摘要:

In vitro shoots of cv. Doyenne ?Hiver pear (Pyrus communisL.) were irradiated under controlled environments for 6 h per day at 5 different levels of biologically effective UV‐B radiation (UV‐BBE). UV‐B exposure caused a progressive increase in apical necrosis above background levels and stimulated leaf abscission. Shoots grown for 2 weeks at 7. 8 mol m−2day−1of photosynthetic photon flux (PPF) and treated with 8. 4 or 12. 0 kJ m−2day−1UV‐BBEproduced up to 4 times more ethylene than those given 2. 2 or 5. 1 kJ m−2day−1UV‐BBEor untreated controls. Exposure of shoots to 12 kJ m−2day−1of UV‐BBEcaused an increase in free putreseine content after 4 to 14 days of irradiation. Shoots showed a decrease in CO2uptake after 3 days of UV‐B: thereafter, they appeared to recover their photosynthetic capacity. Under typical PPF conditions used in micropropagation (90 μmol m−2S−1). 8. 4 kJ m−2day−1of UV‐B radiation was injurious to realatively tender tissues of in vitro pear shoots: increasing the level of UV‐BBEto 12 kJ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The temperature dependence of the activity of ion channels was investigated, by means of the patch‐clamp technique in the ‘whole‐cell’ configuration, using protoplasts and vacuoles isolated formArabidopsis thalianaL. cultured cells. The effect of temperature changes in the range 11–22°C was tested on the hyperpolarization and depolarization‐activated K+currents in the plasma membrane and on the hyperpolarization‐activated K−currents in the tonoplast (vacuolar membrane). All 3 kinds of currents were unaffected by increasing temperature up to 15°C and were activated be

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We examined the effects o long‐term hypoxic growth conditions on net uptake and transport of P to shoots of pond Pine (Pinus serotina Michx.), a moderately flood‐tolerant southern pine. Seedlings were grown under aerobic orhypoxic solution conditions for 4–5 weeks in continuously flowing solution culture containing 100 μMP. Short – and long‐term32P. experiments were then concluded with intact seedlings to determine rates of32P influx, efflux and net transport to the shoot. Shoot fresh weight/root fresh weight ratios were significantly higher under hypoxic gorwth conditions, reflecting the larger reduction in root growth than shoot growth, despite extensive aerechyma formation in roots. Estimates for the unidirectional influx of32P in aerobic and hypoxic seedlings were 1.43 and 3.20 μmol P (gFWroot)−1h−1, respectively. However,32P accumulation between the two treatments became similar within 8 h, suggesting that efflux was also higer in seedlings from the hypoxic treatment. Indeed in a separate experiment, hypoxic growth conditions increased efflux by over 60%. Transport of32P to shoots was significantly reduced under hypoxic growth conditions, despite higher root P concentrations and lower shoot P concentrations. After 48 h,32P accumulation in roots was similar between the two treatments. Yet total accumulation of seedling32P decrcased by 31% under the hypoxic treatment, largely because of reduced transport of32p to the shoot. The lower accumulation of32by shoots of seedlings in the hypoxic treatment may be the result of a direct inhibition on the transport process in O2‐defident tissues, but could also reflect a slower turnover or labeling of the ool available for transport. Indeed, the percentage of total32P in. roots present in the soluble P. (or transportable form of P) was about 33% lower in seedlings from the hypoxic treatment, probably reflecting increased assimilation into organic compounds as well as chelation with iron. Our results suggest that P transport to the shoots of acclimated seedlings may be more sensitive to hypoxic solution conditions than influx at the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Potato tubers (Solanum tubersumL. cv. Grata) were stored for atleast 1 week at room temperature and then incubated with an equal amount of apples (Malus domesticaL.) for 2 days. After this treatment, intact tuber mitochondria isolated by Percoll gradient centrifugation showed a high degree of induction of the alternative oxidase, measured as cyanide‐resistant, salicylhydroxamic acid‐sensitive respiration. With succinate as substrate an activity of more than 130 nmol O2(mg protein)1mintwas obtained. An assay of the alternative oxidase using duroquinol as an electron donor was developed. To become reliable the assay required the presence of defatted bovine serum albumin (BSA) and catalase (EC 1. 11. 1. 6). Furthermore, a lowering of the assay temperature to 15°C improved the stability of the duroquinol‐based activity. One remarkable finding was that with duroquinol (or external NADH) as substrate the alternative oxidase was synergistically activated by succinate (as well as by malate) even in the presence of the succinate dehydrogenase inhibitor malonate. Our interpretation is that succinate and malate (indirectly) activate the alternative oxidase and that this activation is part of a physiological mechanism for regulation of the alternative o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Auxin‐induced elongation of epicotyl segments of azuki bean (Vigna angularisOhwi et Ohashi cv. Takara) was suppressed by a fucose‐binding lectin fromTetragonolobus purpureasMoench and by polyclonal antibodies raised against xyloglucan heptasaccharide (Xyl3Glc4) when the cuticle present in the outer surface of epicotyls was abraded. In contrast, elongation of non‐abraded segments was not influenced by the lectin or the antibodies. Epicotyl segments, from which the epidermal and the outer cortical cells had been removed, elongated rapidly for 2 h and than only slowly. Auxin slightly stimulated elongation of the inner tissue segments in the phase of slow growth. Neither in the presence nor in the absence of auxin did the lectin or the antibodies affect elongation of the inner tissue segments. The split portions of outer surface‐abraded epicotyl segments incubated in buffer extended outward, and auxininhibited this outward bending. The lectin and the antibodies reversed the effect of auxin on bending. The fucose‐binding lectin pretreated with fucose or the immunoglobulin fraction obtained from preimmune serum exhibited little or no inhibitory effect on auxin‐induced elongation of abraded or split segments. These results support the view that a breakdown of xyloglucans in the epidermal cell walls plays an essential role in auxin‐induced elongation in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Seed cones were collected from open‐pollinated trees of Norway spruce (Picea abies) in a seed orchard from pollination until maturation of the seeds. Immature embryos were isolated for embryogenic tissue cultures that were maintained either on solidified medium or as liquid cultures. By transferring young somatic embryos to medium containing 90 mMsucrose and 7. 6 μMABA growth continued to mature embryos that accumulated storage reserves in both the hypocotyl‐shoot axis and the cotyledons. Both zygotic and somatic embryos at different developmental stages were processed for microscopy as were the megagametophytes. Total protein was extracted from the seed material at intervals during development and analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. These analyses revealed that storage protein started to accumulate in the megagametophytes at the time when embryos were growing into the gametophytic tissue, while it occurred a few weeks later in the embryos at rapid embryo growth and organ differentiation. Lipid bodies also became abundant in the mature plant material. Although plastids with prominent starch grains were very frequent in both megagametophytes and embryos during development they were not observed in the desiccated tissues. Zygotic and somatic embryos displayed a similar developmental pattern.By sequential salt‐extraction and dilution two fractions highly enriched in storage protein were obtained. One fraction (G‐1), requiring higher salt concentration for protein solubilization, was dominated by a protein migrating to around M, 55000–60000 when separated under non‐reduced condition. After exposure to reducing agent this protein was replaced by two new ones with M, 33000 and 22000 giving evidence of disulfide bonded polypeptides. The other fraction (G‐2), was dominated by polypeptides around M, 42000 and low molecular mass polyp

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Changes in cytokinin (zeatin – Z, zeatin riboside – ZR, isopentenyladenine – iP, isopentenyladenosine – iPA) levels were determined under light regimes inductive and non‐inductive for flowering in leaves, stems, roots and apical parts of short‐dayChenopodium rubrumand long‐dayChenopodium murale.In leaves. stems and roots of both plant species the level of cytokinins (inC. rubrumof Z and ZR, inC. muraleof Z. ZR, iP and iPA) decreased by about 50% during the dark period and increased again during the subsequent light period, No significant changes in cytokinin levels were observed in continuous light. In apical parts ofC. rubrumcytokinin level (Z, ZR, iP) was dramatically increased (by 400–500%) at the end of the dark period and decreased to about the original value during the following light period, while no changes were observed in continuous light. In apical parts ofC. muralethe level of cytokinins doubled during floral induction consisting of 10 days of continuous light. A red (R) break (15 min at the 6th h of darkness), which prevents flowering inC. rubrum, has no significant effect on cytokinin levels in leaves at the end of darkness. Cytokinin levels increased 1 h after R and decreased again rapidly. On the other hand, the increase of cytokinin level in the apical parts ofC. rubrumwas largely prevented by the R break. These effects of R on cytokinin levels were not reverted by far‐red (FR), while the effect on flowering was reverted. It may be concluded that there is no correlation between changes in cytokinin levels in leaves. Stems and roots and photoperiodic flower induction, as both species, representing different photoperiodic types, showed similar changes under the same light regime. The increase of cytokinin levels in apical parts of both photoperiodic species during floral induction suggests a role (increased cell division and branching) for cytokinins

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Cellular changes in thin cell layer (TCL) explants of stem origin ofBrassica napusL. cv. Vega were studied from 0 to 15 day by light and transmission electron microscopy. Apical and basal ends of the old explants were analysed separately. Quantitative and qualitative analyses showed that during the first culture day the parenchyma cells enlarged significantly as did the cytoplasm/vacuole ratio. The cytoplasm contained increased rough endoplasmic reticulum (RER), polysomes and dictyosomes associated with both coated and uncoated vesicles. The cell enlargement continued during the first 5 days of culture. The structural organization of the cell wall became somewhat loose and inhomogeneous. Parenchyma in the basal end divided frequently, resulting in several centres of division, while cell division in apical cells was less frequent and cells there remained enlarged. Starch accumulation started on the first day and increased until the third day. i. e. until cell divisions became more frequent. The starch content of dividing cells gradually decreased and starch was almost totally lacking in 15‐day‐old explants. Starch grains remained numerous, however, in the large non‐dividing apical cells, except in those cells adjacent to the medium. Cell divisions started close to medium in explants containing vascular tissue, but closer to the epidermis in the explants without vascular tissue.The results show how rapid (one day) striking changes in the cells take place and suggest that optimal hormone concentration and intertissue relations between epidermis and parenchyma and between parenchyma and vascular tissues as well as intercellular relations among parenchyma cells determine the first cell division sites and planes in the explants. Although the cells change from elongated to spheroid, their original polarity remains as evidenced by the formation of more numerous basal shoot primordia than in apical shoot prim

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Leaves and bulbs of garlic (Allium sativumL.) contain a chitinase which can be separated into three different isoforms with similar molecular structure and N‐ terminal amino acid sequence. SDS‐PAGE of the alkylated chitinase revealed two distinct polypeptides of 32 and 33 kDa. Induction studies of the chitinase in leaves of garlic plants indicated that not only treatment with ethephon or salicylate and wounding but also a temperature shock strongly increased the enzyme level.cDNA libraries constructed from poly(A)‐rich RNA isolated from young garlic shoots and bulbs were screened for chitinase clones using the cDNA clone CCH4 encoding a basic potato chitinase as a probe. Two different cDNA clones (designated CHITAS 1 and CHITAS 2)of ca 1 000 bp were isolated and their sequences analyzed. The amino acid sequences deduced from both cDNA clones were homologous though not identical to the N‐terminal sequences of the mature chitinases. Although both clones encode highly homologous chitinases their sequences definitely differ in that they have different signal peptides and one of them contains a glycine‐rich domain. The garlic chitinases are apparently translated from an mRNA of 1200 nucleotides which encodes a proprotein of approximately 32 or 33 kDa for CHITAS 1 and CHITAS 2, respectively. Co‐translational removal of the signal peptide will result in a 30 (for CHITAS 1) or 31 kDa (for CHITAS 2) protein with an isoelectric point of 4. 94 (for CHITAS 1) or 6. 12 (for CHITAS 2). Garlic chitinases are encoded by a small gene family as shown by Southern blot analysis of genomic DNA isolated from garlic.The garlic chitinases show a high degree of sequence homology to the previously isolated chitinases from dicotyledonous as well as monocotyledonous species, indicating that these proteins have been conserved from an evolutionary po

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Leaf discs from spinach were exposed to a photon flux density of 1250 μmol m−2s−1at 5°C for 2 or 3 h in ambient air. Photoinhibition of photosystem II (PS II) was measured by means of chlorophyll fluorescence. Recovery of photosystem II was followed at 6°C and 20°C in low light or darkness for periods up to 12 h.The experimental setup allowed kinetic resolution of different phases of recovery. The experiments revealed a temperature dependent dark recovery phase and two distinct light‐ and temperature dependent phases: (1) A relatively fast, light dependent recovery phase occurred in parallel with partial recovery of basic fluorescence at 6°C and 20°C. A population of PS II centers with very slow fluorescence induction kinetics, which had accumulated during photoinhibition treatment, disappeared during this phase. This fast recovery phase is proposed to represent reactivation of photoinhibited PS II, without dissassembly or incorporation of new D1‐protein. (2) A relatively slow light‐dependent recovery phase took place at 20°C, but not at 6°C. In the presence of the chloroplast translation inhibitor streptomycin, part of the 2nd phase was inhibited. This phase is proposed to involve assembly of new Photosystem II centers, which is partly dependent on de novo synthesis of D1‐reaction center protein, but presumably is also using a preexisting pool of D1‐protein. Cold acclimation of the leaves resulted in a decreased sensitivity for photoinhibition of photosystem II. Recovery of photoinhibited photosystem II at 6°C of the cold‐acclimated leaves was faster than in non‐acclimated leaves, but this effect can be ascribed to diminis

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY