributing about 17% of the total amino‐peptidase activity in the endosperm of germinating seeds. The total aminopeptidase activity is sufficient to account for the rate of storage protein mobilization during germination.In the seedlings the naphthylamidase activities (per seedling) increased continuously during germination, and activities per g dry weight were higher than those in th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04861.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractApplication of gibberellic acid to the apex of dwarf bean plants (cv. Alabaster) stimulated the elongation growth of epicotyl and hypocotyl but showed no significant effect on elongation growth in a normal cultivar (‘Blue Lake’). Gibberellin‐treatment of dwarf plants was characterized by about twofold increase in the level of endogenous auxin. Maximum increase in IAA level was observed after 48 h of GA treatment. There was less increase in IAA content in normal bean plants. — Gibberellin treatment to excised epicotyl and hypocotyl sections of either dwarf or normal cultivar showed no effect on elongation growth. However, a considerable increase in the auxin level was observed in the sections of the dwarf cultivar. The maximum effect occurred with only 1 h incubation in basal medium containing gibberellin. — The indolo‐α‐pyrone spectro‐fluoremetric method for IAA determ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04862.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractExperiments were conducted to elucidate the basis of the observation that different strains ofRhizobiuminfect particular legumes. Rhizobia specific for a variety of legumes were grown with13PO2−4and exposed to pea roots (Pisum sativumL.),R. leguminosarum128C53, which nodulates pea, did not attach to the roots in greater numbers than those strains of rhizobia incapable of infecting pea roots. A complex ofR. leguminosarum128C53 conjugated to a fluorochrome‐labeled antibody exhibited a striking attachment to the tips of pea root hairs, where infection normally occurs, but this fluorescent complex also bound to the root hairs ofCanavalia en siformisDC.,Lupinus polyphyllusLindl.,Trifolium pratenseL., andMedicago sativaL., which are not infected by this bacterium. A reproducible, quantitative technique developed for studying interactions between fluorochrome‐labeled lectins and rhizobia revealed no relationship between lectin‐Rhizobiuminteractions and the capacity to infect a plant. The data are interpreted as suggesting that simple attachment ofRhizobiumto a legume root is not the basis of host‐symbiont specificity in th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04863.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractUptake and fluxes of sodium, rubidium (instead of potassium), and chloride ions in segments of 3‐week‐old sugar beet roots were studied. Radioactive22Na,86Rb and36Cl were used for labelling of the ions. Compartmental analysis was used to obtain the fluxes and concentrations in the cell compartments. The passive or active character of the movements was examined by the Ussing‐Teorell equation and compared with electropotential measurements.In the case of sodium, net flux was in the outward direction over both tonoplast and plasmalemma, but the active components were directed away from the cytoplasm. Potassium was close to equilibrium. Chloride was actively transported from the medium to the cytoplasm, and — contrary to observations in other systems — from the vacuole to the cytoplasm. This unusual situation may be caused by a loss of sugar, both by lowering the energy supply and by formation of orga

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04864.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractExposure of cucumber seedlings (Cucumis sativusL.) to chilling temperature resulted in injuries such as increased leakage of cellular materials, loss of water and wilting. In addition, the development of the seedlings after the exposure to chilling was impaired. Abscisic acid applied to the seedlings prior to chilling significantly ameliorated these injuries.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04865.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe relationship between leaf resistance to water vapour diffusion and each of the factors leaf water potential, light intensity and leaf temperature was determined for leaves on seedling apple trees (Malus sylvestrisMill. cv. Granny Smith) in the laboratory. Leaf cuticular resistance was also determined and transpiration was measured on attached leaves for a range of conditions.Leaf resistance was shown to be independent of water potential until potential fell below — 19 bars after which leaf resistance increased rapidly. Exposure of leaves to CO2‐free air extended the range for which resistance was independent of water potential to — 30 bars.The light requirement for minimum leaf resistance was 10 to 20 W m−2and at light intensities exceeding these, leaf resistance was unaffected by light intensity.Optimum leaf temperature for minimum diffusion resistance was 23 ± 2°C. The rate of change measured in leaf resistance in leaves given a sudden change in leaf temperature increased as the magnitude of the temperature change increased. For a sudden change of 1°C in leaf temperature, diffusion resistance changed at a rate of 0.01 s cm−1min−1whilst for a 9°C leaf temperature change, diffusion resistance changed at a rate of 0.1 s cm−1min−1.Cuticular resistance of these leaves was 125 s cm−1which is very high compared with resistances for open stomata of 1.5 to 4 s cm−1and 30 to 35 s cm−1for stomata closed in the dark.Transpiration was measured in attached apple leaves enclosed in a leaf chamber and exposed to a range of conditions of leaf temperature and ambient water vapour density. Peak transpiration of approximately 5 × 10−6g cm−2s−1occurred at a vapour density gradient from the leaf to the air of 12 to 14 g m−3after which transpiration declined due presumably to increased stomatal resistance. Leaves in CO2‐free air attained a peak transpiration of 11 × 10−6g cm−2s−1due to lower values of leaf resistance in CO2free air. Transpiration then declined in these leaves due to development of an internal leaf resistance (of up to 2 s cm−1). The internal resistance was masked in leaves at normal CO2concentr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04866.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractSeven‐month‐old rough lemon (Citrus jambhiriLush.) seedlings were subjected to high‐ and low‐humidity treatments (vapor pressure deficits of 8.0 and 19.6 mbar) for 3 weeks. Half of each group was well supplied with water and half was subjected to a series of three drying cycles in which xylem pressure potential fell to below −25 bar. The relationship between leaf conductance and xylem pressure potential was similar during each drying phase and was unaffected by atmospheric humidity. Several days elapsed after rewatering before normal stomatal opening occurred. When all the plants were subsequently kept well watered, leaf conductances decreased as the leaf‐to‐air vapor pressure difference was increased. However, the conductances of previously stressed plants were lower than those of unstressed plants, and consequently previously stressed plants had lower transp

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04867.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractWhen treated with 100 μg/ml (0.57 mM) indole‐3‐acetic acid at pH 4.5,Avena sativacoleoptile segments elongate rapidly at first but begin to shrink after a few hours and eventually approach their initial length. Sufficient quantities of potassium and reducing sugars leak into the medium to reflect a significant change in osmotic potential of the tissues due to solute loss. Plasmometric measurements of subepidermal cell osmotic potentials reveal no alterations in that cell layer due to superoptimal auxin treatments: therefore other cells, presumably those of the epidermis, must be responsible for both the obvious loss of segment turgor and most of the solute loss. The relationship of the change in length to change in volume is the same for segments growing in no auxin, optimal auxin, and superoptimal auxin, indicating that cell swelling in other dimensions is not related to the differences in elongation. The respiration rate in superoptimal auxin falls several hours before the growth slows and stops. This result and the observation that auxin must be accumulated by segments to exert a growth inhibition suggest a site of inhibitory auxin action at or inside of the plasma membrane and not just upon the cell

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04868.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractEmbryogenesis occurred inNigella sativaL. (Fam. Ranunculaceae) leaf callus tissue when coconut milk was replaced from the Murashige and Skoog's (MS) medium by casein hydrolysate. On MS + IAA (0.5 mg/l) + casein hydrolysate (100 and 500 mg/l) medium, tissue gained a capacity of growing embryoids for a pro‐longed culture period. At a concentration of 1000 mg/l casein hydrolysate suppressed the differentiating capacity after the fifth subculture. 2.4‐D and kinetin had inhibitory effects on morphogenesis. Histology of the differentiated tissue revealed that the origin of roots, shoot buds and leaves were from groups of meristematic cells whereas embryoids were initiated by the repeated division of a single c

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04869.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractGrowth of the hemiparasiteRhinanthus serotinus(Schönh.) Oborny was greatly stimulated after attachment of the parasite to the roots of the host plant,Hordeum vulgareL. Before attachment the hydrostatic pressure in the xylem, determined by the pressure bomb technique, was found to be lower inRhinanthusthan in the host. It increased after the formation of haustoria between host and parasite. Apparently, the water transport toRhinanthuswas facilitated. The hydrostatic pressure remained lower than that of the host, accounting for the flow of water and solutes in the direction of the parasite and indicating that there exists a resistance to water transport in the haustoria. Water and solutes were absorbed by the cells, which increased in size. The turgor pressure of the parasite rose steeply, but the osmotic potential was hardly affected

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb04870.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY