摘要:

AbstractI suggest that action potentials, which occur in most, if not all, plants, play a major role in intercellular and intracellular communication. Long‐distance communication is achieved through the transmitted changes in membrane potential, whereas local signalling is achieved through changes in the subcellular localization of ions (K+, Cl−, and Ca2+) and of water, and perhaps by membrane depolarization and current flow. These local changes in ion concentration can lead to modified activities of enzymes in the cell wall (e.g. pectinase), the plasma membrane (e.g. cellulose synthetase, callose synthetase), and the cytoplasm (e.g. protein kinase). In particular, the elevated concentration of cytoplasmic Ca2+is shown to have a major, yet complex, role, especially in the modulation of translation. I suggest further that, in addition to their role in wounding, action potentials may also be important signalling mechanisms for chilling injury, mechanical perturbation and invasion by pathogens, as well as for light and grav

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01844.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAerobically germinated seedlings of rice andEchinochloawere found to survive when placed in an anaerobic environment for 4 d, whereas pea and maize seedlings did not. Although root and shoot growth were inhibited in rice andEchinochloaunder anaerobiosis, growth resumed when the seedlings were returned to aerobic conditions. Alcohol dehydrogenase (ADH) activity increased more, and protein synthesis was greater, in the shoots than in the roots under anaerobic conditions. These results suggest that, in anaerobiosis‐tolerant species, ADH activity and protein synthesis in the shoots represents or results from metabolic adaptations to low oxygen. These results are discussed in terms of plant establishment and growth in a low‐oxygen environm

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01845.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractWater flow and water storage were investigated forAgave deserti, a desert succulent showing crassulacean acid metabolism (CAM). The anatomy and water relations of the peripheral chlorenchyma, where CAM occurs, and the central water‐storage parenchyma were investigated for its massive leaves so that these tissues could be incorporated as discrete elements into an electrical‐circuit analogue of the whole plant. The daily cycling of osmotic pressure was represented by voltage sources in series with the storage capacitors. With soil water potential and leaf transpiration rate as input variables, axial water flow through the vascular bundles and radial flows into and out of storage during the day/night cycle were determined.The predominantly nocturnal transpiration was coincident with increases in cell osmotic pressure and in titratable acid of the leaf chlorenchyma. In the outer layers of the chlorenchyma, water potential was most negative at the beginning of the night when transpiration was maximum, while the water‐storage parenchyma reached its minimal water potential 9 h later. The roots plus stem contributed 7% and the leaves contributed 50% to the total water flow during maximal transpiration; peak water flow from the soil to the roots occurred at dawn and was only 58% of the maximal transpiration rate. Over each 24‐h period, 39% of the water lost from the plant was derived from storage, with flow into storage occurring mainly during the daytime. Simulations showed that the acid accumulation rhythm of CAM had little impact on water uptake from the soil under the conditions employed. In the outer chlorenchyma, water potential and water flows were more sensitive to the day/night changes in transpiration than in osmotic pressure. Nevertheless, cell osmotic pressure had a large influence on turgor pressure in this tissue and determined the extent to which storage was recharged during the latter part of th

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01846.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractLeaf diffusion resistance and leaf water potential of intactSolanum melongenaplants were measured during a period of chilling at 6 °C. Two pretreatments, consisting of a period of water stress or a foliar spraying of abscisic acid (ABA), were imposed upon the plants prior to chilling. The control plants did not receive a pretreatment. In addition to intact plant studies, stomatal responses to water loss and exogenous abscisic acid were investigated using excised leaves, and the influence of the pretreatment observed. Chilled, control plants wilted slowly and maintained open stomata despite a decline in leaf water potential to –2.2 MPa after 2 d of chilling. In contrast plants that had been water stressed or had been sprayed with abscisic acid, prior to chilling, did not wilt and maintained a higher leaf water potential and a greater leaf diffusion resistance. In plants that had not received a pretreatment, abscisic acid caused stomatal closure at 35 °C, but at 6°C it did not influence stomatal aperture. The two pretreatments greatly increased stomatal sensitivity to both exogenous ABA and water stress, at both temperatures. Stomatal response to water loss from excised leaves was greatly reduced at 6°C. These results are discussed in relation to low temperature effects on stomata and the influence of preconditioning upon plant water rela

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01847.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractLight is used commercially to prevent the sprouts on seed potatoes from growing so long that they are knocked off at planting. We investigated the relationship between wavelength and growth inhibition, using a very long irradiation time of 23 d with a 12‐h photoperiod. The inhibition showed a narrow peak of far‐red activity centered on 707 nm, with a shoulder in the red whose size depended on the degree of inhibition chosen as standard, because the log photon‐fluence rate/response lines were not parallel. There was also inhibitory activity in the blue (<500 nm). In many respects the wavelength relationship resembled the action spectra for growth inhibition in dark‐grown seedlings, but in the latter the red peak is, or quickly becomes, more pronounced than the far‐red peak: this did not happen with potato sprouts. Blue light caused a positive phototropic response at similar or lower fluence rates. Greening became visible only at the highest fluence rates, between the two spectral regions inhibitory to growth. Broadband sources had much less inhibitory activity in the 650–75

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01848.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe nature of the solutes accumulated in the grains of ten finger millet genotypes grown under rain‐fed conditions with moisture stress during panicle and grain development were determined. Although grain yield decreased under stress, the solute potential (SP) of seeds from stressed plants was significantly lower (more negative), probably due to the increase in sucrose content. There were no significant changes in the content of total amino acids, free proline, reducing sugars or potassium. The contribution of sucrose to total solute potential was approximately 32% in seeds obtained from stressed plants as compared with only 15% in seeds from irrigated treatment. The germinability and seedling vigour of the seeds from stressed plants was significantly higher under simulated stress with polyethylene glycol (PEG), but was similar to that of seeds of non‐stressed plants under normal conditi

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01849.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAn experimental system has been developed for studying efflux of14C assimilates in growing potato tubers. Small wells are cut into the phloem‐rich perimedulla and filled with trap solutions of varying composition which inhibit or promote assimilate efflux. One well on each tuber acts as the treatment while a second well acts as the control. Movement of14C into wells occurred at comparable rates to that found in intact tissue, harvested from importing tubers in the form of microcores. Sucrose was the predominant translocated sugar in the stolon and was not hydrolysed in either the wells or the microcores following unloading. Efflux into wells containing agar traps was stimulated 40‐fold relative to buffer controls by the addition of 20 mol m−3EGTA to the agar. This was interpreted as passive efflux to the apoplast due to increased membrane permeability in the pathway between the sieve elements and the collecting wells. The EGTA stimulation was reversed by addition of Ca2+.14C efflux into buffered solutions was inhibited significantly by both DNP and PCMBS, suggesting the involvement of active and carrier‐mediated transport components. However, it was not possible to determine whether these compounds acted at the site of unloading only, or on the short‐distance transfer step between phloem and collecting wells. The rate of tracer efflux was not significantly different when 1 mol m−3and 300 mol m−3sucrose were applied to the wells, indicating insensitivity of solute movement to low apoplastic solute concentrations. However, raising the solute concentration to 800 mol m−3caused a severe inhibition of tracer efflux. These results were duplicated with mannitol as the osmoticum. It is suggested that plasmolysis prevented further efflux by disruption of a predominantly symplastic transport pathway between the phloem and c

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01850.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractSmall discs punched out from leaves of tobacco (Nicotiana tabacumL.) were exposed for 3 min in the dark to a high temperature of around 48°C. This caused a progressive inhibition of the gas‐exchange (oxygen evolution) type photoacoustic signal, resulting‐ finally in phase inversion (i.e. leading to negative values), which indicates that oxygen uptake replaces the normal oxygen evolution. This effect was also observed in various other plant species. Oxygen uptake was rapidly reversed (within ca. 4–5 min) to a certain low value of oxygen evolution (about 20% of the control) by continuous illumination with relatively strong white light (minimum 55 W m−2). However, a few minutes in darkness following this heat treatment induced reappearence of the uptake signal. This photoacoustically detected oxygen uptake after heat shock may be interpreted as reflecting stimulated oxygen photoreduction (Mehler reaction) caused by (light dependent) inactivation of the Calvin cycle by heat, suggesting that oxygen may act as a major photosynthetic electron acceptor under stress conditions. Leaves suffering from such heat shock effects were completely restored to normal behaviour after a 24‐h incubation at room temperature (25 °C). Analysis of the modulation frequency and wavelength dependence of the photoacoustic signals showed that heat shock‐induced oxygen uptake is a very complex phenomenon, composed of at least two components differing in kinetics and sensit

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01851.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractChanges in the net uptake rate of K+and in the average tissue concentration of K+were measured over 14 d in response to changes in root temperature with oilseed rape (Brassica napusL. cv. Bien venu) and barley (Hordeum vulgareL. cv. Atem). Plants were grown in flowing nutrient solutions containing 2.5 mmol m−3K+and were acclimatized over 49 d (rape) or 28 d (barley) to low root temperature (5°C) prior to steady–state treatments at root temperatures between 3 °C and 25 °C, with common air temperature. Uptake of K+was monitored continuously over 14 d and nitrogen was supplied as NH4++ NO−3or NH+4or NO−3. Unit absorption rates of K+increased with time and with root temperature up to Day 4 or 5 following the change in root temperature. Thereafter they usually approached steady‐state, with Q10≃ 2.0 between 7 °C and 17°C, although rates became similar between 7 °C and 13°C. Uptake of K+by rape plants was invariably greater under NO−3nutrition compared with NH+4. The percentage K+in the plant dry matter increased with temperature from 2% at 3 °C to 4% at 25 °C in rape, but there was less effect of temperature on the average concentrations of K+in the plant fresh weight or plant water content. Concentrations of K+in the leaf water fraction of rape plants decreased with increasing root temperature, but in barley they increased with increasing root temperature. Concentrations of K+in the root water fraction were relatively stable with respect to root temperature. The results are discussed in terms of compensatory changes in K+uptake following a change in root temperature and the relationships between growth, shoot: root ratio and K+co

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01852.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe contribution from temperature gradients within a plant to convective transport is calculated. Its magnitude depends primarily on the temperature differences in the plant and the radius of the conducting elements; the other quantities affecting it are well‐established physical constants. Assuming a temperature difference in the plant of 1 K and a conductive element radius of 10−4m, the speed of convective flow is 0.5 cm h−1and this is independent of dis

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb01853.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY