摘要:

AbstractThe importance of host‐plant resistance of crop plants in the biological control of aphids and the formation of aphid biotypes is discussed. The rapid response of plant breeders to the formation of new aphid biotypes requires detailed knowledge on the mechanism of host‐plant resistance. Current knowledge on the chemical basis of host‐plant resistance to aphids is summarized. Of central importance to this relationship is the aphid‐pectinase plant‐pectin interdependence. Parallels between the mechanism of aphid‐plant and pathogen‐plant attack are pointed out and how aphid bacterial endo‐symbiotes play a central role in host

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603601

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe time during which pollen development is most sensitive to chilling was investigated. Five cultivars of tomato (Lycopersicon esculentumMill.) bearing flower buds at different stages of development were kept at 7°C for 1 week under 12‐h light periods, during which time growth stopped. After returning the plants to minimum temperatures of 18°C, the presence of chromatin in the pollen was assessed daily as the flowers reached anthesis. The results suggested that there are two stages of acute sensitivity to cold during pollen development, each of which results in cold‐stressed plants having pollen empty of chromatin. The first and most sensitive stage is about 11.2 d (SE = 0.3 d) before anthesis, and this is followed by a second stage of sensitivity about 5.6±0.2 d before anthesis. Flowers that had wholly developed under simulated natural temperatures that decreased diurnally from a maximum of 18°C to a minimum of 7°C also had defective pollen, but pollen of normal appearance was regained within 14°d on return to higher temperatures. Plants ofL. esculentum, and a form (LA 1363) of the wild speciesL. hirsutumfrom high altitudes in the Andes, as well as F1 and F3 generations of their hybrid, were grown to the flowering stage at an altitude of 600 m in Hawaii and then grown for a further 30°d at 2000 m, where night temperature was below 10°C. The high altitude environment severely affected the quality of pollen produced and its release from the stamen inL. esculentum, but not inL. hirsutumLA 1363. The results with the hybrids suggested that such tropical mountain environments can be used as a natural phytotron in the selection of chilling resistance that is only expressed in the m

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603604

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractMycochromone, a metabolite produced byMycosphaerella rosigena, inhibits the ATP‐dependent proton translocation and the ATP‐generated electrical potential in pea stem tonoplast‐enriched vesicles, without affecting the H+/K+exchange induced by nigericin or an artificially imposed proton gradient. The inhibition is dependent on the time of pre‐incubation and mycochromone concentration. In addition, mycochromone inhibits the ATP‐dependent proton translocation in radish plasma membrane‐enriched vesicles, though it does not alter ATPase activity (evaluated by hydrolysis of ATP) in either type of plant vesicle. Mycochromone seems to act on the H+channels for proton translocation of the H+‐pumping ATPase localized on plasmalemma and tonoplast, without affecting the catalytic site of A

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603612

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA microcomputer‐based system for the measurement and maintenance of ion concentrations in hydroponic facilities is described. It is based upon the use of ion‐specific electrodes, is entirely automatic, and enables the experimenter to maintain ion concentrations as low as 25 mmol m−3NO3−and K+in hydroponic facilities of relatively low volume (26 dm3). The system enables the operator to store values for ambient temperature, irradiance, and any ion concentrations (including pH) which can be measured by means of ion‐specific electrodes. The components of this system are all available commercially so that the whole unit can readily be assembled. The advantages of the computer control extend to the manipulation and display of colle

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603618

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractTwo types of association between phytochrome and crude membrane fractions from oat (Avena sativaL.) are distinguished and compared, and that which comprises only a small fraction of the total phytochrome in extracts prepared in the absence of added divalent cations (Watson&Smith. 1982b) has been studied in detail. Extraction in the presence of phenylmethylsulphonyl fluoride shows that proteolysis of Pr(the red‐light absorbing form) probably does not account for the lower levels of membrane‐associated phytochrome measured after far‐red light than after red light. Difference spectra of soluble and membrane‐associated phytochrome indicate that the latter is much less susceptible to spectral degradationin vitrothan is the soluble pool. The stoichiometry of association with the membranes is such that for each phytochrome molecule associated after far‐red light there are three associated after red light and it is argued that this stoichiometry is maintained independent of the extraction pH. The characteristics of this photo‐reversible association of phytochrome with membranes are compared to the characteristics of the widely studied light‐induced enhancement of phytochrome pelletabilily that is dependent on electrostatic interaction of phytochrome

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603627

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA series of fluence‐response curves for the binding of phytochrome to membranes in the absence of divalent cations, as described by Watson&Smith (1982), were constructed to demonstrate that the response obeys the law of reciprocity. Analysis of the binding of Pfr(the far‐red‐absorbing form of phytochrome) showed that two Pfrmolecules bind to the membrane for each Pr(the form with an absorption maximum in the red) photoconverted to Pfrin the intrinsic membrane‐bound phytochrome pool. Using this stoichiometry we have been able to model the binding curve of Pr and match the binding data. Prbinding can be simulated if Prbinds only as a consequence of the binding of Pfr, i.e. when Pfris part of a Pr: Pfrdimer. The enrichment of the membranes with Pfras a result of the binding of Pfrwas also accurately simulated. There is no binding cooperativity. Phytochrome binding is a low‐fluence response and the possibility that it has physiological significance as a mediator of phytochrome action is

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603633

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAxenicLemna minorplants, which form numerous calcium oxalate crystals, were exposed to [14C]‐glycolic acid, ‐glyoxylic acid, ‐oxalic acid and ‐ascorbic acid and prepared for microautoradiography by a technique that preserves only insoluble label to determine specifically the pathway leading to oxalic acid used for crystal formation. Label from glycolic, glyoxylic, and oxalic acids was incorporated into crystals. Label from oxalic acid was also found in starch when exposure to label was done in the light but not dark, while plastids specialized for lipid storage were heavily labelled under both conditions. Incorporation of label from glycolic and glyoxylic acids, but not oxalic acid, was inhibited in the presence of the glycolate oxidase inhibitors, αHPMS (2‐pyridylhydroxy methanesulphonic acid) and mHBA (methyl 2‐hydroxy‐3‐butynoic acid), and inhibition of labelling was not due to an effect on uptake. These studies show that the glycolate oxidase pathway to oxalic acid is operational inL. minorand that the product is available for crystal formation. Dark‐grown plants form almost four times as many crystal cells (idioblasts) as do light‐grown plants, indicating crystal formation is not in response to photorespiratory glycolate production. Label from [1‐14C]ascorbic acid was also incorporated into crystals and labelling was inhibited by mHBA, indicating glycolic acid and/or glyoxylic acid are possible intermediates of ascorbic acid catabolism.The effect of nitrogen source on crystal formation was also investigated. Significantly more crystal idioblasts were formed, on a surface area basis, by plants grown on ammonium than by plants grown on nitrate nitrogen. When grown with mixed ammonium and nitrate, an intermediate number of crystal

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603639

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAssociations between photosynthetic responses to CO2at rate‐saturating light and photosynthetic enzyme activities were compared for leaves of maize grown under constant air temperatures of 19, 25 and 31°C. Key photosynthetic enzymes analysed were ribulose bisphosphatc (RuBP) carboxylase, phosphoenolpyruvate (PEP) carboxylase, NADP‐malic enzyme and pyruvate, Pidikinasc. Rates of CO2‐saturated photosynthesis were similar in leaves developed at 19°C and 25°C but were decreased significantly by growth at 31°C. In contrast, carboxylation efficiency differed significantly between all three temperature regimes. Carboxylation efficiency was greatest in leaves developed at 19°C and decreased with increasing temperature during growth. The changes of carboxylation efficiency were highly correlated with changes in the activity of pyruvate, Pidikinase (r= 0.95), but not with other photosynthetic enzyme activities. The activities of these latter enzymes, including that of RuBP carboxylase, were relatively insensitive to temperature during growth. The sensitivity of quantum yield to O2concentration was lower in leaves grown at 19°C than in leaves grown at 31°C. These observations support the novel hypothesis that variation in the capacity for CO2delivery to the bundle sheath by the C4cycle, relative to the capacity for net assimilation by the C2cycle, can be a principal determinant of C4photosynthetic resp

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603649

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe symbiosis between a bacterium and the West African rain forest yamDioscorea sansibarensisis described for the first time at the ultrastructural level. The bacteria are harboured in glands which run the entire length of the pronounced ‘drip‐tip’ leaf acumenae of the host plant. Each acumen, which may be up to 12 cm long in very large mature leaves, contains from two to six bacterial glands. The glands are kidney‐shaped in cross section and contain numerous multicellular simple trichomes which arise from the epidermis of the gland floor and project into the lumen of the gland. The bacteria are Gram‐negative and variously rod, ovoid, and coccoid in shape. The bacterial cells contain mesosomes, polyhydroxybutyrate granules and large electron‐dense bodies. Bacteria‐free plants grow more slowly and produce one yellowish‐green leaf per node in contrast to the vigorous growth habit of infected plants, with two deep green leaves per node. Infected plants exposed to a variety of atmospheres containing acetylene, both in the light and in the dark, failed to reduce acetylene to ethylene, indicating that nitrogen fixation is not a function of

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603654

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA field portable system is described which measures the response of gas exchange of one leaf to changes in environmental parameters under controlled conditions, and which simultaneously measures the gas exchange of another leaf as the climatic parameters vary naturally. The system consists of two independently operating cuvettes. It enables detailed studies of photosynthesis and stomata/transpiration of leaves attached to the plant in their natural position. It provides control of temperature, humidity, CO2and oxygen concentration (or, alternatively, of other gases) as well as of light. Infrared gas analyzers for CO2and H2O are used which allow similar time constants for the measurement of the two gases.Examples of a diurnal course of gas exchange of a leaf in its natural exposition and of experiments with steady‐state responses of gas exchange are presented. InEucalyptus paucifloraSieb. ex Spreng. ssp.pauciflora, a set of response curves of CO, assimilation (A) to CO2, as measured at various leaf temperatures and light levels, shows carboxylation efficiency to be light saturated at the lower photon irradiances the lower the leaf temperature is. Carboxylation efficiency is maximal at 25°C. At ambient CO, partial pressure stomata open in a way that CO2assimilation occurs at a rate found within the curvature region of the CO2response function ofA.The light‐independent CO2compensation point as a function of temperature is presented.Applying a combined heat/low humidity pulse (15 or 60 min) on leaves ofEucalyptus behrianaF. Muell. orPinus radiataR. Don, respectively, leads to a lower level of intercellular carbon dioxide partial pressure (Ci) during the decline in A and leaf conductance to water vapour (g). A lowerCilevel is maintained during recovery ofAandg, Aalmost reaching the pre‐pulse level but notg.The existence of an after‐effect indicates that the response to the combined high temperature/low humidity pulse is a multi‐st

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11603690

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY