共查询到20条相似文献,搜索用时 31 毫秒
1.
Most plants growing in temperate desert zone exhibit brief temperature-induced inhibition of photosynthesis at midday in the
summer. Heat stress has been suggested to restrain the photosynthesis of desert plants like Alhagi sparsifolia S. It is therefore possible that high midday temperatures damage photosynthetic tissues, leading to the observed inhibition
of photosynthesis. In this study, we investigated the mechanisms underlying heat-induced inhibition of photosynthesis in A. sparsifolia, a dominant species found at the transition zone between oasis and sandy desert on the southern fringe of the Taklamakan
desert. The chlorophyll (Chl) a fluorescence induction kinetics and CO2 response curves were used to analyze the thermodynamic characters of both photosystem II (PSII) and Rubisco after leaves
were exposed to heat stress. When the leaves were heated to temperatures below 43°C, the initial fluorescence of the dark-adapted
state (Fo), and the maximum photochemical efficiency of PSII (Fv/Fm), the number of active reaction centers per cross section (RCs) and the leaf vitality index (PI) increased or declined moderately.
These responses were reversed, however, upon cooling. Moreover, the energy allocation in PSII remained stable. The gradual
appearance of a K point in the fluorescence curve at 48°C indicated that higher temperatures strongly impaired PSII and caused
irreversible damage. As the leaf temperature increased, the activity of Rubisco first increased to a maximum at 34°C and then
decreased as the temperature rose higher. Under high-temperature stress, cell began to accumulate oxidative species, including
ammoniacal nitrogen, hydrogen peroxide (H2O2), and superoxide (O2
·−), suggesting that disruption of photosynthesis may result from oxidative damage to photosynthetic proteins and thylakoid
membranes. Under heat stress, the biosynthesis of nonenzyme radical scavenging carotenoids (Cars) increased. We suggest that
although elevated temperature affects the heat-sensitive components comprising of PSII and Rubisco, under moderately high
temperature the decrease in photosynthesis is mostly due to inactivation of dark reactions. 相似文献
2.
Syntrichia caninervis Mitt. is the dominant species in the moss crusts of the Gurbantunggut Desert, Northwestern China. We experimented with this
species under controlled environmental conditions. Modulated chlorophyll (Chl) fluorescence was used to test the speed of
recovery as evidenced by the time course of photosynthetic activity following remoistening. Transmission electron microscopy
was used to explore the cytological characteristics of the leaf cells. Minimum and maximum fluorescence (F0 and FM) and photosynthetic yield (FV/FM) of photosystem II (PSII) recovered quickly when shoots were remoistened in the dark. This was especially the case of FV/FM; within the first minute of remoistening this reached 90% or more of the value attained after 30 min. These physiological
changes were closely paralleled by cytological changes that indicated no damage to membranes or organelles. Correlation analysis
showed that Chl fluorescence decreased both above and below a narrow moisture optimum. Our results underline the capability
of S. caninervis to photosynthesize after remoistening. Utilizing precipitation events such as dew, fog, rain, and melting snow allows S. caninervis to survive and grow in a harsh desert environment. 相似文献
3.
Trehalose was supplied to wheat (Triticum aestivum L.) seedlings just before a high temperature (40 °C) treatment and some physiological parameters were measured during the heat stress and recovery. The application of trehalose decreased the net photosynthetic rate (PN) of wheat seedlings under the heat stress, but to a small extent increased the dry mass (DM) and leaf water content (LWC) after recovery from the heat stress. The trehalose-induced decrease in PN under the heat stress was not associated with a stomatal response. The heat stress slightly decreased the maximal efficiency of photosystem II (PS II) photochemistry (the variable to maximum chlorophyll a fluorescence ratio, Fv/Fm) similarly in the trehalose treated or non-treated plants. Under the heat stress, the actual efficiency of PS II photochemistry (ΦPSII) and the efficiency of excitation energy capture by open reaction centers (Fv′/Fm′) were lower in the trehalose-pretreated seedlings, whereas they were higher after the recovery. The patterns of changes in nonphotochemical quenching (NPQ) were contrary to those of ?PS II and Fv′/Fm′. The chlorophyll content was lower, whereas the β-carotene content and the degree of de-epoxidation (DEPS) of xanthophyll cycle pigments were higher in the trehalose-pretreated wheat seedlings under the heat stress. These results suggest that exogenous trehalose partially promotes recovery of wheat by the increase of NPQ, β-carotene content, and DEPS. 相似文献
4.
Artiom Bondarenco Gerhard Körtner Fritz Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2013,183(8):1113-1122
Bats are among the most successful groups of Australian arid-zone mammals and, therefore, must cope with pronounced seasonal fluctuations in ambient temperature (T a), food availability and unpredictable weather patterns. As knowledge about the energy conserving strategies in desert bats is scant, we used temperature-telemetry to quantify the thermal physiology of tree-roosting inland freetail bats (Mormopterus species 3, 8.5 g, n = 8) at Sturt National Park over two summers (2010–2012), when T a was high and insects were relatively abundant. Torpor use and activity were affected by T a. Bats remained normothermic on the warmest days; they employed one “morning” torpor bout on most days and typically exhibited two torpor bouts on the coolest days. Overall, animals employed torpor on 67.9 % of bat-days and torpor bout duration ranged from 0.5 to 39.3 h. At any given T a, torpor bouts were longer in Mormopterus than in bats from temperate and subtropical habitats. Furthermore, unlike bats from other climatic regions that used only partial passive rewarming, Mormopterus aroused from torpor using either almost entirely passive (68.9 % of all arousals) or active rewarming (31.1 %). We provide the first quantitative data on torpor in a free-ranging arid-zone molossid during summer. They demonstrate that this desert bat uses torpor extensively in summer and often rewarms passively from torpor to maximise energy and water conservation. 相似文献
5.
Variable chlorophyll a (Chl a) fluorescence is composed of a photochemical and a thermal phases of similar amplitudes. The photochemical phase can be induced
by a saturating single turnover flash (STF) and reflects the reduction of the Photosystem II (PS II) QA primary electron acceptor. The thermal phase requires multiple turnover flash (MTF) and is somehow related to the reduction
of the plastoquinone (PQ) molecules. This article aimed to determine the relative contributions of the QB-bound and the free oxidized PQ molecules to the thermal phase of Chl a fluorescence. We thus measured the interactive effects of exogenous PQ (PQex), of an inhibitor (DCMU) acting at the QB site of PS II and of an artificial quencher, 2-methyl-1,4-naphtoquinone, on Chl a fluorescence levels induced by STF (FF) and MTF (FM) in spinach thylakoids. We observed that: (1) the incorporation of PQex in thylakoids stimulated photosynthetic electron
transport but barely affected FF and FM in the absence of DCMU; (2) DCMU significantly increased the amplitude of FF but slightly quenched FM; (3) 2-methyl-1,4-naphtoquinone quenched FM to a larger-extent than FF; (4) DCMU increased the quenching effects of PQex on FF and FM and also, of methyl-1,4-naphtoquinone on FF. These results indicate that: (1) the QB-bound and the free PQ molecules contribute to about 56% and 25%, respectively, to the thermal phase Chl a fluorescence in dark-adapted thylakoids; and (2) the thermal phase of Chl a fluorescence is more susceptible than the photochemical phase to the non-photochemical quenching effect of oxidized quinones.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
《Comparative biochemistry and physiology. A, Comparative physiology》1989,92(3):393-402
- 1.1. Diurnal cycles of body temperature, Tb, and energy metabolism, M, at different ambient temperatures (Ta: +5 −+ 32°C) were tested in 13 sunbird species from various habitats and of different body masses (5.2–14.2 g) including one of the smallest passerines, Aethopyga christinae.
- 2.2. Resting M-level (night) reaches Ta-dependent mean values of 54% (+5°C) and 49% (+25°C) of activity M-levels (day). Expected level is ca 75%.
- 3.3. Resting metabolic rate of sunbirds lies within the range of theoretically expected values for birds.
- 4.4. Mean linear metabolism-weight regression of the night values follows: M = 0.102 × W0.712 (M = energy metabolism in kJ/hr and W = body mass in g).
- 5.5. Thermal conductances, Tc, are lower (−24%) than the predicted values. This is caused by a decrease of Tb at low Ta. Mean nocturnal Tc is 3.2 J/g × hr × °C, mean day-time value is 4.3 J/g × hr × °C.
- 6.6. The zone of thermoneutrality is, in most species, within a Ta-range of 24–28°C.
- 7.7. Normal day and night levels of Tb are in the same range as reported for other birds of the same weight class. Tb decreases slightly with falling Ta (partial heterothermia). Lowest recorded Tb was 34.2°C.
- 8.8. No species tested showed any sign of torpor at night, independent of Ta, body mass or habitat origin.
7.
Photosynthesis rate (An) becomes unstable above a threshold temperature, and the recovery upon return to low temperature varies because of reasons not fully understood. We investigated responses of An, dark respiration and chlorophyll fluorescence to supraoptimal temperatures of varying duration and kinetics in Phaseolus vulgaris asking whether the instability of photosynthesis under severe heat stress is associated with cellular damage. Cellular damage was assessed by Evans blue penetration (enhanced membrane permeability) and by H2O2 generation [3,3′‐diaminobenzidine 4HCl (DAB)‐staining]. Critical temperature for dark fluorescence (F0) rise (TF) was at 46–48 °C, and a burst of respiration was observed near TF. However, An was strongly inhibited already before TF was reached. Membrane permeability increased with temperature according to a switch‐type response, with enhanced permeability observed above 48 °C. Experiments with varying heat pulse lengths and intensities underscored the threshold‐type loss of photosynthetic function, and indicated that the degree of photosynthetic deterioration and cellular damage depended on accumulated heat‐dose. Beyond the ‘point of no return’, propagation of cellular damage and reduction of photosynthesis continued upon transfer to lower temperatures and photosynthetic recovery was slow or absent. We conclude that instability of photosynthesis under severe heat stress is associated with time‐dependent propagation of cellular lesions. 相似文献
8.
Verena Schoepf Andréa G. Grottoli Stephen J. Levas Matthew D. Aschaffenburg Justin H. Baumann Yohei Matsui Mark E. Warner 《Proceedings. Biological sciences / The Royal Society》2015,282(1819)
Mass bleaching events are predicted to occur annually later this century. Nevertheless, it remains unknown whether corals will be able to recover between annual bleaching events. Using a combined tank and field experiment, we simulated annual bleaching by exposing three Caribbean coral species (Porites divaricata, Porites astreoides and Orbicella faveolata) to elevated temperatures for 2.5 weeks in 2 consecutive years. The impact of annual bleaching stress on chlorophyll a, energy reserves, calcification, and tissue C and N isotopes was assessed immediately after the second bleaching and after both short- and long-term recovery on the reef (1.5 and 11 months, respectively). While P. divaricata and O. faveolata were able to recover from repeat bleaching within 1 year, P. astreoides experienced cumulative damage that prevented full recovery within this time frame, suggesting that repeat bleaching had diminished its recovery capacity. Specifically, P. astreoides was not able to recover protein and carbohydrate concentrations. As energy reserves promote bleaching resistance, failure to recover from annual bleaching within 1 year will likely result in the future demise of heat-sensitive coral species. 相似文献
9.
《Environmental and Experimental Botany》2005,53(2):205-214
Photosynthesis, transpiration, stomatal conductance and chlorophyll fluorescence characteristics were examined in kidney bean plants, with developing gradually water stress for several days after watering and then permitted to recover by re-watering. The photosynthetic rate, transpiration rate, and stomatal conductance decreased rapidly by withholding water for 2 days. The Fv/Fm of chlorophyll fluorescence characteristics slightly decreased when the water was withheld for 7 days. After re-watering the rate of recovery of photosynthesis, transpiration, and stomatal conductance decreased gradually as the days without watering became longer. The differences existed in rates of recovery of photosynthesis, transpiration, and stomatal conductance following drought stress. Among the fractional recoveries the highest was photosynthesis, and the lowest was stomatal conductance. Photosynthesis rate following drought stress was rapidly recovered until 2 days after re-watering, then recovered slowly. The critical time for the recovery of photosynthesis was recognized. The results show clearly a close correlation between the leaf water potential and the recovery level and speed of photosynthesis, transpiration, and stomatal conductance. 相似文献
10.
The possibility to improve the recovery of sugar beet plants after water stress by application of synthetic cytokinins N6-benzyladenine (BA) or N6-(m-hydroxybenzyl)adenosine (HBA) was tested. Relative water content (RWC), net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), chlorophyll (Chl) a and Chl b contents, and photosystem 2 efficiency characterized by variable to maximal fluorescence ratio (Fv/Fm) were measured in control plants, in water-stressed plants, and after rehydration (4, 8, 24, and 48 h). Water stress markedly decreased parameters of gas exchange, but they started to recover soon after irrigation. Application of BA or HBA to the substrate or sprayed on leaves only slightly stimulated recovery of PN, E, and gs in rehydrated plants, especially during the first phases of recovery. Chl contents decreased only under severe water stress and Fv/Fm ratio was not significantly affected by water stress applied. Positive effects of BA or HBA application on Chl content and Fv/Fm ratio were mostly not observed. 相似文献
11.
Response of chlorophyll fluorescence parameters to drought stress in sugar beet seedlings 总被引:1,自引:0,他引:1
We compared the parameters of chlorophyll fluorescence between two sugar beet (Beta vulgaris L.) species differing in drought tolerance. Our results indicated that there were different responses to the drought stress of these sugar beet species. In drought-tolerant sugar beet, the F 0 increased slightly, while qN increased substantially, indicating that these plants can protect PSII reaction centers from the damage. F v/F m and qP decreased slightly during the initial period of drought stress; this suggests that there is a slight impact of drought stress on the openness of PSII reaction centers, and thus the plants did not suffer seriously. This was further shown by the decreased Yield and electron transfer rate. The parameters of chlorophyll fluorescence were stable and can be used as an important indicator for sugar beet seedlings in the early drought tolerance. 相似文献
12.
Payu Pansarakham Paweena Pongdontri Piyada Theerakulpisut Anoma Dongsansuk 《Acta Physiologiae Plantarum》2018,40(9):173
Heat stress impacts the quantity and quality of rice grains, particularly during grain-filling stage needed for grain development. In this study, the effect of short heat stress (42 °C, 30 min) on indica rice plants at the grain-filling stage (dough grain stage) was found by determining their physiological and growth traits Fv/Fm, ?F/Fm′, chlorophyll content, leaf water potential (LWP), membrane stability, relative leaf area (RLA), relative plant height (RPH), total grain weight per panicle (TGW) and 1000 GW. Thai economic rice cvs. KDML105 and Pathumthani 1 (PTT1) were compared to the heat-tolerant rice cultivars N22 and Dular and to the heat-sensitive rice cultivar IR64. The results showed that short heat stress exhibited effects on physiology and growth greater than the control (35 °C, 30 min) by reducing of Fv/Fm, ?F/Fm′, chlorophyll content, LWP, membrane stability and RLA. This result impacted the TGW and 1000 GW. A higher reduction of physiological traits was shown in IR64, followed by KDML105. In contrast, N22 and Dular were minimally affected by heat stress and were able to adapt and recover based on their grain weight that exhibited less of an effect. PTT1 was also impacted by heat stress similarly to Dular. Thus, short heat stress affected the physiological parameters of five rice cultivars at the dough grain stage. In addition, the five indica rice cultivars were classified into three groups: (1) the heat-tolerant group (N22, Dular and PTT1), (2) the moderately heat-tolerant group (KDML105), and (3) the heat-sensitive group (IR64) by PC-ORD program at 50% of similarity of the 13 physiological traits. 相似文献
13.
Viviane F. FavarettoCarlos A. Martinez Hilda H. SorianiRosa P.M. Furriel 《Environmental and Experimental Botany》2011,70(1):20-28
To investigate the ability of pioneer and late-successional species to adapt to a strong light environment in a reforestation area, we examined the activities of antioxidant enzymes in relation to photosystem II, chlorophyll a fluorescence and photosynthetic pigment concentration for eight tropical tree species grown under 100% (sun) and 10% (shade) sunlight irradiation. The pioneer (early-succession) species (PS) were Cecropia pachystachya, Croton urucurana, Croton floribundus and Schinus terebinthifolius. The non-pioneer (late succession) species (LS) were Hymenaea courbaril L. var. stilbocarpa, Esenbeckia leiocarpa, Cariniana legalis and Tabebuia roseo-alba. We observed a greater decline in the ratio of variable to maximum chlorophyll a fluorescence (Fv/Fm) under full sunlight irradiation in the late-successional species than in the pioneer species. The LS species most sensitive to high irradiance were C. legalis and H. courbaril. In LS species, chlorophyll a, chlorophyll b and total chlorophyll concentrations were higher in the shade-grown plants than in plants that developed under full sunlight, but in the PS species C. floribundus and C. pachystachya, we did not observe significant changes in chlorophyll content when grown in the two contrasting environments. The carotenoids/total chlorophyll ratio increased significantly when plants developed under high-sunlight irradiation, but this response was not observed in the PS species S.terebinthifolius and C. pachystachya. The improved performance of the pioneer species in high sunlight was accompanied by an increase in superoxide dismutase (SOD, EC 1.15.1.1) activity, though no light-dependent increase in the activity of ascorbate peroxidase (APX, EC 1.11.1.11) was observed. The activity of catalase (CAT, EC 1.11.1.6) was reduced by high irradiation in both pioneer and late-successional species. Our results show that pioneer species perform better under high-sunlight irradiation than late-successional species, as indicated by increased SOD activity and a higher Fv/Fm ratio. C. legalis was the LS species most susceptible to photoinhibition under full sunlight conditions. These results suggest that pioneer plants have more potential tolerance to photo-oxidative damage than late-successional species associated with the higher SOD activity found in pioneer species. Reduced photoinhibition in pioneer species probably results from their higher photosynthetic capacities, as has been observed in a previous survey carried out by our group. 相似文献
14.
Yayong Luo Xueyong Zhao Hao Qu Xiaoan Zuo Shaokun Wang Wenda Huang Yongqing Luo Min Chen 《Acta Physiologiae Plantarum》2014,36(2):381-388
Responses of plants exposed to drought and rewatering have been well documented; however, little is known concerning strategies of psammophyte to drought and rewatering under different soil nutrient regimes. For this study, Pennisetum centrasiaticum under two soil nutrient regimes was subjected to progressive drought and subsequent rewatering. Soil water status, gas exchange characteristics, chlorophyll a fluorescence characteristics as well as biomass traits were measured to investigate ecophysiological responses. Net photosynthesis rate (P n), stomatal conductance (g s), water use efficiency, maximum quantum efficiency of photosynthesis system II (PSII, F V/F M), electron transport flux per cross section (ET0/CS0), and performance index on cross section basis (PICS) were suppressed during drought periods for both nutrient regimes. Meanwhile, leaf intercellular CO2 concentration (C i ), minimal fluorescence intensity (F 0), and dissipated energy flux per cross section (DI0/CS0) increased. Reversible downregulation of PSII photochemistry and enhanced thermal dissipation of excess excitation energy (DI0/CS0) contributed to enhanced photo-protection in drought-stressed plants. Thus, the results indicate that P. centrasiaticum is capable of withstanding and surviving extreme drought events, and the recovery pattern of stressed P. centrasiaticum under both nutrient regimes was similar. However, fertilization increased the biomass and the variation in gas exchange and chlorophyll a fluorescence characteristics during drought periods. Additionally, fertilization accelerated the process of drought and aggravated stress under extreme drought events. Thus, the fertilization strategy used in P. centrasiaticum restoration should be carefully selected—fertilization may not always be beneficial. 相似文献
15.
Understanding the dynamics of upwelling systems, especially the interactions between nutrients and light, has benefited from the application of models of varying complexity. Validation of such models using unialgal cultures or field observations has often proven difficult, but short-term incubations of contained natural assemblages and use of instantaneous physiological indicators offer an alternative approach. In May and June 1996, phytoplankton communities deep in the euphotic zone were sampled from nearly identical physical environments. Replicate samples (20 l volume) were incubated on deck at 50% surface irradiance with either no nutrient additions (Controls) or additions of 20 μM nitrate (Enrichments). Over 24 h, variable fluorescence (F v:F m), nitrate reductase activity (NR), nutrients, chlorophyll a and particulate C and N were monitored. Initial chlorophyll a (~3 μg l?1), phosphate (~0.2 μM), nitrate (~1.5 μM) and silicate (~3 μM) were similar in both months. Changes in NR and F v:F m indicated clear physiological responses to changes in irradiance and added nitrate that differed between months. In May, Controls and Enrichments responded in the same way. F v:F m stayed constant (0.5), chlorophyll a increased slightly, and NR activity increased markedly in all samples. In contrast, in June, treatments responded quite differently. F v:F m was near the theoretical maximum (0.7–0.8) initially and remained constant in Enrichments, but fell sharply in Controls. Declines in controls were also seen for chlorophyll a, and NR activity. Thus, the addition of 20 μM nitrate had a significant effect even though ambient levels of nitrate (>1 μM) should not have been limiting. Small (<20 μm) flagellates predominated in the May samples, but in June large and chain-forming centric diatoms constituted a significant proportion of the phytoplankton community. We conclude that the response of a phytoplankton community to environmental changes can depend on factors that are poorly represented by bulk measurements of chlorophyll, nutrients and particulate elements. 相似文献
16.
Roland Prinzinger 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,157(6):801-806
Summary Breathing frequencyF
r of resting blue-naped mousebirdsUrocolius macrourus lies between 50–70 per min and correlates directly with ambient temperatureT
a and energy metabolismM. The nocturnal mean energy intake per breath varies between 5.6–17.7 mJ/g. At highT
a the birds show gular fluttering with a relatively constantF
r of about 460 min–1.M shows a constant absolute day-night difference of 25 J/g·h; the relative differences areT
a-dependent between 36–168% (lower values at lowerT
a). Thermal conductance is 2.10–2.15 J/g·h·°C (predicted 2.67), indicating a good insulation. Basal metabolic rate BMR is reduced by 63% compared to predicted values. At aT
a-range of +8–36 °C the birds are normothermic. Below this range nocturnalT
b andM decrease slightly with fallingT
a. The birds show partial heterothermia (shallow hypothermia). Clustering is an effective energy saving strategy which allows loweringM with keeping highT
b even at lowT
a.Oxygen-intake is controlled byF
r as well as by tidal volumeV
t inT
a-dependent changing portions.V
T can vary between 0.29–0.91 ml (mean value 49.7 ml).Abbreviations
T
a
ambient temperature
-
T
b
body temperature
-
M
energy metabolism
-
F
r
breathing frequency
-
V
T
tidal volume
- BMR
basal metabolic rate
- TNP
thermoneutral point 相似文献
17.
The rehydration characteristics of the desiccation-tolerantplantsCraterostigma wilmsii andMyrothamnus flabellifolia (homoiochlorophyllous)andXerophyta viscosa (poikilochlorophyllous) were studied todetermine differences among them. A desiccation-sensitive plant(Pisum sativum) was used as a control. Recovery of water content,quantum efficiency (FV/FM), photosynthetic pigments and chloroplastultrastructure as well as damage to the plasmamembrane werestudied. P. sativum did not recover after desiccation and considerabledamage occurred during rehydration. The desiccation-tolerantplants appeared to differ in their responses to dehydrationand rehydration. The small herbaceousC. wilmsii generally showedlittle damage in the dry state and recovered faster than theother tolerant species.M. flabellifolia took longer to recoverthanC. wilmsii probably due to the presence of a woody stemin which dehydration-induced xylem embolisms slowed the rateof recovery. The poikilochlorophyllous speciesX. viscosa tookthe longest to recover because it took longer to reconstitutethe chloroplasts and the photosynthetic pigments. Quantum efficiencyrecovered in all species before water content and chlorophyllcontent recovered to control levels. The significance of thesedifferent responses to desiccation and recovery from desiccationis discussed. Desiccation-tolerant; FV/FM; homoiochlorophyllous; poikilochlorophyllous; chlorophyll; chloroplast; ultrastructure; Craterostigma wilmsii ; Myrothamnus flabellifolia ; Xerophyta viscosa ;Pisum sativum 相似文献
18.
The 24 hour recovery kinetics from n starvation in Phaeodactylum tricornutum and Emiliania huxleyi
下载免费PDF全文
![点击此处可从《Journal of phycology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The response of N (nitrate) starved cells of the diatom Phaeodactylum tricornutum and the coccolithophore Emiliania huxleyi to a pulse of new N were measured to investigate rapid cellular and photosynthetic recovery kinetics. The changes of multiple parameters were followed over 24 h. In P. tricornutum, the recovery of Fv/Fm (the maximum quantum yield of PS II) and σPSII (the functional absorption cross‐section for PSII) started within the first hour, much earlier than other parameters. Cellular pigments did not recover during the 24 h but the chlorophyll (chl) a/carotenoid ratios increased to levels measured in the controls. Cell division was independent of the recovery of chl a. In E. huxleyi, the recovery of Fv/Fm and σPSII started after an hour, synchronous with the increase in cellular organic N and chl a with pigments fully recovered within 14 h. P. tricornutum prioritized the recovery of its photosynthetic functions and cell divisions while E. huxleyi did not follow this pattern. We hypothesize that the different recovery strategies between the two species allow P. tricornutum to be more competitive when N pulses are introduced into N‐limited water while E. huxleyi is adapted to N scarce waters where such pulses are infrequent. These findings are consistent with successional patterns observed in coastal environments. This is one of only a few studies exploring recovery kinetics of cellular functions and photosynthesis after nitrogen stress in phytoplankton. Our results can be used to enhance ecological models linking phytoplankton traits to species diversity and community structure. 相似文献
19.
Joseph B. Williams Mohammed Shobrak Thomas M. Wilms Ibrahim A. Arif Haseeb A. Khan 《Saudi Journal of Biological Sciences》2012,19(2):121-130
Global warming is occurring at an alarming rate and predictions are that air temperature (Ta) will continue to increase during this century. Increases in Ta as a result of unabated production of greenhouse gases in our atmosphere pose a threat to the distribution and abundance of wildlife populations worldwide. Although all the animals worldwide will likely be affected by global warming, diurnal animals in the deserts will be particularly threatened in the future because Tas are already high, and animals have limited access to water. It is expected that Saudi Arabia will experience a 3–5 °C in Ta over the next century. For predicting the consequences of global warming for animals, it is important to understand how individual species will respond to higher air temperatures. We think that populations will not have sufficient time to make evolutionary adjustments to higher Ta, and therefore they will be forced to alter their distribution patterns, or make phenotypic adjustments in their ability to cope with high Ta. This report examines how increases in Ta might affect body temperature (Tb) in the animals of arid regions. We chose three taxonomic groups, mammals, birds, and reptiles (Arabian oryx, Arabian spiny-tailed lizard, vultures, and hoopoe larks) from Saudi Arabia, an area in which Ta often reaches 45 °C during midday in summer. When Ta exceeds Tb, animals must resort to behavioral and physiological methods to control their Tb; failure to do so results in death. The observations of this study show that in many cases Tb is already close to the upper lethal limit of around 47° C in these species and therefore allowing their Tb to increase as Ta increases are not an option. We conclude that global warming will have a detrimental impact on a wide range of desert animals, but in reality we know little about the ability of most animals to cope with change in Ta. The data presented should serve as base-line information on Tb of animals in the Kingdom for future scientists in Saudi Arabia as they explore the impact of global warming on animal species. 相似文献
20.
《Journal of thermal biology》1999,24(1):43-50
(1) The thermal capabilities of Australian silvereyes (Zosterops lateralis, 11 g) were investigated both at low and high ambient temperatures (Ta) during the photophase and scotophase. (2). The peak metabolic rate (PMR) induced by helium–oxygen (79:21 %, He–O2) exposure during the photophase was 15.64±1.55 mL O2 g−1 h−1 at an effective lower survival limit Ta (Tpmr) of −39.7±6.1°C. (3). Above the thermoneutral zone (TNZ), metabolic rate, body temperature (Tb), and thermal conductance increased steeply, but they were able to withstand a Ta of 39°C. (4). Our study shows that silvereyes are able to tolerate an impressive range of Ta from about −42°C to at least +39°C and are able to produce enough heat to maintain a thermal difference between Tb and Ta of up to 80°C. 相似文献