摘要:

The effects of UV‐C (254 nm) and UV‐B (280‐320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves ofHibiscus rosa‐sinensisL. were investigated. UL from leaves exposed to UV‐B and UV‐C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light with time was detected. UV radiation increased peroxidase activity, which also reached a maximum 72 h after irradiation. UV‐B and UV‐C both reduced variable chlorophyll fluorescence. No effect on the amount of chlorophyll or UV screening pigments was observed with the short‐term irradiation used in t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05463.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Hemerocallisplantlets maintained in vitro for extended periods of time in tightly closed culture vessels frequently show a phenotype, albeit on a miniaturized scale, typical of more mature, field‐grown plants. The positive relationship of elevated ethylene in the headspace of such vessels to the phase shift from juvenile to mature form is established. Rigorous restriction in air exchange with the external environment by means of silicone grease seals hastens the phase change and improves uniformity of response. Although some plantlets may take longer to accumulate enough ethylene in sealed jars to undergo change, added ethylene and ethylene‐releasing agents promote it. Ethylene adsorbants (e.g. mercuric perchlorate) block the shift of juvenile to mature form. Critical ambient ethylene level for the shift is ca 1 μl l−1. Levels up to 1000 μl l−1do not hasten the response but are not toxic. The phase change is fully reversible when air exchange permits ethylene to drop below 1 μl l−1. At least 1 μl l−1ethylene is required to sustain the mature phenotype. The ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG) prevents the phase change, while the ethylene biosynthesis intermediate 1‐aminocyclopropanecarboxylic acid (ACC) improves it. KOH, as a CO2absorbant, does not prevent the phase change. Histology sections demonstrate subtle changes in the form of shoot tips of plantlets underg

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05464.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

It is demonstrated that chlorophyllbdoes not only derive from chlorophylla, but is also formed separately from an in vivo‐occurring chlorophyllideb. The branching point for the latter synthesis is at the level of chlorophyllide, since no protochlorophyllidebwas detectable. We have indications that the enzyme oxidizing chlorophyllato chlorophyllbaccepts also non‐phytylated 17,18 dihydroporphyrins and is not restricted to chlorophylls. Preparations of chlorophyllideaand chlorophyllacould both be transferred with the same enzyme fraction to chlorophyllideband chlorophyllb, respectively. Preliminary experiments show this enzyme to be membrane bound and light independent. An updated scheme for chlorophyllbbiosynthesis is presen

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05465.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The development of chilling injury symptoms in zucchini squash (Cucurbita pepoL. cv. Ambassador) was reduced by preconditioning the fruit for 2 days at 10°C. In the control group, held continuously at 2.5°C, increasing chilling injury correlated with an increase in putrescine and decreases in spermidine and spermine. Preconditioning led to a significant increase in spermidine arid spermine levels, beginning after the initiation of storage at 2.5°C and lasting for 5 days, after which the levels decreased but remained elevated relative to the control. The elevation of polyamine levels by direct treatment of the fruit with spermine prior to storage resulted in reduced chilling injury, indicating that polyamines may be involved in the protective mechanism of preconditioning. We have also examined the extent of lipid peroxidation by determining the levels of chloroform‐soluble fluorescent products in the skin of the fruit subjected to chilling. The chilling injury in the control group resulted in an increase in the fluorescent products. The levels of fluorescent products were significantly reduced by the preconditioning treatment. These results may indicate that polyamines can act to prevent chilling injury in squash by a mechanism which involves protecting membrane lipids from peroxida

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05466.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The light microenvironment within leaves ofMedicago sativaL. cv. Armor was related to the anatomy of the epidermis. Leaf epidermal cells had a convex shape and appeared to act as lenses that focussed light within the upper region of the palisade. In leaves irradiated with collimated light, epidermal focussing was demonstrated by ray tracing, photomicrography and fiber optic probe measurements, where lens signatures were observed. No relationship was observed between the location of focal spots within the palisade and chloroplast positioning. Epidermal focussing could be largely eliminated by irradiating leaves with diffuse light or by coating their surface with a thin layer of mineral oil that closely matched the refractive index of the cell walls. Measurement of variable chlorophyll fluorescence after elimination of epidermal focussing on the adaxial leaf surface caused a 19 and 11% decrease in the initial fluorescence level (F0) and maximum fluorescence (Fmax), respectively, whereas similar measurements from the abaxial surface were twice as large. These results suggest that some of the chloroplasts within the leaf may be adapted to local high‐light conditions created by the epidermi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05467.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Two phases of bud activity were identified in the new growth of one‐year‐old erect coppice shoots on 11‐year‐old low‐pruned stumps of mulberry (Morus albaL. cv. Shin‐ichinose) in spring, the sprouting phase in which the majority of the buds, including the basal ones, sprout and elongate, and the dominance phase (starting 4–5 weeks after sprouting) during which the upper laterals begin to assert dominance and suppress the growth of lower laterals, becoming new leading shoots. In contrast, arching before sprouting markedly inhibited buds on the under side, leading to poor shoots. By late April, the sprouts on the upper side grew readily into new erect shoots, resulting in considerable dominance over those from the lateral sides. Of these erect shoots, those located closer to the stem base grew more in May and June. The effects of arching made during the sprouting phase (late April) on bud activity and shoot lengths were generally similar to those of earlier archings before spring bud bursting. Separation of the shoots from the upper and under sides by longitudinal, horizontal splitting of the arched stems in late April did not affect the inhibited elongation of the shoots from the under side. These results suggest that in the response to arching before and in late April, the effects are related to spring bud bursting and gravimorphism. In contrast, arching during and after the dominance phase (May) had no gravimorphic effects on growth of the shoots on the upper side, although there was a stimulation of outbreak of the buds on the upper side, which remained dormant during spring bud bursting.Continuous basal applications of abscisic acid in aqueous solution inhibited bud break and shoot growth of the postdormant erect stem segments, and defoliation of the new shoots markedly. In contrast, similar applications of an ethylene‐releasing compound, Ethephon, depressed shoot elongation slightly, but enhanced defoliation greatly. Gibberellic acid (GA3) stimulated shoot elongation, but depressed l

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05468.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Indole‐3‐acetic acid (IAA) was purified by high performance liquid chromatography (HPLC) and identified by gas chromatography ‐ mass spectrometry (GC‐MS) in leaf extracts ofBegonia × cheimanthaEverett cv. Nova. The content of IAA and of gibberellins A4, A9, A19 and A20 (GAs) previously identified in this material, were quantified by GC‐MS in leaves ofBegoniaplants grown under different temperature and daylength conditions, using deuterated compounds as internal standards. GA1, which was also identified, was present in too low quantities for reliable quantitation. Rapid and significant decreases (within 2–4 days) occurred in the content of both IAA and GAs when the plants were transferred from conditions which are non‐inductive for adventitious bud formation and flowering (24°C/long day) to inductive conditions (24°C/short day, 15°C/long day or 15°C/short day). GA4 and GA9 were affected by photoperiod only, whereas IAA, GA19 and GA20 were affected by both photoperiod and temperature. The data suggest that biosynthesis of GA9 and GA4 are blocked in short days at a step located before GA9. Conversion of GA19 to GA20 seemed to be blocked by both short days and low temperature, while an additional block located before GA19 seemed to be imposed in 15°C/short day. The results confirm earlier results and support the hypothesis that photoperiod and temperature effects inBegoniaare mediated by

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05469.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Dicarboxylic acid transport mutants ofRhizobiumspecies are usually deficient in their ability to fix atmospheric dinitrogen. We report here a study comparing the physiology of root nodules onPhaseolus vulgarisL. cv. Goldie induced by an effective strain ofRhizobium leguminosarumbiovarphaseoliand a C4‐dicarboxylic acid utilization mutant. The mutant, while able to form nodules, was ineffective in N2fixation. Carbohydrates and organic acids of roots and nodules formed by the 2 strains were monitored at 3‐day intervals from 13 to 34 days after inoculation. Both carbohydrates and organic acids accumulated in ineffective nodules in comparison with the effective nodules. The concentration of malic acid was tenfold higher in ineffective nodules than in effective nodules. Other organic acids, i.e., lactate, malonate, ascorbate and gluconate, were also detected. Lactate and ascorbate were the only other organic acids accumulating in ineffective nodules. The most prevalent carbohydrates found in both types of nodules were sucrose, glucose and fructose. Myo‐inositol was the only cyclitol detected in both types of nodules. Carbohydrates and organic acids were present in lower concentration in roots than in nodules, except for lactate. These compounds were not consistently detected in higher concentration in roots from plants inoculated with the mutant strain, as was the case in no

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05470.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Exo‐polygalacturonase (exo‐PGase, EC 3.2.1.67) activity has been detected in a culture filtrate of cell suspension cultures of carrot (Daucus carotaL. cv. Kintoki). The extracellular exo‐PGase was purified to electrophoretic homogeneity using DEAE‐Sephadex A‐50 ion‐exchange chromatography, Sephadex G‐150 gel filtration, and preparative polyacrylamide gel electrophoresis (PAGE). The molecular mass of the purified enzyme was calculated to be 48 kDa from Sephadex G‐200 gel filtration, and 50 kDa from sodium dodecyl sulfate (SDS)‐PAGE after treatment with SDS and 2‐mercaptoethanol. The isoelectric point was at pH 6.2. The Kmand Vmaxvalues for polygalacturonate (degree of polymerization: 52) were 14.4 μMand 25.6 μmol (mg protein)−1h−1, respectively. The optimal activity in McIlvaine's buffer occurred at pH 4.6. The enzyme activity was inhibited by Ba2+, Cu2+, Mn2+and Hg2+. The enzyme was involved in ca 15% hydrolysis of the acidic polymer purified from carrot pectic polysaccharides, and connected with the release of galacturonic acid. Even after an exhaustive reaction the enzyme had, however, little or no effect on cell walls

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05471.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The metabolism of14C‐putrescine and the changes in the endogenous concentrations of putrescine, spermidine and spermine were studied when cotyledons ofPinus radiataD. Don were cultured under shoot‐forming (SF, + N6‐benzyladenine) and non‐shoot‐forming (NSF, ‐ N6‐benzyladenine) conditions. Differences in the total uptake of14C‐putrescine during a 2 h pulse feeding were not significant between the SF and NSF cotyledons except on day 3. The maximum uptake of label was on day 3 in the SF cotyledons, which released the highest amount of14CO2as well.14C from the labeled putrescine was incorporated mainly into γ‐aminobutyric acid, aspartate and glutamate. High performance liquid chromatography of the endogenous polyamines indicated that spermidine was the most predominant polyamine in the cultured cotyledons of radiata pine. Spermine increased by about 60% in the SF and 25% in the NSF cotyledons between days

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05472.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY