摘要:

External application of abscisic acid (ABA) induces a relatively high rate of xylem exudation in excised roots ofLupinus luteusL. cv. Weiko III. The response is relatively slow with a lag period of ca 1 h. It is also slowly, but reversibly, abolished by application of 3.6 or 36 μMcycloheximide (CHX). Contrary to expectation, K+is not a significant factor in maintaining flow rates in lupin roots as no response was measured after adding K+to root systems, from which K+had been withheld for periods ranging from 3 h to several days. In fact, excised roots obtained from seedlings raised in the absence of K+failed to respond to added K+. Total depletion of K+is difficult to achieve, because of initial seed reserves, and prolonged exudation in lupins can be maintained utilising only a small proportion of the K+originally present in the root tissue. Nevertheless, the data cast doubt on the general applicability of the concept that volume flow is maintained by an osmotic gradient with K+as the principal mineral ion

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06614.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Reed plants (Phragmites communisTrinius) were grown at NaCl concentrations up to 500 mMand their growth, mineral contents and leaf blade osmotic potential were determined. Addition of NaCl up to 300 mMdid not affect growth significantly. Sucrose, Cl‐and Na+concentrations in the shoots increased with the salinity of the medium and the shoot water content decreased. K+always contributed most to the leaf osmotic potential. Even in the presence of 250 mMNaCl in the rooting medium, the leaf blade contained only 50mMNa+, suggesting that the plants have an efficient mechanism for Na+exclusion.22Na+uptake experiments suggested that the retranslo‐cation of absorbed Na+from shoots to the rooting medium lowered the uptake of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06615.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The relationship between ethylene production, 1‐aminocyclopropane‐l‐carboxylic acid (ACC) concentration and aerenchyma formation (ethylene‐promoted cavitation of the cortex) was studied using nodal roots of maize (Zea maysL. cv. LG11) subjected to various O2treatments. Ethylene evolution was 7–8 fold faster in roots grown at 3 kPa O2than in those from aerated solution (21 kPa O2), and transferring roots from aerated solution to 3 kPa O2enhanced ethylene synthesis within less than 2 h. Ethylene production and ACC accumulation were closely correlated in different zones of hypoxic roots, regardless of whether O2was furnished to the roots through aerenchyma or external solution. Both ethylene production and ACC concentrations (fresh weight basis) were more than 10‐fold greater in the distal 0–10 mm than in the fully expanded zone of roots at 3 kPa O2. Aerenchyma formation occurred in the apical 20 mm of these roots.Roots transferred from air to anoxia accumulated less than 0. 1 nmol ACC (mg protein)‐1for the first 1.75 h; no ethylene was produced in this time. The subsequent rise in ACC levels shows that ACC can reach high concentrations even in the absence of O2, presumably due to a de‐repression of ACC synthase. The hypothesis was therefore tested that anoxia in the apical region of the root caused enhanced synthesis of ACC, which was transported to more mature regions (10–20 mm behind the apex), where ethylene could be produced and aerenchyma formation stimulated. Surprisingly, exposure of intact root tips to anoxia inhibited aerenchyma formation in the mature root axis. High osmotic pressures around the growing region or excision of apices had the same effect, demonstrating that a growing apex is required for high rates of aerenchyma formation in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06616.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Localization of two isoforms of glutamine synthetase (GS; EC 6.3.1.2) was investigated in different cell types, mesophyll cells and bundle sheath cells, of corn (Zea maysL. var. W64A × W182E) leaves by using ion exchange chrotnatography. In whole leaf extracts, relative activities of GS1 (cytosolic GS) and GS2 (chloroplastic GS) were almost equal. Purified mesophyll protoplasts and bundle sheath strands also showed similar proportions of GS1 and GS2. Methionine sulfoximine (1mM) enhanced the accumulation of ammonia when mesophyll protoplasts were incubated with nitrite or when bundle sheath strands were incubated with glycine. This clearly indicates a spatial separation of metabolism of NH+4derived from photorespiration and from reduction of NOJ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06617.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Tobacco (Nicotiana tabacumL. cv. Samsun) plants were treated once with 2,4‐dichlorophenoxyacetic acid (2,4‐D) at the 8‐leaf stage. The effect of the herbicide on leaf metabolism was followed over 7 days by determination of the ribonucleotide pools, including NAD+, NADP+and UDP‐sugars, by high‐preformance liquid chromatography. 2,4‐D treatment resulted in large changes in the nucleotide concentrations, the magnitude and sign of which were dependent upon the leafage. The nucleotide pools decreased in the apical tissue, but increased strongly in the mature leaves with the highest relative increase in the oldest leaf tested. The time course of the changes revealed a maximum on day 5 after 2,4‐D treatment. The increase in the adenine nucleotide pools, energy charge and the NADVNADP+ratio are interpreted to indicate a stress situation. The different responses of young, mature and senescent tissue to the synthetic auxin could reflect their different inherent sensitivity due to the natural a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06618.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Theoretical calculation of the germination response induced by repeated treatments, separated by a dark period long enough to enable fixation of the effect of the preceding treatment, is possible when defining the percentage germination induced by the first treatment as the responding proportion (p) of the total treated seed population. Consequently the germination response induced by a second treatment should be relative to the proportion (q) of the seed population not responding to the first treatment (q = 1 ‐ p).The fitting of these calculations with experimental data for the Very Low Fluence Response (VLFR) for germination of seeds ofKalanchoë blossfeldianaPoelln. cv. Vesuv, induced by repeated light pulses, suggests the independency of the effect of each treatment, i.e. the effect of the second treatment is neither positively nor negatively influenced by the first treatment.This hypothesis is not valid for calculation of the Low Fluence Response (LFR) for germination ofKalanchoëseeds induced by repeated light pulses, since the first light pulse does not result in a germination response. At least two irradiations are needed for an LFR while the third and following pulses increase the response much more than calculated with the proposed equation. It is suggested that the LFR inKalanchoë, in contrast to the VLFR, includes the involvement of some pre‐existing far‐red absorbing form of phytochrome (Pfr) and the involvement of dark reactions are to be considered.The effect of long irradiation times (up to 2xl05s) resulting in a (defined in this paper) high fluence response (HFR) for germination ofKalanchoëseeds is also discussed in terms of independently responding seed population

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06619.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effect of fruiting on carbon fixation and retention in leaves was monitored by measuring net photosynthesis (Pn) and total non‐structural carbohydrates (TNC) on a seasonal basis on mature fruiting and non‐fruiting sweet cherry trees (Prunus aviumL. cv. Bing). Pn was also measured diurnally during stages II and III of fruit development. Pn rates increased to between 18 and 20 mg CO2dm‐2h‐1during stage II of fruit development and were maintained until harvest. Diurnally, Pn increased in the morning to 20 mg CO2dm‐2h‐1and this rate continued until sunset. Leaf carbohydrate levels decreased in both fruiting and non‐fruiting trees beginning at the equivalent of stage II of fruit growth. Carbohydrates were lower in leaves and woody portions of current, 1‐ and 2‐year‐old shoots of fruiting trees. Although differences were found in levels of non‐structural carbohydrates, no differences in Pn were found in fruiting vs non‐fruiting plants on either a seasonal or a diurnal basis. Pn rates in swet cherry in the field were primarily affected by ontogeny and environment a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06620.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Terpenes were analyzed in needles of pollution injuredPicea abies(L.) Karst. of the Southern Black Forest (SW Germany) showing symptoms of montane yellowing. Compared to a set of healthy trees, a set of injured trees showed increased terpene hydrocarbon concentrations relative to needle fresh weight. This difference was even more pronounced when the terpene concentrations of green, healthy and yellowing, injured needles from the same internode of individual injured trees were compared. Increased terpene concentrations were observed in the basal parts of injured needles, while their distal parts exhibited a loss of terpenes. In addition, an alteration in the pattern of terpene occurrence was observable. Most striking was the changed ratio of α‐pinene toβ‐pinene. with marked increase of the latter, in injured needles. As indicated by ultratrace analysis of isolated mesophyll. vascular tissue and resin ducts of the needles, mono‐ and sesquiterpenes were found exclusively in resin ducts. The other tissues were virtually free of terpenes. Isolated resin from a single resin duct contained all terpenes (monoterpene hydrocarbons, alcohols and ketones, and sesquiterpene hydrocarbons) that are typical for the needle. An individual response to air pollution of each separate short resin duct in the needle may be

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06621.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A study of the kinetics of chlorophyll (Chl) synthesis in cotyledons of etiolated cucumber seedlings (Cucumis sativus L. cv. Delilah) treated with 5×10‐5M‐ben‐zyladenine (BA) showed that cytokinin, like a red light pulse, could inhibit as well as promote pigment accumulation depending on the length of the dark period following induction. Spraying intact, dark‐grown seedlings with BA, 24 h prior to white light exposure, eliminated the lag phase in Chl synthesis, while treatment with hormone 72 h before greening not only delayed the onset of synthesis, but it also reduced the amount of Chl accumulated after 24 h continuous white light. Impairment of Chl formation was correlated with inhibited regeneration of protochlorophyll and delayed appearance of the light harvesting Chlalbpolypeptide. Application of σ‐aminolevulinic acid (15 mM) 2hbefore white light exposure shortened the lag phase in Chl synthesis in control as well as in inhibited cotyledons, but the adverse effect of the red light and BA treatments on long‐term Chl accumulation (24 h) was not reversed. Application of glutamate did not stimulate Chl production. Simultaneous treatment with hormone and red light 72 h before greening enhanced their separate inhibitory effects on Chl synthesis, but when given together 24 h prior to white light, their promotive effects on pigment accumulation were

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06622.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Seeds of 4 annual cultivars of celery (Apium graveolensL. No. 15, 16, 17 and 143) were able to germinate in the dark, under high temperature, in relatively high concentrations of NaCl solutions and in the presence of relatively high concentrations of the inhibitors of the biosynthesis of gibberellin, paclobutrazol and ancymidol. Seeds of two biennial cultivars [Florida and Earlibell (EB)] showed very low germinability, or failed to germinate under the same conditions. These results are discussed in terms of endogenous gibberellin levels, which may be higher in the seeds of annual cultivars as compared to biennial ones.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1988.tb06623.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY