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31.
Comparison of phosphorus mobilization during monocarpic senescence in rice cultivars with sequential and non-sequential leaf senescence 总被引:1,自引:0,他引:1
The senescence pattern of the three uppermost leaves of four rice (Oryza sativa L.) cultivars viz. Ratna, Jaya, Masuri and Kalojira was analysed in terms of decline of chlorophyll and by measuring [32P]-phosphate retention and export from leaf to grains during the reproductive development. With the advancement of reproductive development, the cultivars Masuri and Kalojira showed a sequential mode of senescence, but the cultivars Ratna and Jaya showed a non-sequential mode of leaf senescence where the flag leaf senesced earlier than the older second leaf. Foliar spraying with benzyladenine (0.5 mM) significantly delayed, and abscisic acid (0.1 mM) accelerated, leaf senescence. In untreated control plants, the second leaf had the highest export of labelled phosphate among the leaves at the grain formation stage (0–7 days) in Masuri and Kalojira. This was compensated by the flag leaf at the grain development stage (7–14 days), whereas export of [32P]-phosphate was highest from the flag leaf of Ratna and Jaya at the grain development stage. Compared with the control, benzyladenine treatment caused higher retention of [32P]-phosphate in the leaves and also export to the grains, but abscisic acid treatment gave lower retention and export of [32P]-phosphate to the grains. The amount of [32P]-phosphate export from a mother to a daughter shoot developed in the axil of the second leaf of plants with the panicle removed, was less than that to panicles remaining on control plants of all cultivars. When the panicle had been excised, the greatest export of [32P]-phosphate took place from the second leaf to the daughter shoot in all cultivars. Excision of the panicle delayed leaf senescence as compared with intact controls and maintained an age-related leaf senescence pattern in all the four cultivars. The results presented here demonstrate that mobilization of phosphorus from leaf to grains, regardless of cultivar or age and position of the leaf, correlates well with the senescence of that leaf. 相似文献
32.
33.
H. J. Weigel 《Physiologia plantarum》1985,63(2):192-200
Photosynthetic CO2-fixation of mesophyll protoplasts of lambs lettuce [Valerianella locusta (L.) Betcke] was inhibited by short time exposure to Cd+. Inhibition was due to uptake of the metal ion into the protoplasts and increased with increasing Cd2+ concentrations and the time of preincubation. A 10 min pretreatment at 2 mM Cd2+ reduced CO2-fixation by 40–60%. Inhibition of photosynthesis was independent of the light intensity to which the protoplasts were exposed. Measurement of the lightinduced electrochromic pigment absorption change at 518nm and chlorophyll fluorescence studies revealed that primary photochemical reactions associated with the thylakoid membranes were not affected by the metal ion. Also, light activation of the ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) was not inhibited by Cd2+. Under rate-limiting CO2 concentrations, inhibition of CO2-fixation was smaller than at Vmax of CO2 reduction indicating that the carboxylation reaction of the Calvin cycle is not susceptible to Cd2+. Cd2+ treatment of protoplasts significantly extended the lagphase of CO2-supported O2-evolution and partly inhibited light activation of the glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) and the ribulose-5-phosphate kinase (EC 2.7.1.19). Measurement of relative concentrations of [14C]-labeled Calvin cycle intermediates showed that Cd2+ caused a decrease in the 3-phosphoglycerate/triose phosphate ratio and an increase in the triose phosphate/ribulose-1,5-bisphosphate ratio. It is concluded that in protoplasts Cd2+ affects photosynthesis mainly at the level of dark reactions and that the site of inhibition may be localized in the regenerative phase of the Calvin cycle. 相似文献
34.
Analysis of total nitrogen, chlorophyll content, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and net photosynthesis rate was carried out on the leaves that support the developing pods in pigeon pea [ Cajanus cajan (L.) Millsp. cv. Prabhat] at several stages during pod filling. A continuous loss in all the above-mentioned parameters was observed during the course of pod development. When no pods were allowed to develop by continuous flower removal treatment, there was a considerable delay in loss of all these metabolic parameters. Excision of pods after their mid-development resulted not only in no further loss, but also in a significant recovery both of total nitrogen and of other investigated characteristics. 相似文献
35.
Using isolated pea thylakoids, the relative rate of QA
- oxidation has been estimated under various conditions, from the restoration of the induction curves following a dark period and from light 1-induced changes in modulated chlorophyll fluorescence excited by light 2.Alterations of
QinfA
sup–
oxidation rates were observed under conditions which affected the degree of thylakoid stacking, the lipid fluidity and the integrity of the membranes. The results are discussed in terms of the interactions between QA
- and the plastoquinone pool with particular emphasis on lateral diffusion.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- EDTA
Ethylenediaminetetracetate
- Hepes
N-2-hydroxyethyl piperazine-N-2-ethanesulphonic acid
- NADP
nicotinamide adenine dinucleotide phosphate 相似文献
36.
Abstract The chloroplast ultrastructure, especially the thylakoid organization, the polypeptide composition of the thylakoid membranes and photosynthetic O2 evolution rate, chlorophyll (Chl) content and Chi a/b ratio were studied in leaves of nine plants growing in contrasting biotopes in the wild in South Finland. All the measurements were made at the beginning of the period of main growth on leaves approaching full expansion, when the CO2-saturated O2 evolution rate (measured at 20°C and 1500 μmol photons m?2s?1) was at a maximum, ranging from 19.2 to 6.9 μmol O2 cm?2 h?1. Among the species, the Chi a/b ratio varied between 3.75 and 2.71. In the mesophyll chloroplasts, the ratio of the total length of appressed to non-appressed thylakoid membranes varied between 1.07 and 1.79, the number of partitions per granum varied between 2.8 and 12.0 and the grana area between 21 and 42% of the chloroplast area. There was a significant relationship between the rate of O2 evolution of the leaf discs and the thylakoid organization in the mesophyll chloroplasts. The higher the O2 evolution rate, the lower was the ratio of the total length of appressed to non-appressed thylakoid membranes and also the lower the grana area. Although the relationship of the photosynthetic rate with the Chi content and the Chi a/b ratio of the leaves was not as clear, a significant negative correlation existed between the Chi a/b ratio and the ratio of appressed to non-appressed thylakoid membranes, indicating lateral heterogeneity in the distribution of different Chl- protein complexes. 相似文献
37.
Detection of rapid induction kinetics with a new type of high-frequency modulated chlorophyll fluorometer 总被引:21,自引:0,他引:21
U. Schreiber 《Photosynthesis research》1986,9(1-2):261-272
A newly developed modulation fluorometer is described which operates with 1 sec light pulses from a light-emitting diode (LED) at 100 KHz. Special amplification circuits assure a highly selective recording of pulse fluorescence signals against a vast background of non-modulated light. The system tolerates ratios of up to 1:107 between measuring light and actinic light. Thus it is possible to measure the dark fluorescence yield and record the kinetics of light-induced changes. A high time resolution allows the recording of the rapid relaxation kinetic following a saturating single turnover flash. Examples of system performance are given. It is shown that following a flash the reoxidation kinetics of photosystem II acceptors are slowed down not only by the inhibitor DCMU, but by a number of other treatments as well. From a light intensity dependency of the induction kinetics the existence of two saturated intermediate levels (I1 and I2) is apparent, which indicates the removal of three distinct types of fluorescence quenching in the overall fluorescence rise from F0 to Fmax.Abbreviations QA and QB
consecutive electron acceptors of photosystem II
- PS II
photosystem II
- P 680
reaction center chlorophyll of photosystem II
- F0
minimum fluorescence yield following dark adaptation
- Fmax
maximum fluorescence yield
- DCMU
3-(3, 4-dichlorophenyl)-1, 1-dimethyl-urea
- DCCD
N,N-dicyclohexylcarbodiimide
- PQ
plastoquinone
- DAD
diaminodurene
Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement. 相似文献
38.
A chlorophyll b-less mutant of Chlamydomonas reinhardtii (Pg
27) was isolated after UV irradiation of the wild type cells. This photosynthetically competent mutant totally lacks chlorophyll b and the CP2 chlorophyll-protein complex. However, SDS-PAGE, proteolytic digestions and immunodetections demonstrated that the 24–25 Kd apoproteins of the lacking CP2 complex are still present in thylakoids of the Pg27 mutant. It is concluded that this CP2-less mutant is affected in the biosynthesis pathway of chlorophyll b.This CP2-less mutant was crossed with a CP1-less mutant (Fl5) Fluorescence emission spectra and fluorescence inductions in the presence of DCMU were analysed in the resulting (cp
2
–
, cp
1
+
), (cp
2
+
, cp
1
–
), (cp
2
+
, cp
1
+
), cp
2
–
, cp
1
–
)tetratype. Differences in PS 2 optical cross section and in the relative amplitude or localisation of fluorescence emission peaks fit well with a quadripartite model where PS1 and PS2 would each correspond to a reaction centre core complex (CP1 and CP2 respectively) associated to a light harvesting antenna (LHC1 and LHC2 respectively). The occurrence of energy transfers from PS1 peripheral antenna to PS2 in the Fl
5 mutant shows that, in absence of CP1, at least a part of its associated PS1 light harvesting antenna migrates in the PS2 containing appressed thylakoids.Abbreviations Chl
Chlorophyll
- LHC
Light harvesting chl a/b complex
- CP2
Predominant form of LHC or SDS polyacrylamide gels
- WT
Wild type
- DM
Double mutant (cp
1
–
, cp
2
–
)
- SDS-PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis
- DOC-PAGE
Deoxycholate polyacrylamide gel electrophoresis 相似文献
39.
In intact, uncoupled type B chloroplasts from spinach, added ATP causes a slow light-induced decline () of chlorophyll a fluorescence at room temperature. Fluorescence spectra were recorded after fast cooling to 77 K and normalized with fluorescein as an internal standard. Related to the fluorescence quenching at room temperature, an increase in Photosystem (PS) I fluorescence (F735) and a decrease in PS II fluorescence (F695) were observed in the low-temperature spectra. The change in the ratio was abolished by the presence of methyl viologen. Fluorescence induction at 77 K of chloroplasts frozen in the quenched state showed lowered variable (Fv) and initial (F0) fluorescence at 690 nm and an increase in F0 at 735 nm. The results are interpreted as indicating an ATP-dependent change of the initial distribution of excitation energy in favor of PS I, which is controlled by the redox state of the electron-transport chain and, according to current theories, is caused by phosphorylation of the light-harvesting complex. 相似文献
40.
The effect of 2-(n-heptyl)-4-hydroxyquinoline N-oxide (HQNO) on the kinetics of cytochrome b-563 and cytochrome c2 turnovers following single-turnover flashes was measured in isolated heterocysts. Low concentrations of HQNO (below 3 μM) blocked reoxidation of cytochrome b-563, whereas higher concentrations (above 5 μM) resulted in additional inhibition of cytochrome b-563 oxidation and also inhibited reduction of cytochrome b-563 and cytochrome c. Similar effects on cytochrome b-563 reduction and reoxidation were obtained with a combination of 5 μM HQNO and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (1–7 μM). In HQNO-inhibited heterocysts, cytochrome c reduction following a flash occurred in three phases with half-times of 0.5, 2.8 and 45 ms. The second phase nearly equalled the cytochrome b-563 reduction in half-time and magnitude. In the presence of HQNO, the reoxidation of cytochrome b-563 following two closely spaced actinic flashes displayed biphasic kinetics. The two phases correspond to reoxidation of cytochrome b-563 in which one or both of the cytochrome b-563 hemes in the cytochrome b–f complex are reduced. These results are interpreted in terms of a Q-loop in which HQNO, at low concentrations, blocks the site of rapid cytochrome b-563 reoxidation and at higher concentrations, also inhibits the site of electron donation by plastoquinol to the cytochrome b-f complex. 相似文献