摘要:

AbstractThe leaves ofBerberis aquifolium(Pursh.) exhibit either diffuse or specular (shiny) reflection, depending on the variety, but in no case are the leaves obviously glaucous. The dull‐surfaced leaves were less wettable than the glossy ones. Using scanning electron microscopy it was determined that the diffuse reflection was due to tubular crystals of wax 250 nm in diameter. The crystals were primarily composed of 19‐nonacosanol, a 29‐carbon secondary alcohol, as determined by gas chromatography‐mass spectrometry. The chemical constituents of the wax underlying the tubes appeared to be the same as those of the wax from glossy leaves, with 29‐carbon and 31‐carbonn‐alkanes andn‐heptacosanol as major constituents. The reflection spectra of dull‐surfaced (diffuse reflection) or glossy (specular reflection) leaves were the same, as were those of leaves with different amounts of epicuticular wax. Removing the epicuticular wax with chloroform did not ch

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611670

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper describes a dynamic model for photosynthesis by an aquatic plant,Egeria densa.The model takes into account an HCO−3pump, high diffusion resistances and PEP carboxylase, and develops a set of differential equations to form the time‐dependent solutions for photosynthesis. The predicted changes in pH, [CO2]aqand total inorganic carbon are compared with experimental data and the model is found to describe the data.The model is then used to examine the effect of O2on photosynthesis under these conditions, and shows that the increase in internal CO2concentration due to the recycling of photorespiratory CO2directly stimulates gross CO2fixation and can more than compensate for the O2inhibition of gross photosynthesis. The importance of the HCO−3pump in O2inhibition is also examined.The CO2compensation point (where inorganic carbon influx and efflux are equal) is examined and the importance of the HCO−3pump and PEP carboxylase in reducing the compensation concentration is discussed.The model was developed in order to study the photosynthesis of an aquatic weed, which will be reported in a late

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611677

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe effect that the massive presence of lichen thalli growing on the branches ofQuercus pyrenaicaandQ. rotundifolialeaves has on their chloroplasts been studied. In both species there were significant decreases in the amount of chlorophylls in the leaves of twigs with a dense cover of lichens in comparison with the leaves from thallus‐free twigs. The areas and perimeter of chloroplasts in leaves from twigs with epiphytes did not differ significantly from those in leaves without epiphytes. However, in leaves with epiphytes the percentage of chloroplast area occupied by starch was higher. InQ. pyrenaicathe number of grana per chloroplast section and per μm2, the percentage of chloroplast stroma occupied by grana, the average number of thylakoids forming grana and the grana width was significantly smaller in leaves near lichen populations. These results are discussed and related to the great chelating capacity of the lichen's substanc

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611691

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIndividual leaves and stems were analysed for Na+, Cl−, K+and water content in two clones ofAgrostis stoloniferadiffering in salt resistance, during 14 d of treatment with NaCl, 100 and 200 mol m−3, and a further 7 d in a salt‐free medium. Great differences in ion and water content were revealed between individual organs, and organ‐by‐organ analysis also emphasized the differences between the clones better than whole shoot analysis. In both clones, Na+and Cl−accumulated to the greatest degree in the older leaves, but for corresponding organs, the concentrations were lower in the more tolerant clone. In the sensitive clone, the lowest leaves dehydrated in 200 mol m−3NaCl and failed to recover, while the plants of the more resistant clone maintained viable water content in all organs. In the resistant clone, K+concentration decreased less in response to salt treatment than in the more sensitive clone. For a full appreciation of the plants' reactions, it was found necessary to express the analytical data on several bases, namely, per unit dry‐weight, unit water, and to

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611707

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe time course of loading and transport of assimilate in sunflower leaves was examined by pulse labelling with14CO2, followed by freeze drying or freeze substitution, and dry autoradiography at both low and high resolution. The five classes of veins, V1‐V5 (V5 being smallest), show a division of function: V5 and V4 are engaged in loading and short distance transport; V3 to V1, in long distance translocation. The first high concentration of14C is found in two or three phloem parenchyma cells (intermediary cells) of V5 and V4 veins. The sieve elements of V5 and V4 veins do not show comparable concentrations of14C at any time. Recently assimilated14C is transported by the intermediary cells for distances of about 0.5 mm to the V3 veins. In V3 to V1 veins translocation is in the sieve tubes. Transport in V5 and V4 veins is in two directions, that in V3 to V1, in one direction towards the petiole. The high concentration of14C formed in the intermediary cells does not increase further as the assimilate moves to the sieve tubes of the V3 veins, and so is probably the origin of the gradient that drives translocatio

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611718

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe free 4‐desmethylsterol composition of plasma‐membrane‐enriched preparations from white fibrous roots of Rangpur lime(Citrus reticulatavar.austerahybrid?), Kharna khatta (C.kharnaRaf.) and Etrog citron(C. medicaL.) seedlings grown in the presence of 0, 50, or 100 mol m−3NaCl for 28 d was quantitated by gas chromatography (GC) on analytical capillary (SE‐54 fused silica) columns and the sterols were identified by combined gas chromatography‐mass spectrometry (GC‐MS).Only three 4‐desmethylsterols were positively identified by GC‐MS, viz. campesterol, stigmasterol and sitosterol. Cholesterol could not be positively identified in any of the membrane preparations. Campesterol levels were generally similar for all treatments and for all three genotypes, approximating 30% of the total free 4‐desmethylsterol content of the plasma membranes. At all levels of salinity (0, 50 or 100 mol m−3NaCl) sitosterol levels decreased in the order Rangpur lime>Kharna khatta>Etrog citron and stigmasterol levels decreased in the reverse order. The ratio of sitosterol to stigmasterol was highest in Rangpur lime and lowest in Etrog citron at each level of salinity and was reduced by salt treatment in all three genotypes.Salt‐induced reductions in the ratio of ‘more planar’ to ‘less planar’ sterols correlated inversely with the accumulation of Cl−in the leaves of the three genotypes suggesting a role for plasma membrane sterols in the Cl−exclusion mechanism. A model relating sterol structure, membrane sterol composition and membrane permeability to Cl−exc

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611800

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFibrous roots of four citrus hybrids and parent rootstocks from which the hybrids were generated, all selected for their different Cl−exclusion abilities, were assayed for phospholipid, galactolipid and free 4‐desmethylsterol content. There was no correlation between a plant's ability to exclude Cl−and the level of either phospholipid, galactolipid, or total free sterol in the roots of control plants. However, an inverse correlation was established between the ratio of phospholipid to free sterol in control roots and total leaf Cl−levels of plants treated with 50 mol m−3NaCl for 56 d.With the exception of a significant decrease in hybrid 80‐05‐05, galactolipid levels were unaffected by salt treatment. Phospholipid levels were significantly increased in two parent rootstocks viz. Trifoliate orange (Poncirus trifoliata(L.). Raf.) and Carrizo citrange (Citrus sinensis(L.) Osbeck ×P. trifoliata) and one hybrid (80‐02‐08) but were otherwise unchanged by salt treatment. Free sterol levels were significantly increased by salt treatment in all of the better Cl−excluders except Carrizo citrange i.e. in Rangpur lime (Citrus reticulataBlanco var.austerahybrid?), Cleopatra mandarin (Citrus reticulataBlanco) and all hybrids except 80–05–13. In all genotypes examined, salt‐treatment resulted in a significant decrease in the ratio of sitosterol to stigmasterol reflecting, primarily, an increase in the stigmasterol level. The two poorer Cl−excluders (Trifoliate orange and hybrid 80–05–13) both underwent a significant decrease in the ratio of ‘more planar’ to ‘less planar’ sterols.The inverse correlation between the phospholipid to free sterol ratio of control plants and leaf Cl−level of salt treated plants suggests that this ratio has the potential to be used as a biochemica

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611810

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractField gas exchange measurements on intact peach(Prunus persica(L.) Batsch) leaves indicate that leaf nitrogen content (NL) and leaf weight per unit leaf area(Wa)are highly correlated with CO2assimilation rate(A)and mesophyll conductance (gm). Therefore, NLand Wawere used to study seasonal relationships between leaf carboxylation capacity and natural light exposure in tree canopies. From mid‐season onwards, NLandWawere linearly correlated with light exposure expressed as the amount of time during a clear day that a leaf was exposed to a photosynthetic photon flux density (Q) of ≥ 100 μmol m−2s−1. The data support the hypothesis that whole‐tree photosynthesis is optimized by partitioning of photosynthetic capacity among leaves in deciduous tree canopies with respect to natural ligh

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611823

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractChenopodium albumL. plants, grown under controlled environmental conditions on different levels of soil nitrate, produced seeds with proportionately different NO−3contents. Regardless of the endogenous NO−3content, few seeds germinated in water or upon treatment with KNO3. Ethylene promoted germination, and the extent of germination was positively correlated with the endogenous seed NO−3content. Combined application of ethylene and KNO3in the dark had a synergistic effect on NO−3‐deficient seed. The synergism between ethylene and KNO3was attributable to the NO−3moiety of the nitrate salt. Ethylene and light showed moderate synergism in seeds with low or high endogenous nitrate. Addition of nitrate, however, masked the interaction between ethylene and light. Gibberellic acid4+7(GA4+7) or red light, each alone or combined with KNO3, had little effect on germination. When applied together in the dark, ethylene and GA4+7synergistically enhanced the germination of NO−3‐deficient seed. The combined effects of the two hormones on this seed were further enhanced by the addition of KNO3. There was no synergism between ethylene and GA4+7in NO−3‐rich seed. These interactions among GA4+7, ethylene and KNO3were not affected by light. The results confirm and further elaborate our earlier finding that the sensitivity ofC. albumseeds to ethylene may depend on n

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611829

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractGrowth‐chamber cultivatedRaphanusplants accumulate nitrate during their vegetative growth. After 25 days of growth at a constant supply to the roots of 1 mol m−3(NO−3) in a balanced nutrient solution, the oldest leaves (eight‐leaf stage) accumulated 2.5% NO−3‐nitrogen (NO3‐N) in their lamina, and almost 5% NO3‐N in their petioles on a dry weight basis. This is equivalent to approximately 190 and 400 mol−3m−3concentration of NO−3in the lamina and the petiole, respectively, as calculated on a total tissue water content basis. Measurements were made of root NO−3uptake, NO−3fluxes in the xylem, nitrate uptake by the mesophyll cells, and nitrate reduction as measured by anin vivotest. NO−3uptake by roots and mesophyll cells was greater in the light than in the dark. The NO−3concentration in the xylem fluid was constant with leaf age, but showed a distinct daily variation as a result of the independent fluxes of root uptake, transpiration and mesophyll uptake. NO−3was reduced in the leaf at a higher rate in the light than in the dark. The reduction was inhibited at the high concentrations calculated to exist in the mesophyll vacuoles, but reduction continued at a low rate, even when there was no supply from the incubation medium. Sixty‐four per cent of the NO−3influx was turned into organic nitrogen, with the remaining NO−3accumu

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11611835

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY