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1.
Stomatal movement and potassium transport in epidermal strips of Zea mays: The effect of CO2 总被引:1,自引:1,他引:0
C. K. Pallaghy 《Planta》1971,101(4):287-295
Summary The correlation between stomatal action and potassium movement in the epidermis of Zea mays was examined in isolated epidermal strips floated on distilled water. Stomatal opening in the isolated epidermis is reversible in response to alternate periods of light or darkness, and is always correlated with a shift in the potassium content of the guard cells. K accumulates in guard cells during stomatal opening, and moves from the guard cells into the subsidiary cells during rapid stomatal closure. When epidermal strips are illuminated in normal air, as against CO2-free air, the stomata do not open and there is a virtually complete depletion of K from the stomatal apparatus. In darkness CO2-containing air inhibits stomatal opening and K accumulation in guard cells, but does not lead to a depletion of K from the stomata as observed in the light. 相似文献
2.
At Ruiru, Kenya, 14CO2 was fed to single leaves at different distances from the apex on branches of mature fruiting and non-fruiting trees of Coffea arabica on six occasions from the Short Rains (November) 1966 to the Long Rains (April-May) 1967. The location of 14C-labelled assimilates in the treated branches was determined 26 h later by autoradiography. The direction of movement of labelled assimilates indicated large seasonal differences in the relative sink strengths of the shoot tip, fruit and trunk-root systems. On vegetative trees the sink strength of trunk-roots was much smaller, as compared with the shoots, at the beginning of the Long Rains than at the end of the previous Short Rains or in the intervening dry season. Assimilate use by growing fruits did not alter the pattern of distribution of assimilates to the other sinks at the end of the Short Rains, but it did restrict assimilate movement to both shoot tips and trunk-roots at the_ beginning of the Long Rains. In the dry season, virtually all assimilates were utilized by growing fruits when these were present. Vegetative secondary shoots provided assimilates to growing fruits and trunk-roots at the end of the Short Rains and in the dry season. Some practical implications are noted. 相似文献
3.
Effect of assimilate utilization on photosynthetic rate in wheat 总被引:7,自引:0,他引:7
Summary Two weeks after anthesis, when the grain is filling rapidly, the rate of photosynthesis by flag leaves of wheat cv. Gabo was between 20 and 30 mg CO2 dm-2 leaf surface hour-1 under the conditions used. About 45% of flag-leaf assimilates were translocated to the ear, and only about 12% to the roots and young shoots.On removing the ear, net photosynthesis by the flag leaves was reduced by about 50% within 3–15 hours, and there was a marked reduction in the outflow of 14C-labelled assimilates from the flag leaves.Subsequent darkening of all other leaves on plants without ears led to recovery of flag-leaf photosynthesis, as measured by gas analysis and 14CO2 fixation, and to increased translocation of assimilates to the roots and young shoots. Minor changes in the rates of dark respiration accompanied these major, reversible changes in photosynthetic rate.After more than a week in continuous, high-intensity light, the rate of photosynthesis by flag leaves of intact plants had fallen considerably, but could be restored again by a period in darkness, or by inhibiting photosynthesis in the ears by spraying them with DCMU. The inhibition of ear photosynthesis increased translocation of labelled assimilates from the flag leaf to the ears, without affecting leaf sugar levels.The application of TIBA to the culm below the ear inhibited auxin movement throught the culm, but had no influence on flag-leaf photosynthesis.These results suggest that, at least in this system, photosynthesis by the flag leaf is regulated directly by the demand for assimilates from the flag leaf and not indirectly through action in the leaf of auxins produced by the sink organs. 相似文献
4.
M. J. C. ASHER 《The Annals of applied biology》1972,72(2):161-167
The uptake of 14C and movement of 14C-labelled assimilates in wheat plants inoculated with Ophiobolus graminis was examined following exposure of the second youngest leaf to 14CO2. Autoradiographs of plants with infected seminal roots showed that assimilates were not translocated past the sites of root infection but accumulated in the undamaged portions of infected root systems, in particular the developing crown roots. There was no evidence that assimilates accumulated in the vicinity of O. graminis lesions. The net assimilation of 14CO2 by wheat plants over a 5 h feeding period was not significantly affected by O. graminis infection. However, infection reduced the amount of 14C lost through respiration. Infection delayed the transfer of labelled assimilates from the fed leaf to the remainder of the plant but increased the proportion translocated to the roots. The latter effect was not apparent when infected plants were continuously irrigated during, and for 20 h following, the feeding period. 相似文献
5.
Holding young rose shoots (Rosa hybrida cv. Marimba) in darkness while the rest of the plant was in light reduced the amount of 14C assimilates recovered from the darkened shoot by half. Relative specific activity of the shoot tip grown in light was 13.5 times greater than that of the darkened one. The flower bud at the shoot tip degenerated in darkness and died. Shoots 2 to 3 centimeters long, after flower initiation, were most sensitive to the dark treatment. The degeneration is a gradual and reversible process in the first 8 days of darkness, followed by irreversible damage and atrophy. Darkening enhanced the ability of the young leaves to compete for the available assimilates over that of the darkened shoot tip. The enhancement of the mobilizing ability of the shoot tip by light is independent of photosynthesis since spraying with 3-(3,4-dichlorophenyl)-1,1-dimethylurea or holding shoots in a CO2-free atmosphere did not diminish the promoting effect of light on flower bud development or assimilate import. The possibility that light exerts its effect by photoproduction of ATP was also excluded inasmuch as no differences were found in ATP levels of shoot tips held in darkness and those held in light. 相似文献
6.
I. F. Wardlaw 《Planta》1972,104(1):18-34
Summary Localized cooling of a 2 cm length of the leaf blade of the grass Lolium temulentum to 0° C, had only a small effect on the mass transfer of assimilates from the distal part of the leaf. There was no evidence of a reduction in the velocity of movement of 14C-labelled assimilates through the low temperature zone, and the retention of assimilates along the pathway of movement was reduced by low temperature. In contrast to the longitudinal movement, lateral movement of 14C, induced by steam killing sections of the leaf, was extremely sensitive to temperature and showed no sign of acclimatization, even after 3 days at low temperature. These results suggest that, although loading sugars into the transport system was sensitive to temperature, the movement of assimilates was not directly controlled by metabolic processes along the pathway. 相似文献
7.
Source,sink and hormonal control of translocation in wheat 总被引:1,自引:0,他引:1
Summary An analysis of the pattern of movement of 14C-labelled flag leaf assimilates in wheat (Triticum aestivum l. c.v. Gabo) during grain development, indicated that the greater the requirement for assimilates by the ear the more rapid was the speed of movement of these through the peduncle to the ear and also the lower their concentration. Experiments with [14C] indoleacetic acid ([14C]IAA) suggested that auxin production by the grains was not responsible for the control of assimilate translocation through the peduncle. Limiting the supply of available assimilates by shading the lower parts of the plant, did not significantly alter the speed of movement of 14C-photosynthate through the peduncle, while severing half of the vascular tissue in the peduncle altered the pattern of movement of 14C to the ear and enhanced the speed of movement of 14C through the remaining functional conducting tissue. These results are discussed in relation to the mechanism of translocation. 相似文献
8.
Excised Albizzia leaflet pairs exposed to red (R) light close within 30–90 min after transfer to darkness. Interruption of darkness by far-red (FR) light at any time after R inhibits closure within ca. 10 min. Similarly, irradiation with R at any time after prior FR promotes closure within ca. 10 min, and the increased rate of closure is independent of the time lapse between the FR and R irradiations. Closure in the dark is inhibited by NaN3 and DNP (5 X 10–4 m ), by anaerobic conditions and by externally applied salts of monovalent cations, especially K; it is also temperature sensitive. Pulvinule cells are very high in K. Electron microprobe analysis of cryostated, lyophilized pulvinules reveals that during closure, K is lost from ventral cells and enters dorsal cells. FR before darkness inhibits the former but not the latter process. Thus, K flux appears to control the changes in volume of the pulvinule cells that control leaflet movement. While leaflet closure normally requires a dark period, salts of organic acids such as sodium acetate, propionate, and butyrate cause closure in the light. 相似文献
9.
Dubinina I. M. Burakhanova E. A. Kudryavtseva L. F. 《Russian Journal of Plant Physiology》2001,48(1):32-37
We studied the efflux of radioactive photosynthetic products from the central vacuole into the cytosol of protoplasts isolated from the mesophyll tissue of the sugar beet (Beta vulgaris L.) after their darkening and subsequent cessation of photosynthesis. Among the products accumulated in the vacuole were the 14C-labelled sugars malate and alanine, small amounts of citric, glutamic, and aspartic acids, and some other amino acids. During the initial 20–30 min of darkness, there was no substantial utilization of photoassimilates accumulated in the vacuole during the preceding light period. An efflux of assimilates occurred later, after 30–40 min of darkness. A decrease in the vacuolar 14C-sucrose occurred not only due to its exit into the cytosol but also because of its conversion into 14C-monosaccharides by the vacuolar invertase. In fact, this decrease in the sucrose content correlated well with the accumulation of monosaccharides. Immediately after photosynthesis ceased, the chloroplastic 14C-starch was utilized for the maintenance of cytoplasmic metabolism. After 30-min darkness, the content of starch in the chloroplasts decreased by several times. We believe that the vacuoles of sugar-beet mesophyll cells are transient reservoirs for assimilates and the products of their conversion (glucose and fructose), which can rapidly leave the vacuole to maintain homeostasis in the cytosol under varying environmental conditions. 相似文献
10.
Mature leaves of a variegated cultivar of Coleus blumei Benth. with a green border and central albino region constitute a source-sink system suitable for studies on assimilate partitioning. Leaves treated with 14CO2 on a small part of the intact green border export assimilate via the shortest path into the stem. Leaves with all but a small lobe of the green border removed show different partitioning of labeled assimilates when the leaf is exposed to 14CO2 (Fisher and Eschrich, 1985): The whole albino region of the leaf is supplied but no tracer is exported into the stem. When the green border is completely removed, 14CO2-treatment of the albino region leads to the fixation of CO2, obviously by PEP carboxylase, as indicated by the occurrence of labeled malate. Results show that the albino region of the variegated leaf constitutes a potential sink when deprived of its green border. In addition, CO2-fixation by PEP carboxylase in albino tissue seems to indicate a common capacity of leaves which is normally masked by photosynthesis. The difference of assimilate partitioning between leaves with intact and leaves with partly removed green borders demonstrates that the unlabeled assimilates control the movement of labeled assimilates. 相似文献
11.
Utilization of Photosynthates for Growth, Respiration, and Storage in Tops and Roots of Lolium multiflorum 总被引:2,自引:0,他引:2
G. K. HANSEN 《Physiologia plantarum》1978,42(1):5-13
Lolium multiflorum L. was grown in pots in controlled environments. CO2-exchange rates were continuously measured on two pots during 46 and 52 days, respectively, separating between tops and roots. After 20 days, the plants were entirely defoliated and the plants were then followed during the regrowth period. During the experiment, alternating 2–3 day periods of high and low irradiance were applied. Analogously treated plants were frequently harvested to obtain the distribution of assimilates between tops and roots. From integration of CO2-exchange rates, diurnal photosynthesis and respiration were obtained, and utilization of assimilates was analysed. The respiration associated with the synthesis of new structural material (growth respiration) was dependent on assimilates originating from both the current and the preceding 24 h diurnal cycles. The amount of new structural material synthesized during the current 24 h diurnal cycle was estimated from the relative contribution of assimilates accumulated from the preceding and the current 24 h and diurnal cycles to growth respiration of the current 24 h. From this approximation, the respiratory components connected to synthesis of new structural material and to maintenance of already established material were found. Growth and maintenance respirations of the tops were alike during the predefoliation and the regrowth periods. For the roots, however, growth respiration was higher and maintenance respiration lower in the regrowth period. The difference between daily integrated CO2-exchange and the amount converted into new structural material was assumed to be the daily change in assimilates stored. On the first day of a period of high irradiance, the assimilation per unit leaf weight was higher than on the following day of high irradiance, and an accumulation of storage material took place. On the first day of a period of low irradiance, the assimilation per unit leaf weight was lower than on the following day of low irradiance, and there was a depletion of assimilates stored. These effects were most pronounced during the regrowth period, indicating a change in the metabolic sink demand. This indicates a strong feedback mechanism between sources and sinks, in the sense that accumulation of products will inhibit assimilation. 相似文献
12.
The distribution of assimilates of 14CO2 in ethanol soluble and insoluble fractions was measured at 20-day intervals from 45–135 days after sowing (DAS) in chickpea (Cicer arietinum) grown at two moisture levels. The contribution of pre-flowering assimilates to pods, although very low, was higher under the stress conditions. At the time of harvest, the recovery of 14C in pods was 0.4 and 0.9% of the total 14C fed 45 DAS in soluble and 2.5 and 5.1% in insoluble fractions in control and stressed plants, respectively. The %14C received by nodules continuously decreased with increasing age of plants. Stressed plants diverted more 14C to nodules, compared to control, during vegetative and flowering stages. During active seed filling, stressed plants diverted more 14C to reproductive parts and less to nodules, compared to control. Significant amounts of 14C were retgined by the stem and leaves during the seed-filling period and it appears that there is scope for the remobilisation of pre-flowering, as well as post-flowering assimilates for seed-filling of chickpea. 相似文献
13.
Incubation experiments were carried out to evaluate the feasibility of extracting phosphorus from soil by embedding iron oxide-impregnanted filter paper strips (Pi strips) in soils having a wide range in pH, texture, and extractable-P contents. Under flooded conditions, the amount of P extracted by the Pi strips increased with the period of submergence and embedding time of the Pi strips. Under unsaturated conditions, the Pi strips were found to extract P from soils over a wide range in moisture conditions; however, keeping the soil at moisture level between saturation and field capacity was found to result in maximal sorption of P by the strips. An embedding time of 16 h was found to be adequate.Phosphorus extracted by embedding Pi strips in soil columns for 16 h at field capacity moisture level correlated significantly with P extracted by shaking the soil with 0.01 M CaCl2 solution and a Pi strip for 16 h in the laboratory (r=0.94**). The P extracted by embedding Pi strips correlated best with Bray 1 P in acid soils (r=0.97**) and with Olsen P in alkaline and calcareous soils (r=0.96**). The results of the studies demonstrate the feasibility of developing a nondestructive method of monitoring changes in plant-available P in situ under field conditions. 相似文献
14.
Marianna Max Michael Menaker 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(4):479-489
Summary The pineal gland of the rainbow trout, Salmo gairdneri, when kept under in vitro perifusion culture conditions, displays a consistently elevated level of melatonin production in darkness (Gern and Greenhouse 1988). Upon light exposure melatonin production falls and stabilizes at a new lower level that is dependent upon the irradiance of the stimulus. To achieve the maximal response for each irradiance, the duration of the stimulus must exceed 30 min. The response amplitude is maximally sensitive to photons presented over durations of 30–45 min; is very insensitive to shorter light exposures; and is maintained with no evidence of adaptation over longer exposures. Temperature plays a role in regulation of melatonin production both in darkness and during light exposure; increased temperature increases melatonin production in darkness and also increases the sensitivity of the response to light. The action spectrum for the response is best fit by the Dartnall nomogram for a vitamin A1 based rhodopsin with peak sensitivity near 500 nm. The possible adaptive significance of control of melatonin synthesis by light and temperature is considered.Abbreviations
LD
lightdark cycle
-
RIA
radioimmunoassay
-
I
125
Iodine
-
HIOMT
hydroxyindole-O-methyltransferase 相似文献
15.
Energy Supply for Stomatal Opening in Epidermal Strips of Commelina benghalensis 总被引:2,自引:1,他引:1
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Raghavendra AS 《Plant physiology》1981,67(2):385-387
The influence of light or darkness on stomatal opening in epidermal strips of Commelina benghalensis was evaluated in the presence or absence of O2 and/or metabolic inhibitors. Opening was restricted in nitrogen and was promoted by NADH and acids of the tricarboxylic acid cycle (succinate and α-ketoglutarate) in CO2-free air in light as well as in darkness. The enhancement by light of stomatal opening was prevalent under nitrogen or in the presence of the respiratory inhibitors (sodium azide and oligomycin). Respiratory inhibitors decreased the opening in light or darkness under CO2-free air but exhibited no effect under nitrogen, whereas phosphorylation uncouplers were inhibitory in light or darkness under both CO2-free air and nitrogen. The results suggest that oxidative phosphorylation is a basic source of energy for stomatal opening, although photophosphorylation could be an energy source. 相似文献
16.
Johannes Willenbrink 《Planta》1966,71(2):171-183
Zusammenfassung 6–10 min nach Beginn der 14CO2-Assimilation befindet sich 14C-Aktivität im Stiel des 14CO2-exponierten Blattes belichteter Pflanzen von Pelargonium zonale und Phaseolus vulgaris. Die Verteilungsrichtung der Assimilate im Sproß scheint vor allem durch das Alter des 14C-assimilierenden Blattes bestimmt, jedoch nicht einseitig festgelegt zu sein; geringe, aber faßbare Mengen an 14C-Saccharose wereden innerhalb von 20 min (bei Phaseolus) und 180 min (bei Pelargonium) auch aus relativ jüngeren in ältere Blätter transportiert.Neben 14C-Saccharose wurden im Blattstiel-und Stengelgewebe stets markierte Zuckerphosphate, Hexosen und organische Säuren nachgewiesen. Stärke war nur zu einem verschwindend geringen Anteil an der Gesamtmarkierung der analysierten Transportstrecken beteiligt.
Translocation of 14C-labelled assimilates in the phloem of Pelargonium zonale and Phaseolus vulgaris
Summary After the laminae of leaves of intact plants had been exposed to 14CO2 the translocation of 14C-labelled assimilates across the petioles starts very quickly: 6 to 10 min later 14C-activity could be detected in the basal part of the petioles. The way of distribution within the plant seems to be influenced mainly by the age of the 14CO2-assimilating leaf, however, but not in the sense of an unidirectional movement; little but distinct amounts of 14C were carried also from younger yet full expanded leaves down to older leaves, within 20 min (in Phaseolus) or 180 min (in Pelargonium). Besides sucrose, which was shown by paper chromatography to be the main form of assimilates translocated in these species, we identified sugar phosphates, hexoses, and some organic acids in the petiole and stem tissue as being radioactive also. In our experiments, the petiole segments did not contain any remarkable amount of 14C-labelled starch.相似文献
17.
Phytoplankton community dynamics are affected not only by atural events such as overwintering but also by artificial events such as artificial circulation and related darkness conditions. In order to clarify the effect of tolerance for prolonged darkness on community succession, laboratory cultures of three phytoplankton taxa, Microcystis aeruginosa(Cyanophyceae), Scenedesmus
quadricauda(Chlorophyceae), and Melosira
ambigua(Bacillariophyceae) were carried out in darkness. The period of darkness was varied: 5, 10, 15, 20 days, and the control. Thereafter, all samples were reilluminated. After more than 10 days of darkness, M. aeruginosa decreased markedly with the length of the darkness period and was reduced to only 1% of the initial cell number after 20 days darkness. In contrast, S. quadricauda and M. ambigua retained their biomass even after 20 days of darkness. After restarting the light–dark cycle, however, all three species similarly increased exponentially and reached their maximum biomass levels. These results suggest that differences in tolerance for prolonged darkness may cause the succession of the phytoplankton under certain conditions. 相似文献
18.
Rüdiger Riesch Michael Tobler Martin Plath Ingo Schlupp 《Environmental Biology of Fishes》2009,84(1):89-94
Life history traits within species often vary among different habitats. We measured female fecundity in mollies (Poecilia mexicana) from a H2S-rich cave and from a neighbouring surface habitat, as well as in laboratory-reared individuals of both populations raised
in either light or continuous darkness. Compared to conspecifics from surface habitats, cave-dwelling P. mexicana had reduced fecundity (adjusted for size) in the field. In the laboratory, the fecundity of surface mollies was higher in
light than in darkness, whereas fecundity in the cave mollies was almost unaffected by the ambient light conditions. Our results
suggest a heritable component to the reduction in fecundity in female cave mollies. Moreover, the reduced plasticity in fecundity
of cave mollies in response to light conditions might be an example of genetic assimilation or channelling of a life history
trait in a population invading a new environment. 相似文献
19.
AbstractLight and growth-promoting compounds, such as gibberellic acids (GA3), are among the most important factors that can break physiological seed dormancy. Here, we investigate the effects of GA3 and light on germination of five species of Resedaceae that are known to have different levels of physiological dormancy. Seeds were incubated at 20/30?°C in both 12-hr photoperiod and complete darkness. To study the effect of growth hormone on germination, seeds were soaked for 24?h in different concentrations of GA3 before sowing. The annuals (Reseda aucheri and Oligomeris linifolia) and the perennial Ochradenus arabicus had deep physiological dormancy, and exogenous application of GA3 enhanced their germination in the light, but not in darkness; few or no seeds germinated in the dark in these species. Ochradenus aucheri and O. baccatus had intermediate and non-deep dormancy, respectively, and application of GA3 enhanced their germination in both light and darkness. Germination of the annual species was much slower than that of the shrubby perennials. Overall, these results indicate that conditions under which seed developed, matured and stored on maternal plants as well as incubation conditions should be taken into consideration when assessing germination behavior of the perennial species of Resedaceae. 相似文献
20.
Barium chloride at 0.1 mM concentration inhibited elongation of mungbean (Phaseolus aureus) roots more strongly than elongation of hypocotyls. Root growth was completely inhibited at 80 mM and there was no germination
at 100 mM. Respiration rates which were directly proportional to seedling vigour declined at varying degrees at the growth-inhibitory
concentrations of BaCl2. Barium retarded senescence in isolated leaf discs ofCephalandra indica by maintaining the chlorophyll level in darkness. The carotenes were similarly protected from degradation by Ba in darkness
whereas xanthophylls were retained both in darkness and light. Ba also protected anthocyanin pigments in the staminode discs
ofCanna indica flowers and reduced to a variable extent the leakage of betacyanin pigment fromBeta vulgaris root discs caused by various membrane active chemicals. Applied either alone or in combination with IAA, Ba inhibited cell
enlargement in wheat (Triticum aestivum) coleoptile sections. Barium-induced inhibition of lettuce (Lactuca sativa) hypocotyl elongation was largely overcome by GA3. 相似文献