摘要:

AbstractA definition of plant hormone sensitivity is proposed which is based on the initial rates of responses at different hormone concentrations. By analogy with enzyme kinetics, it is concluded that simple concentration‐response curves can be described by a function containing three ‘sensitivity parameters’. Objective methods for determining the values of these parameters and for comparing curves are described. These methods are used to describe the responses ofCommelina communisL. stomata to abscisic acid. If certain assumptions are valid, the sensitivity parameters can be assigned physicochemical meanings. To validate the assumptions, certain experimental criteria must be fulfilled and these are disc

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02073.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe wheat germ translation system was programmed with soluble RNA extracted from foliar abscission zones ofPhaseolus vulgaris, These extracts were taken at various times after the induction of abscission. A translation product with a molecular weight of 42 kilodalton (kD) was only present after this treatment, though three other species 32, 27 and 17 kD increased substantially. The isozyme of cellulase with a pi of 9.5 could not be conclusively identified amongst the products though the 32 kD protein is probably chitinase. Comparison of the abscission zone translatable RNA with that from adjacent petiole and stem tissues showed the 17 kD protein developed in all these location. The 42, 32 and 27 kD bands were found predominantly in the zone and petiole.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02074.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractLead migrating through the tissues ofAllium cepaL. was found, by electron microscopy, autoradiography and other methods, to encounter at least three barriers to penetration. The layers of protoderm and hypodermic meristematic cells in the root meristematic zone and the layer of endodermis in the mature root zone were barriers to apoplastic transport. The central zone was a barrier to apoplastic and symplastic transport. It comprises the quiescent centre in the root meristem and the central part of the root cap. The cells of the deepest ground meristematic tissue layers seemed to act as a barrier, which keeps lead away from the procambium. Lead accumulated in roots but it was not uniformly distributed between their various tissues. The largest amount of lead accumulated both in ground meristematic and cortex tissues.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02075.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe lignotuberous malleeEucalyptus behrianaF. Muell, had much lower predawn leaf water potentials (not higher than – 1.2MPa) than other eucalypts (as high as – 0.2MPa), even after extended rain. This led to the expectation that the lignotuber ofE. behrianamight have specific hydraulic characteristics. Keeping the soil around partially defoliated mallces for several days underwater did not raise the water status above the maximum leaf water potential observed under natural conditions. Digging a plant out and placing its roots in water after removal of the soil rapidly increased the water status to a level consistant with other eucalypts. This indicated that the major impedance to water uptake was a component of the soil rather than in the roots or in the lignotuber.Some of the individual mallces had only two major stems or branches. One stem or branch was kept covered throughout the experiments to prevent transpiration. The other stem was subjected to a variety of different conditions in order to modify water loss from it. The transpiring branch affected the water status of the non‐transpiring plant parts. Hydraulic resistances in the shoot and root/lignotuber were determined from differences in the leaf water potential of covered and uncovered branches, at high water flow rates through the plant. Resistances in branches, including the liquid phase component of the leaf, were significantly larger than in root or lignotuber.The total plant hydraulic resistance ofE. behrianawas similar to that of other eucalypts, such asE. paucifloraSieb. ex Spreng. orE. delegatensisR. T. Bak., even though its growth form was different and its natural leaf water potentials were much lower. An osmotic adjustment at the leaf level was observed in the mallee, keeping its bulk leaf turgor in the same range as compared to the other eucalypt sp

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02076.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractPurified xylem cell walls were prepared from isolated xylem bundles of tomato (an inbred line ofLycopersicon esculentumMill, cv. Tiny Tim). Adsorption and exchange experiments were carried out with115Cd2+,82Rb+and82Br−. The application of γ‐ray spectroscopy permitted the simultaneous measurement of several ions applied together. The cell‐wall water volume was shown to be independent of the external pH and solution ionic strength, possibly due to the presence of lignin. The Donnan Free Space (DFS) volume could be determined as a constant 0.15 dm3per kg cell‐wall dry weight. Consequently, the total cell‐wall cation exchange capacity (CEC) could be estimated based on the DFS volume, and amounted to approximately 1000 mol m−3negative charges. The results of Cd2+‐Rb+exchange experiments indicated an apparent CEC value of about 350–450 mol m−3DFS, at external pH ∼ 4. These data are in agreement with earlier reports on xylem wall CEC, and indicate the weak acid characteristics of the charge groups. The rational selectivity coefficient RCdRb, of the cell wall was shown to depend on external ion fractions and ionic strength, with a maximum RCdRbof 450 at ionic Cd2+fraction near 0.3, based at the smallest experimental ionic strength of the external solution. The adsorption of Cd2+, applied at relatively high concentrations, was shown to be stimulated by simultaneous application of hi

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02077.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe response of photosynthesis,Fe, to salinity was examined in two clones ofAgrostis stolonifera, one derived from a salt marsh (SM) and the other from an inland site (IL). The response of young and old leaves was examined over one week of salt treatment and changes in leaf water relations and concentrations of Na+, Cl−and K+ions were also monitored. Sodium+and chloride−concentrations rose much more sharply in the older leaves of both clones andFedeclined to ca. zero by Day 4.Fein the young leaves of the SM clone was unaffected by salt whilst the young leaves of the IL clone showed a 20% reduction inFewithin 24 h of salt application. This decline was due to a decline in stomatal conductance and a reduction in the photosynthetic capacity of the mesophyll and was associated with a greater accumulation of Na+and Cl−ions and loss of K+ions than in the SM clone. The significance of the salt exclusion from the young leaves of the SM clone to its growth on the salt marsh is disc

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02078.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effcct of the transition from fully to partially wetted soil voluine on transpiration rate and hydraulic conductance of mature citrus trees was examined in a 23‐year‐old, coninicrcial, sprinklerirrigated, Shanio u t i orange orchard. I rriga t i on frequency was determined by the rate of water loss from the soil, a s measured by neutron probes. The hydraulic conductance of tlic tree was coniputed from the rclationship between sap flow i n the trunk and leaf water potential. The diurnal valucs of leaf water potential and sap flow shifted towards lower levels as tlie water stored in the root zone was depleted. In the fully wetted soil volume the tree hydraulic conductance remained constant throughout the irrigation period, from June to Novcniber. However, partial wetting of the soil volume (40%) caused a reduction in the hydraulic conductance of the tree. Tlie decreased hydraulic conductance is attributed to tlie permanent interruption of water transport in part of tlie root system. Tlie rcsults of tlie experiment suggest that despite tlie increase of irrigation frequency, partial wetting intensifies water stress in tlie tr

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02079.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA study of the growth of the maritime halophyteAster tripoliumL. has been carried out over a range of salinity treatments. The regression approach to growth analysis using frequent small harvests has been used to allow ‘continuous’ measurement of growth over a period of 36 d. Salinity was applied with the major ions present in ratios typical of those found in seawater. Growth was inhibited in terms of both dry weight production and leaf expansion at salinity levels equivalent to 0.625 strength sea water (full culture solution 300) and above, with the greatest effect being seen in terms of leaf area.Aster tripoliumdid not show increased succulence at high salinity, leaf fresh weight to dry weight ratio in fact declined, whilst leaf fresh weight per unit area remained constant. It should be noted that the plants exhibit low growth rates due to the low light intensity u

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02080.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractMeasurements of tissue ion contents (Na, K and Cl) were carried out at frequent intervals on plants ofAster tripoliumL. grown at a range of salinities for 36 d. Aster tripolium behaved as a typical halophyte showing high levels of inorganic ion accumulation even at low salinities. As salinity increased Na replaced K to a large extent in the shoot but root K was unaffected up to 500 mol m−3external NaCl. Shoot (Na + K) concentration on a tissue water basis was maintained constant in all treatments throughout the experiment, whereas shoot (Na + K) on a dry weight basis showed marked fluctuations in some treatments. An increase in (Na + K) per gram dry weight was, however, accompanied by a parallel increase in fresh weight: dry weight (FW : DW) ratio. Transport of (Na + K) to the shoot per unit root weight changed during the experiment in the manner expected, given the observed changes in shoot relative growth rate and FW : DW to result in a constant shoot (Na + K) concentration on a water basis.Chloride was the major balancing anion in the shoot at high salinity, but never accounted for more than 38% of the (Na + K) found in the root tissue. At all salinities (Na + K) salts accounted for the majority of the measured shoot sap osmotic potential. The interactions between salinity, growth, ion transport and osmotic adjustment are discusse

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02081.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractUptake and transport of Na and K was studied using the radioactive tracers22Na and42K in intactAster tripoliumL. seedlings grown at two salinities CS 10 and CS 100, (containing 10mol m−1and 100 mol m−3Na, respectively, together with other major ions in the proportions found in sea water). At both salinities a much greater proportion of the Na than K taken up by the plant was subsequently transported to the shoot. Most42K fluxes were reduced by about 40% in CS 100 plants relative to CS 10 except root accumulation which increased. Experiments involving changing the salinity from CS 10 to CS 100 showed that42K fluxes remained constant for at least 40 h, indicating that competition with Na for uptake sites was not the cause of the reduced flux in CS 100 plants.22Na fluxes responded immediately to a change in salinity with all fluxes increasing six‐fold when the salinity was raised. When the salinity was lowered, however, root accumulation returned to the level in CS 10 control plants whereas transport to the shoot was inhibited by the previous high salinity treatment, being reduced to only 35% of the rate in CS 10 plants. The time courses of osmotic adjustment and Na accumulation following an increase in salinity were found to be very similar, with sufficient Na being accumulated to account for the observed increase in sap osmotic pre

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1987.tb02082.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY