摘要:

AbstractThe dynamic response of stomata to changes in atmospheric humidity was investigated inFragaria × ananassaDuch.,Picea engelmannii Parry, andPseudotsuga menziesii(Mirb.) Franco; and the effect of water stress on this response was determined inPseudotsuga menziesii.The plants were rotated through three regimes of ambient temperature and vapour pressure deficit: 35°C–3. 5kPa, 35°C–0. 5 kPa, and 20°C–1. 5kPa. Branch and leaflet conductance were measured with a steady‐state porometer, first at ambient vapour pressure deficit and then at one of four treatment conditions achieved by increasing or decreasing vapour pressure within the porometer cuvette. All three species showed similar stomatal response: enhanced conductance at low vapour pressure deficit and depressed conductance at high vapour pressure deficit. Engelmann spruce was more sensitive than Douglas fir and strawberry.Plant water status significantly altered stomatal response to vapour pressure deficit. The relationship of conductance of xylem water potential was linear under ambient conditions but became curvilinear when conductance was measured above and below ambient vapour pressure deficit. Between −0. 5 MPa and −2. 0 MPa xylem water potential, the stomata were sensitive to vapour pressure deficit, but below − 2. 0 MPa, the sens

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588103

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

1The hydraulic conductance of roots of chilling‐sensitive mung bean plants is reduced markedly at low temperatures. When roots are chilled suddenly under high irradiance, or when plants with roots chilled in the dark are exposed to a natural dawn, the stomata remain open for several hours. During this period the plants may wilt severely if the evaporative demand is sufficiently large. Under lower evaporative demand and less severe wilting, the plants may subsequently rehydrate.2Following root chilling there is a rapid (>30 min) initial change in root conductivity (3. 2‐ fold).3Within hours the hydraulic conductivity of the pathway from stem xylem to leaf tissue decreases dramatically.4Within 1 d, the hydraulic conductivity of the roots decreases further (4. 5‐fold).5Over 5 d these large resistances disappear and conductivity recovers to a value greater than at the start of chilling. This response and stomatal closure allow the plant to rehydrate to a condition similar to that of controls.6There is no simple relation between this hydraulic recovery and the accumulation of abscisic acid in the

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588106

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractIn conformity with earlier results, low‐temperature hardening of cabbage seedlings lowered the osmotic potential and increased the permeability to thiourea of the petiole cells. It also decreased the time required for rounding‐up of the protoplasts in cells plasmolysed in 1. 5 × isotonic (or higher) glucose or CaCl2solutions.Solutions of dimethylsulphoxide (DMSO), thiourea, urea, and glycerol each accelerated the rate of rounding‐up of protoplasts in plasmolysed cells, compared to the rate in glucose solution of the same hypertonicity. Each also penetrated the cell membranes as indicated by deplasmolysis. Only in the case of DMSO, in which there was very rapid deplasmolysis (5–6 min), was this rounding‐up due to protoplast expansion. In the case of thiourea (deplasmolysis within 30–60 min) rounding‐up occurred almost immediately (less than 2 min), before protoplast expansion was sufficient to induce it. It was concluded that the accelerated rounding‐up was due to a rapid osmotic adjustment in the protoplasm by the penetrating solution, which increased its water content and decreas

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588112

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractAfter germination, pollen grains ofLilium longiflorumbecame very sensitive to short periods of heat stress as shown by the greatly reduced germination percentages upon subsequent incubation at the optimal temperature. Addition of proline to the incubation medium made pollen more resistant to heat. It was demonstrated that in a short time a large amount of proline was taken up by the cell. Germination and metabolic functions were completely or partially protected from heat damage by proline treatment. As well, it was shown that proline treatment at least partially protected pollen grains from cold stress. These results suggest that the high proline concentrations found in pollen of many species may confer resistance to germinating pollen grains at unfavourable temperatures thereby enhancing the chances of successful fertilization.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588117

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractMechanisms of plant protection and acclimation to potentially damaging solar ultraviolet‐B (UV‐B, 280–320 nm) radiation incident on the Earth's surface were examined inOenothera stricta. Attenuation of this radiation in the upper leaf epidermis reduces the penetration of UV‐B radiation to the mesophyll where damage to physiologically sensitive targets can occur. The epidermis is a highly selective radiation filter that can attenuate up to 95% of the incident UV‐B radiation and yet transmit between 70% and 80% of the visible radiation. Exposure to UV‐B radiation significantly reduced the degree of epidermal UV‐B transmittance by as much as 33%. No significant reduction in epidermal transmittance of visible radiation was observed as a result of UV‐B exposure. The plasticity in epidermal UV‐B transmittance results from production of flavonoid and related phenolic compounds in the tissue. Absorbance of UV‐B radiation in llavonoid extract solutions from epidermal and mesophyll tissues significantly increased by as much as 100% and 35%, respectively, after exposure to UV‐B radiation. Photosynthetic rates of leaves exposed to UV‐B radiation were not significantly reduced at dose rates representative of the radiation flux found in the habitat of this species, but significant photosynthetic depression was observed at dose rates that exceed the field UV‐B flux. The phenotypic plasticity in epidermal UV‐B transmittance resulting in decreased penetration of damaging UV‐B radiation to the mesophyll may reduce the rate of damage to a level where repair mechanisms can

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588121

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractTransmission electron microscopy of chloroplasts isolated by osmotic lysis of pea leaf protoplasts has revealed crystalline arrays of ribosomal particles associated with the thylakoid membranes. Optical diffraction techniques have established the crystallinity of the arrays and an image‐enhancement technique has given an indication of ribosomal macrostructure. A model of crystal‐packing is presented. This apparently artefactual induction of ribosome crystals should provide a valuable approach towards the elucidation of the details of the structure of chloroplast riboso

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588124

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe transition from primary dormancy to secondary dormancy was examined using upper cocklebur (Xanthium pennsylvanicumWallr.) seeds. The non‐after‐ripened seeds with primary dormancy responded to chilling, anoxia, KCN, and NaN3with an increase in germination. However, their maximal responses to these treatments only occurred after a period of water imbibition, probably a reflection of the increasing growth potential of the axial tissue which was accompanied by the increase in the capacities of respiration and ethylene production. On the other hand, the establishment of secondary dormancy was accompanied by a decrease in respiration and ethylene production of seeds, and in the growth potential of both axial and cotyledonary tissues. The decrease in growth potential of these tissues occurred regardless of whether they were excised from after‐ripened seeds or non‐after‐ripened seeds. It is inferred that the primary dormancy of cocklebur seeds is a state maintained in un‐germinated seeds for a long time through a spontaneous transition to seconda

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588130

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractSalt‐stimulated ATPase activity in membrane preparations obtained from roots ofAtriplex nummulariaLindl. at pH 5 was not suscep‐tible to inhibition by KC1 or NaCl up to 450 mol m‐3 but showed a broad peak of activity between 150 and 300 mol m−3. At pH 8 stimulation occurred at 50 mol m−3but concentrations above 100 mol m−3depressed activity below the level of the MgATPase activity. By contrast, preparations from roots ofPisum sativumL. at pH 5 showed maximal stimulation at 25 to 50 mol m−3of NaCl or KC1; concentrations higher than 150 mol m−3depressed activity below that of MgATPase activity. At pH 8 maximal stimulation was observed at 5 to 10 mol m−3NaCl or KC1 while the threshold for inhibition was reduced to 15 mol m−3. With increasing salt concentrations the pH profiles for NaCl stimulation ofAtriplexATPase activity (expressed as the difference between treatment and control) showed a progressive displacement of the apparent optimum towards lower pH. The shift was not apparent when stimulation was expressed as a percentage of MgATPase activity. This shift may be accounted for if NaCl stimulated the monovalent salt‐activated ATPase activity but simultaneously inhibi

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588131

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe production, growth, and development of the abscisic‐acid‐induced turion (a small dormant bud) ofSpirodela polyrrhizawere investigated. Addition ofABAto a culture ofS. polyrrhizaresulted in growth inhibition at concentrations as low as 10−6molm−3, growth being completely arrested at 10−2mol m. Over a single order of magnitude range around I0−4molm−3,ABAalso induced the production of turions. The range of turion‐producing concentrations ofABAwas found to be much narrower than previously reported, turion production having a clearly defined threshold, optimum, and upper limit. The possibility that growth inhibition and turion formation are integrally linked aspects of a single response is discussed. Only primordia ≤0.7 mm long at the time ofABAaddition could be induced to develop into turions and the events leading to turion formation were found to be reversible up to 72 h inABA. It is concluded thatin terms of turion formationthere is a sensitivity window to abscisic acid lasting some 4–20h in the normal developmental life of frond cells. Providing cells experience the appropriate signal in this sensitivity window they initiate a new programme which eventually leads to turion formation. Microscopical analysis showed that the cells within this sensitivity window were still actively dividing. It is suggested that the developmental switch‐over to rapid cell expansion and separation marks the end of this

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588135

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe ultrastructural features of the abscisic‐acid‐induced turion ofSpirodela polyrrhizaare briefly described and a comparison between turion and vegetative frond tissue was made by stereological analysis. The turion is characterized by its small size, reniform shape, and dark‐brown coloration; the mesophyll is undifferentiated and totally lacking the substantial acrenchyma development found in the vegetative frond. The turion cells have a smaller vacuole and a denser cytoplasm than the cells of the vegetative frond. Stereological analysis showed that the tissues differed quantitatively only in three main respects: air space formation, vacuolation, and starch and cell wall material accumulation. During development, it is suggested that the cells of the turion, while reaching the same final size as the vegetative frond cells, accumulate numerous starch grains, thick cell walls, and large deposits of tannins and anthocyanin pigment at the expense of the vacuolar expansion characteristic of the normal maturity programme. Certain features of the turion ultrastructure indicate a differential cell sensitivity t

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588143

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY