摘要:

Chlamydomonas reinhardtiiDangerad 11–32(90) (−), which exhibits C3 properties, andAnacystis nidulans(Strain no. UTEX 625), which exhibits C4 properties, were used to study the effects of triacontanol on growth, photosynthesis and photorespiration. Photosynthetic rate was measured as CO2 uptake and the O2 inhibition of photosynthesis was used as a measure of photorespiration. Triacontanol dissolved in chloroform and dispersed in Tween‐20 and triacontanol colloidally dispersed in an aqueous solution of sodium tallow alkyl sulfate were tested.Chlamydomonascultures increased significantly in cell number after 4 days, and in chlorophyll content after 3 days of treatment with 2.3 × 10−8M TRIA in chloroform/Tween‐20. In cultures ofAnacystisthe chlorophyll content became significantly higher 3 days after treatment with 2.3 × 10−9M TRIA and the cell number was noticeably higher than the controls.CO2uptake by triacontanol‐treatedChlamydomonascultures was about the same in both 2 and 21% O2, and the O2 inhibition was significantly reduced as compared with the controls. Photosynthesis inAnacystiswas O2‐insensitive under the experimental condition used. WhenAnacystiswas treated with triacontanol there was no change in the rate of CO2 uptake and no change in the O2 sensitivity of its CO2 uptake. It appears that triacontanol affects some process which regulated the balance between photosynthesis and photorespiration, but other processes which result in increased growth are proba

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05726.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Variants resistant to antimetabolites are useful for investigating metabolic regulation and biochemical genetics in organisms. In this study, suspensions of mutagenized sugarcane (Saccharumsp.) cells, originating from a stalk parenchyma explain of the Hawaiian variety 50–7209, were used to investigate the feasibility of isolating variants resistant tol‐canavanine, glyphosate [N‐(phosphonomethyl)glycine], ophiobolin A and orthovanadate. Rigorous retesting of clones which grew on selection media led to the identification of three cell lines, two of which were resistant to glyphosate and one to orthovanadate. No variants were isolated which showed a persistent resistance either tol‐canavanine or ophiobolin A.The results demonstrate that resistant variants do occur, or can be induced, in sugarcane cell suspensions and that they can be rescued and cul

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05727.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

An investigation of the roles of calcium and magnesium ions in symbiotic nitrogen fixation by legumes has shown that alfalfa plants (Medicago sativaL. cv. Saranac and Apollo) deficient in either cation were poorly nodulated and retarded in growth on nitrogen‐free media. This effect was reversed by supplementation with normal levels of these cations. After recovery, the calcium deficient seedlings showed continuing effects of early mineral deficiencies but recovered to 75% of the nitrogenase activity and had nearly the same yield as control plants. Magnesium deficient plants recovered nitrogenase activity to the same degree but grew to only about 50% of the weight of controls. Supplementation of non‐deficient seedlings grown on N‐free media with varying amounts of Ca2+and Mg2+resulted in the identification of an optimal ratio of calcium and magnesium near 2 when neither cation was growth limiting. A highly significant positive correlation was obtained between yield of dry matter and the fraction of total expressed nitrogenase activity that was actually available for dinitrogen reduction (nitrogen reducing equivalent). Bacteroids isolated from root nodules and freed of plant cytoplasmic components required high magnesium levels for maximal utilization of externally supplied ATP and dithionite. Ca+was antagonistic to this activity but complemented Mg2+in stimulating the respiration‐supported nitrogenase activity of intact bacteroids which had been treated with a chelating agent. The effects of calcium and magnesium on the nitrogenase system of intact bacteroids may be due to binding of the Ca2+ions to the bacteroid m

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05728.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Auxin (IAA, 5 × 10−5M) partially prevents the increase in the rate of phosphate uptake during ageing of potato tuber discs (Solatium tuberosumL. cv. Bintje), whereas fusicoccin (FC, 10−5M) stimulates it. After the development of enhanced phosphate transport capacity, the response to fusicoccin is greater than with fresh discs. Complementary experiments on K+(86Rb) absorption show that FC also slightly enhances the rate of K+uptake, while IAA has no much effect. It is suggested that IAA acts specifically on the development of a mechanism which occurs during the ageing period, while FC action may be more directly linked to the system of phosphate transport it

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05729.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

An electronic flash unit is used to deliver, at the beginning of a 10 min dark period and within a few ms, large doses of light toAlbizzia julibrissinpinnules, to ascertain their effects on the rate of pinnule closing. In a series of alternating light flashes at 710 and 550 nm, the first 710 nm light flash significantly retards closing. A following light flash at 550 nm negates the far‐red induced delay. The second 710 nm light flash delays closing less effectively than the first when given within 4 s after the green flash, but is just as effective when given after 30 s. The delay brought about by the second 710 nm light flash is again abolished by a light flash at 550 nm. A light flash at 660 nm has no effect on pinnule closing by itself and is also ineffective in reversing the far‐red induced delay. A series of ten 710 nm light flashes becomes most effective in delaying closure when there is a dark interval of one min between flashes. The closing delay induced by a 710 nm light flash escapes reversal by a 550 nm light flash when the dark interval between the two flashes exceeds 2–3 min. A 750 nm light flash has no retarding effect on pinnule closing, but it becomes effective when preceded by a 660 nm or 550 nm light flash. The results obtained are suggested to be due to light absorbed by phytochrome and an unknown photoreceptor with green, far‐red photoreversal p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05730.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Activity of RNase was studied in attached and detached leaves of 7‐day‐old ragi (Eleusine coracanaGaertn. cv PR 202) plants during senescence using crude enzyme extracts. The RNase activity was relatively constant in attached leaves. In excised leaves incubated in the dark there was a rapid rise in enzyme activity up to 48 h, followed by a decline. No such decrease was observed in the light. Benzimidazole and gibberellic acid suppressed the activity of RNase up to 48 h in the dark and 96 h in the light. Both the growth regulators also prevented the post‐48 h decline in RNase activity of dark incubated excised leaves. Decline in the levels of chlorophyll and RNA in the illuminated excised leaves was not affected by 3‐(3,4‐dichlorophenyl)‐1,1‐dimethyIurea, but the inhibitor prevented the photo‐induced rise in RNase activity. Cycloheximide and actinomycin D could completely prevent both detachment (increase in enzyme activity after the leaf is excised) and photo‐induced rise in RNase activity. Benzimidazole and gibberellic acid prevented the rise in the activity of RNase on one hand and maintained it on the other by their influence on its biosynthesis. Photoinduction of RNase and photo‐induced retardation of senescence are concluded to be two

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05731.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Hypobaric conditions and treatments with ethylene and the ethylene analogue propylene were used to investigate effects of oxygen and elhylene on 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content, ACC synthase activity and ethylene production of apples (Malus sylveslrisMill. cv. Golden Delicious). Prcclimacteric apples were stored in air at 6.6 kPa (reduced pressure); 6.6 kPa ventilated with pure O2; 6.6 kPa ventilated with 2600 μl 1−1C2H4; and in air at 101.3 kPa (atmospheric pressure) for 4 months at 4°C. No ACC synthase activity was detectable in apples stored at 6.6 kPa, whereas ACC synthase activity was induced in apples stored at 6.6 kPa and ventilated with either O2or C2H4. In a further experiment, preclimacteric apples were stored for 14 days either in air at 20 kPa or at 20 kPa ventilated with pure O2. Both treatments were supplied with 58 500 μl 1−1propylene from day 0 to day 9 or from day 9 to day 12. Ethylene production of apples treated with propylene from day 0 to day 9 increased earlier than ethylene production of untreated apples. Propylene treatment from day 9 to day 12 did not stimulate ethylene production. Ethylene and propylene induced and stimulated extractable ACC synthase activity and ACC formation of apples. Oxygen enhanced this effect. The results also suggest inhibition of in vivo ACC synthase activity

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05732.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Dimethylsulfoxide (DMSO) acts on dark‐ and light‐induced movements exhibited by leaflets of isolated leaves ofCassia fasciculateMichx. The closing movement (scotonasty), induced when the leaves are placed in darkness during the normal period of daylight, was inhibited, whereas the opening movement (photonasty), when the leaves arc transferred to light during the normal period of darkness, was promoted. The concentration for significant effects of DMSO was 1% (v/v) when applied over a 3‐h period. After five days, a necrosis of the leaflets was observed for DMSO concentrations as small as 0.1%, applied over a 6‐h period. Complete abscission took place if 3% DMSO was applied for more than

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05733.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Characteristics of membrane‐associated ATPase from commercial Hawaiian varieties of sugarcane (Saccharumspp. hybrids) were investigated in preparations from sugarcane cell suspension culture and from stalk tissues of the intact plant. In order to examine comparable preparations, protoplasts and vacuoles, in turn, were obtained from both sources. ATPase from preparations of crude protoplast membranes and tonoplast had a pH optimum of 6 to 6.5. The relative effectiveness of divalent cations in stimulating ATPase was Mg2+>Mn2+≥ Co2+>Ca2+≥ Zn2+. Enzyme activity was not stimulated by K+, nor by other monovalent cations. Protoplasts and vacuoles from both sources showed significant acid phosphatase activity. Acid phosphatase activity was inhibited by molybdate, but ATPase activity was unaffected. Membrane preparations from protoplasts contained inorganic pyrophosphatase, but enzyme activity was low or not present in tonoplast preparations. Cell suspension and stalk tissue preparations hydrolyzed a large number of nucleoside di‐ and triphosphates. The hydrolysis is most likely due to a series of enzymes rather than a single enzyme. ATPase from protoplast and tonoplast preparations was inhibited 30–50% by diethylstilbestrol and sodium ortho‐vanadate and was unaffected by ionophores. This study illustrates the complexity of phosphohydrolase activities in membrane preparations from sugarcane. The study, however, also illustrates substantial similarity in the behavior of these enzymes, whether they are derived from the plant itself or from cell cultures originating from comparable tissues o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05734.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Using excised roots ofAtriplex hortensisL., cv. Gelbe Gartenmelde, the uptake, accumulation and xylem transport of K+and Na+have been measured. Influx as well as xylem transport proved to discriminate little between K+and Na+, when considered in relation to the external solution. Both K+and Na+inhibited the uptake and xylem transport of each other to about the same degree. Measurements of intracel‐lular Na+fluxes by means of compartment analysis indicated that the low degree of K/Na discrimination during uptake was due to low influx selectivity. Moreover, K+/Na+exchange at the plasmalemma was not very efficient in Atriplex roots. In order to establish the basis of the low K/Na discrimination in xylem transport, the rates of K+and Na+transport were related to the cytoplasmic K+and Na+concentrations to yield the selectivity ratio of transport, S(transport) = (ϕcx(K) × [Na+]c)/(ϕcx(Na) × [K+]c). Under all conditions this ratio was far below one indicating that Na+was favoured during xylem release in excised roots ofAtriplexat low external concentrations. The implications of this discrimination in favour of Na+ are discussed with respect to salt tolerance of A.hort

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb05735.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY