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1.
《Journal of Asia》2007,10(2):151-155
The susceptibility of Spodoptera litura to SlMNPV infection was markedly affected by phyto-chemicals ingested during the acquisition of viral inoculum on foliage of tomato and cauliflower. The LD50 values computed for second, third and fourth instar larvae assayed on tomato leaves were 254, 819 and 23395 PIBs/larva, respectively whereas, it was 326, 1719 and 43843 PIBs/larva for respective instars when assayed on cauliflower leaves. Thus LD50 values for second, third and fourth instar larvae were 1.28-, 2.09- and 1.87- fold lower, respectively in tomato leaves. Similarly, LT50 values for second, third and fourth instar larvae assayed on tomato leaves were 7.1 and 7.5 days, respectively at inoculum dose of 2.7×104 PIBs/larva whereas, it was 7.7 and 8.0 days for respective instars when assayed on cauliflower leaves at same inoculum. This result also showed that the S. litura were more susceptible on tomato leaves in comparison to cauliflower leaves as the time required for mortality was lower in tomato leaves. The possible biochemical bases for differential level of mortality of S. litura larvae on tomato and cauliflower crops needs to be investigated. 相似文献
2.
Photosynthetically active radiation (PhAR) is apparently the environmental factor having the greatest influence on leaf thickness for Plectranthus parviflorus Henckel (Labiatae). A four-fold increase in leaf thickness from 280 to 1170 μm occurred as the PhAR was raised from 1.3 to 32.5 mol m−2 day−1 . Compared to a constant PhAR of 2.5 mol m−2 day−1 , a PhAR of 32.5 mol m−2 day−1 for one week during the first week (with return to 2.5 mol m−2 day−1 during the second and third weeks) led to an increase in final leaf thickness by 323 μm (to 802 μm). When increased PhAR was applied during the second week the increase in final thickness over the control was 217 μm, and when increased PhAR was applied during the third week it was 99 μm. However, leaf thickness was not simply responding to total daily PhAR, since a leaf 450 μm thick could occur at a low instantaneous PhAR for a long daytime (total daily PhAR of 1.5 mol m−2 day−1 ) and at a high PhAR for a short daytime (4.5 mol m−2 day−1 ). Total daily CO2 uptake (net photosynthesis) was approximately the same in the two cases, suggesting that this is an important factor underlying the differences in leaf thickness. Leaf thickness is physiologically important, since thicker leaves tend to have greater mesophyll surface area per unit leaf area ( A mes / A ) and hence higher photosynthetic rates. 相似文献
3.
Joaquim A. G. Silveira José M. Júnior Evandro N. Silva Sérgio L. Ferreira-Silva Rafael M. Arag?o Ricardo A. Viégas 《Acta Physiologiae Plantarum》2012,34(5):1629-1637
This study establishes relationships between salt resistance and solute accumulation in roots and leaves of two contrasting cashew species. The sensitive (Anacardium microcarpum) and resistant (A. occidentale) species showed maximum root LD50 values (the external NaCl concentration required for a 50% reduction in dry weight) of 63 and 128?mM NaCl, whereas the shoot LD50 values were 90 and 132?mM, respectively. The salt sensitivity was directly associated with Na+ accumulation and especially with the Cl? content in leaves and to a minor extent in roots. The accumulation of saline ions was associated with higher net uptake rates by roots and transport rates from root to shoot in the sensitive cashew species. The K+/Na+ ratios were not associated with salt resistance either in roots or leaves. Proline and free amino acid concentrations were strongly increased by salinity, especially in the leaves of the resistant species. The soluble sugar concentrations were not influenced by NaCl treatments in leaves of both species. In contrast, the root soluble sugar content was significantly decreased by salinity in the sensitive species only. In conclusion, the higher salt sensitivity of A. microcarpum is associated to an inefficient salt exclusion system of the leaves, especially for Cl?. On the other hand, the resistant species displays higher concentrations of organic solutes especially a salt-induced accumulation of proline and free amino acids in leaves. 相似文献
4.
David Whitehead Kevin L. Griffin† Matthew H. Turnbull‡ David T. Tissue§ Victor C. Engel† Kim J. Brown† William S.F. Schuster¶ Adrian S. Walcroft 《Global Change Biology》2004,10(6):925-938
Measurements of photosynthesis and respiration were made on leaves in summer in a Quercus rubra L. canopy at approximately hourly intervals throughout 5 days and nights. Leaves were selected in the upper canopy in fully sunlit conditions (upper) and in the lower canopy (lower). In addition, leaves in the upper canopy were shaded (upper shaded) to decrease photosynthesis rates. The data were used to test the hypothesis that total night‐time respiration is dependent on total photosynthesis during the previous day and that the response is mediated through changes in storage in carbohydrate pools. Measurements were made on clear sunny days with similar solar irradiance and air temperature, except for the last day when temperature, especially at night, was lower than that for the previous days. Maximum rates of photosynthesis in the upper leaves (18.7 μmol m?2 s?1) were approximately four times higher than those in the lower leaves (4.3 μmol m?2 s?1) and maximum photosynthesis rates in the upper shaded leaves (8.0 μmol m?2 s?1) were about half those in the upper leaves. There was a strong linear relationship between total night‐time respiration and total photosynthesis during the previous day when rates of respiration were normalized to a fixed temperature of 20°C, removing the effects of temperature from this relationship. Measurements of specific leaf area, nitrogen and chlorophyll concentration and calculations of the maximum rate of carboxylation activity, Vcmax, were not significantly different between upper and upper shaded leaves 5 days after the shading treatment was started. There were small, but significant decreases in the rate of apparent maximum electron transport at saturating irradiance, Jmax (P>0.05), and light use efficiency, ? (P<0.05), for upper shaded leaves compared with those for upper leaves. This suggests that the duration of shading in the experiment was sufficient to initiate changes in the electron transport, but not the carboxylation processes of photosynthesis. Support for the hypothesis was provided from analysis of soluble sugar and starch concentrations in leaves. Respiration rates in the upper shaded leaves were lower than those expected from a relationship between respiration and soluble sugar concentration for fully exposed upper and lower leaves. However, there was no similar difference in starch concentrations. This suggests that shading for the duration of several days did not affect sugar concentrations but reduced starch concentrations in leaves, leading to lower rates of respiration at night. A model was used to quantify the significance of the findings on estimated canopy CO2 exchange for the full growing season. Introducing respiration as a function of total photosynthesis on the previous day resulted in a decrease in growing season night‐time respiration by 23% compared with the value when respiration was held constant. This highlights the need for a process‐based approach linking respiration to photosynthesis when modelling long‐term carbon exchange in forest ecosystems. 相似文献
5.
Photosynthetic parameters were studied in Arbutus unedo L. trees growing at either ambient (AC) or elevated EC (mean 465 μmol mol-1) CO2 concentration near a natural CO2 vent in Orciatico, Italy Diurnal courses of net photosynthetic rate (P
N), ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), and quantum yield of electron transport through photosystem 2 (Φ2) were measured on sun and shade leaves. The contents of N, C, Ca, K, P, and chlorophyll (Chl) and specific leaf area (SLA)
in these leaf categories were also determined. A morning peak and midday depression of P
N were found for both AC and EC sun leaves. Long-term EC caused little or no down-acclimation of P
N in sum leaves. The estimate of total daily CO2 uptake was lower in AC leaves than in EC leaves. In shade leaves, it reached up to 70 % of the value of sun leaves. The Fv/Fm ratio showed decreasing trend in the morning, reached a minimum at midday (90 % of dawn value), and then increased in the
afternoon. The EC had no effect on Fv/Fm either in sun or shade leaves. Plants grown near the CO2 spring had lower Chl content, higher SLA, and higher Ca and K contents than plants grown under AC.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
M.O. Odindo 《Journal of invertebrate pathology》1981,38(2):251-255
Third-instar Spodoptera exempta larvae were fed on young maize leaves treated with 20 μl of polyhedral inclusion body (PIB) suspension of concentrations that varied from 1.6 × 102 to 1.6 × 109 PIBs/ml. Daily observations were kept on mortality rates. A probit analysis on the results gave an LD50 value of 48.4 PIBs/larva (lower and upper fiducial limits 39.2 and 59.4 PIBs/larva, respectively), and an LT50 that varied from 146.2 to 221.3 hr, depending on the dosage. LD and LT values obtained show the high pathogenicity of S. exempta nuclear polyhedrosis virus to its host. 相似文献
7.
The susceptibility of Heliothis armiger larvae of different ages to a commercial nuclear polyhedrosis virus (NPV), Elcar, was determined by bioassay. The median lethal dosage (LD50) increased 150-fold during the first week of larval life at 25°C, i.e., during development to early fourth instar, but daily feeding rate and thus potential virus acquisition also increased. A linear relationship was determined between log LD50 and larval length, indicating that larval length constitutes a useful index for estimating the susceptibility of larval populations. Median lethal times (LT50s) were similar for larvae tested at ages of 0 to 7 days and ranged from 3.6 to 8.0 days at 30°C. The amount of virus produced in a single, infected neonate was equivalent to 1.4 × 106 LD50s for neonates, a 900,000-fold increase on the dose supplied. The data support the practice of directing the NPV against neonates, but, on the basis of larval susceptibility alone, the age of larvae at treatment may not always be critical. 相似文献
8.
Ibrahim A. Arif Anis Ahamed Radhakrishnan Surendra Kumar Akbar Idhayadhulla Aseer Manilal 《Saudi Journal of Biological Sciences》2019,26(4):673-680
The objective of this study was to investigate brine shrimp cytotoxicity, larvicidal, nematicidal, and antifeedant activities of novel piperidin-connected 2-thioxo-imidazolidin-4-one derivatives. The activities of target compounds were compared with some naturally occurring (?)-pinidinol, hydantocidin, and positive controls. Target compounds were synthesized via cyclocondensation method. The compounds were synthesized and then characterized by infrared spectroscopy, 1H NMR, 13C NMR, mass spectral, and elemental analyses. Brine shrimp cytotoxicity assay was investigated using freshly hatched, free-swimming nauplii of Artemiasalina. Larvicidal screening was performed against urban mosquito larvae (Culex quinquefasciatus). Nematicidal activity was evaluated using juvenile nematodes of Meloidogyne javanica. Regarding antifeedant activity, marine-acclimated Oreochromis mossambicus fingerlings were used. Compounds 3a-c (piperidin-connected 2-thioxoimidazolidin-4-one) were found to be lethal to the second instar larvae of mosquito, which produced LD50 values of 1.37, 6.66, 6.51 μg/mL, compared to compounds (?) pinidinol and hyantocidin LD50 values of 18.28 and 22.11 μg/mL respectively. Compound 3a-c was found to kill 100% of fish fingerlings within 6 h at 20 µg/mL, with LD50 values of 1.54, 1.79, 1.52 µg/mL, compared to compounds (?) pinidinol and hyantocidin with LD50 values of 10.21 and 21.05 μg/mL respectively. Compound 3c with LD50 value of 1.57 μg/mL demonstrated high nematicidal activity compared to compound 3a, 3b, (?) Pinidinol and Hyantocidin LD50 values of 6.45, 2.42, 14.25, 26.30 μg/mL respectively. Therefore, the 2-thioxoimidazolidin-4-one with piperidin ring showed high potential cytotoxic, larvicidal, nematicidal, and antifeedent activities. 相似文献
9.
Hartmut K. Lichtenthaler Fatbardha Babani Martin Navrátil Claus Buschmann 《Photosynthesis research》2013,117(1-3):355-366
The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively measured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional measurements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves. In these cases, we also determined in detail the pigment composition of all four leaf types. In addition, we determined the quantum irradiance and spectral irradiance of direct sunlight, blue skylight as well as the irradiance in half shade and full shade. The results indicate that sun leaves possess significantly higher mean values for the net CO2 fixation rates P N (7.8–10.7 μmol CO2 m?2 s?1 leaf area) and the Chl fluorescence ratio R Fd (3.85–4.46) as compared to shade leaves (mean P N of 2.6–3.8 μmol CO2 m?2 s?1 leaf area.; mean R Fd of 1.94–2.56). Sun leaves also exhibit higher mean values for the pigment ratio Chl a/b (3.14–3.31) and considerably lower values for the weight ratio total chlorophylls to total carotenoids, (a + b)/(x + c), (4.07–4.25) as compared to shade leaves (Chl a/b 2.62–2.72) and (a + b)/(x + c) of 5.18–5.54. Blue-shade and half-shade leaves have an intermediate position between sun and shade leaves in all investigated parameters including the ratio F v/F o (maximum quantum yield of PS2 photochemistry) and are significantly different from sun and shade leaves but could not be differentiated from each other. The mean values of the Chl fluorescence decrease ratio R Fd of blue-shade and half-shade leaves fit well into the strong linear correlation with the net photosynthetic rates P N of sun and shade leaves, thus unequivocally indicating that the determination of the Chl fluorescence decrease ratio R Fd is a fast and indirect measurement of the photosynthetic activity of leaves. The investigations clearly demonstrate that the photosynthetic capacity and pigment composition of leaves and chloroplasts strongly depend on the amounts and quality of light received by the leaves. 相似文献
10.
《Saudi Journal of Biological Sciences》2022,29(4):2389-2395
The pyrrolidine-2,4-dione derivatives were used to conduct a larvicidal test on Culex quinquefasciatus larvae of the second instar. Mannich base condensation method was used to synthesis the pyrrolidine-2,4-dione derivatives by grindstone method. The reaction conditions were mild, resulting in high yields. An analysis of the synthesized compounds was carried out using FTIR, 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. Synthesized compounds (1a-h) were evaluated for larvicidal activities. Compound 1e (LD50: 26.06 µg/mL), and 1f (LD50: 26.89 µg/mL), and were notably more active against Culex quinquefasciatus than permethrin (LD50: 26.14 µg/mL). The docking studies also demonstrated that 1e, and 1f are potent larvicides with higher binding energy (?12.6 kcal/mol) than the control in the mosquito odorant binding protein (PDB ID: 3OGN). The larvicidal properties of lead molecules have made them important for use as insecticides. 相似文献
11.
Chemical composition of the leaves of Reynoutria japonica Houtt. and soil features in polluted areas
Oimahmad Rahmonov Andrzej Czylok Anna Orczewska Leszek Majgier Tomasz Parusel 《Central European Journal of Biology》2014,9(3):320-330
The study was conducted on six sites that are dominated by Japanese knotweed (Reynoutria japonica) and that vary in the level of industrialization and habitat transformation by humans. The aim of the research was to investigate the chemical-physical features of soil under a closed and dense canopy of R. japonica, the chemical composition of the R. japonica leaves, and to compare the content of certain elements in the soil-plant-soil system. The soil organic carbon (Corg) content varied from 1.38±0.004% to 8.2±0.047% and the maximum in leaves was 49.11±0.090%. The lowest levels of total nitrogen (Ntot) in soil were recorded on the heavily disturbed sites (till 0.227±0.021%). Soil pH varied greatly, ranging from acidic (pH=4.0) to neutral (pH=7.7). Heavy metal content differed significantly among the study sites. At all of the sites, both in the case of soil and plant leaves, Zn was a dominant element and its concentration ranged from 41.5 to 501.2 mg·kg?1 in soils and from 38.6 to 541.7 mg·kg?1 in leaves. Maximum accumulations of P (2103.3±15.3 mg·kg?1) and S (2571.7±17.6 mg·kg?1) were observed on the site that had been influenced by agricultural practices. The results obtained showed that R. japonica is able to accumulate high levels of heavy metals. 相似文献
12.
L. Gratani M. F. Crescente V. D’Amato C. Ricotta A. R. Frattaroli G. Puglielli 《Photosynthetica》2014,52(3):386-396
Global climate change may act as a potent agent of natural selection within species with Mediterranean mountain ecosystems being particularly vulnerable. The aim of this research was to analyze whether the phenotypic plasticity of Sesleria nitida Ten. could be indicative of its future adaptive capability to global warming. Morphological, anatomical, and physiological leaf traits of two populations of S. nitida growing at different altitudes on Mount Terminillo (Italy) were analyzed. The results showed that leaf mass per unit leaf area, leaf tissue density, and total leaf thickness were 19, 3, and 31% higher in leaves from the population growing at 1,895 m a.s.l. (B site) than in leaves from the population growing at 1,100 m a.s.l. (A site), respectively. Net photosynthetic rate (P N) and respiration rate (R D) peaked in June in both A and B leaves [9.4 ± 1.3 μmol(CO2) m?2 s?1 and 2.9 ± 0.9 μmol(CO2) m?2 s?1, respectively] when mean air temperature was 16 ± 2°C. R D/P N was higher in B than in A leaves (0.35 ± 0.07 and 0.21 ± 0.03, respectively, mean of the study period). The mean plasticity index (PI = 0.24, mean of morphological, anatomical, and physiological leaf traits) reflected S. nitida adaptability to the environmental stress conditions at different altitudes on Mount Terminillo. Moreover, the leaf key traits of the two populations can be used to monitor wild populations over a long term in response to global change. 相似文献
13.
《Animal : an international journal of animal bioscience》2015,9(9):1567-1576
The objectives of this study were to investigate the individual variation, repeatability and correlation of methane (CH4) production from dairy cows measured during 2 different years. A total of 21 dairy cows with an average BW of 619±14.2 kg and average milk production of 29.1±6.5 kg/day (mean±s.d.) were used in the 1st year. During the 2nd year, the same cows were used with an average BW of 640±8.0 kg and average milk production of 33.4±6.0 kg/day (mean±s.d.). The cows were housed in a loose housing system fitted with an automatic milking system (AMS). A total mixed ration was fed to the cows ad libitum in both years. In addition, they were offered concentrate in the AMS based on their daily milk yield. The CH4 and CO2 production levels of the cows were analysed using a Gasmet DX-4030. The estimated dry matter intake (EDMI) was 19.8±0.96 and 23.1±0.78 (mean±s.d.), and the energy-corrected milk (ECM) production was 30.8±8.03 and 33.7±5.25 kg/day (mean±s.d.) during the 1st and 2nd year, respectively. The EDMI and ECM had a significant influence (P<0.001) on the CH4 (l/day) yield during both years. The daily CH4 (l/day) production was significantly higher (P<0.05) during the 2nd year compared with the 1st year. The EDMI (described by the ECM) appeared to be the key factor in the variation of CH4 release. A correlation (r=0.54) of CH4 production was observed between the years. The CH4 (l/day) production was strongly correlated (r=0.70) between the 2 years with an adjusted ECM production (30 kg/day). The diurnal variation of CH4 (l/h) production showed significantly lower (P<0.05) emission during the night (0000 to 0800 h). The between-cows variation of CH4 (l/day, l/kg EDMI and l/kg ECM) was lower compared with the within-cow variation for the 1st and 2nd years. The repeatability of CH4 production (l/day) was 0.51 between 2 years. In conclusion, a higher EDMI (kg/day) followed by a higher ECM (kg/day) showed a higher CH4 production (l/day) in the 2nd year. The variations of CH4 (l/day) among the cows were lower than the within-cow variations. The CH4 (l/day) production was highly repeatable and, with an adjusted ECM production, was correlated between the years. 相似文献
14.
Nonparasitized second-instar larvae of Trichoplusia ni were twice as susceptible (at the LD50 level) to the singly enveloped T. ni nuclear polyhedrosis virus as those parasitized by Hyposoter exiguae (Hymenoptera: Ichneumonidae). The LD50 values for nonparasitized and parasitized larvae were 1.58 × 103 and 3.16 × 103 polyhedra/ml of diet, respectively. The LD95 value for parasitized larvae was approximateely 5 times higher than that for nonparasitized larvae. The slopes (b values) were 1.2 for parasitized larvae and 1.7 for nonparasitized larvae. The LT50 values for parasitized larvae also were significantly longer than those for nonparasitized larvae. No significant difference was found between the food consumption of parasitized and nonparasitized T. ni larvae. 相似文献
15.
Osariyekemwen O. Uyi Bridget I. Uwagiahanor Afure J. Ejomah 《Arthropod-Plant Interactions》2017,11(4):603-611
Increasing evidence suggests that the responses of insect herbivores to environment-mediated changes in the phenotypic and phytochemical traits of their host plants are more complex than previously thought. Here, we examined the effects of habitat conditions (shaded versus full-sun habitats) on plant traits and leaf characteristics of the invasive alien plant, Chromolaena odorata (L.) (Asteraceae). We also determined neonate larval preference of the specialist herbivore, Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Erebidae) (a biological control agent) for shaded versus full-sun leaves. The study further evaluated the performance of the moth on C. odorata leaves obtained from both shaded and full-sun habitats. Leaves of C. odorata plants growing in the shaded habitat had higher water and nitrogen contents compared with full-sun leaves. Plants growing in shade had longer leaves but full-sun plants were taller and had greater aboveground biomass compared with shaded plants. Although neonate larvae of P. pseudoinsulata preferred to feed on full-sun foliage, development was faster when reared on shaded foliage. However, survival, pupal mass, growth rate, and Maw’s host suitability index of the moth did not significantly differ between full-sun and shaded foliage. Our inability to demonstrate significant differences in key insect performance metrics in P. pseudoinsulata between shaded and full-sun foliage, despite neonate larval preference for one of the foliage types, suggests that neither of the foliage types can be considered a superior host, and reiterate the fact that relationships between host plant quality (modulated by light intensity) and phytophagous insect performance are not simple. 相似文献
16.
Shin-Ichiro Katahata Masaaki Naramoto Yoshitaka Kakubari Yuzuru Mukai 《Trees - Structure and Function》2007,21(6):619-629
Seasonal changes in photosynthetic capacity, leaf nitrogen (N) content, leaf chlorophyll (Chl) content and leaf N allocation
patterns in leaves of different ages in the evergreen understory shrub, Daphniphyllum
humile Maxim, growing at a forest border and an understory site were studied. In current-year leaves at the understory site, the
N and Rubisco contents increased from spring to autumn although their light-saturated photosynthetic rate at 22°C (P
max22) remained stable, indicating that their mesophyll conductance rates declined as they completed their development and/or that
they invested increasing amounts of their resources in photosynthetic enzymes during this period. In contrast, seasonal changes
in P
max22 in current-year leaves at the forest border site were correlated with changes in Rubisco content. In 1-year old leaves at
the understory site, P
max22 and contents of Chl, leaf N, and Rubisco remained stable from spring to autumn, while these parameters decreased in 1-year-old
forest border leaves, indicating that N may have been remobilized from shaded 1-year-old leaves to sunlit current-year leaves.
When leaves senesced at the forest border site the Rubisco content decreased more rapidly than that of light-harvesting proteins
such as LHCII, suggesting that N remobilization from Rubisco may be more efficient, possibly because Rubisco has greater N
costs and is soluble, whereas the light-harvesting proteins are membrane components. 相似文献
17.
In leaves of the mangrove species Avicennia germinans (L.) L. grown in salinities from 0 to 40 ‰, fluorescence, gas exchange, and δ13C analyses were done. Predawn values of Fv/Fm were about 0.75 in all the treatments suggesting that leaves did not suffer chronic photoinhibition. Conversely, midday Fv/Fm values decreased to about 0.55-0.60 which indicated strong down-regulation of photosynthesis in all treatments. Maximum photosynthetic rate (P max) was 14.58 ± 0.22 µmol m-2 s-1 at 0 ‰ it decreased by 21 and 37 % in plants at salinities of 10 and 40 ‰, respectively. Stomatal conductance (g s) was profoundly responsive in comparison to P max which resulted in a high water use efficiency. This was further confirmed by δ13C values, which increased with salinity. From day 3, after salt was removed from the soil solution, P max and g s increased up to 13 and 30 %, respectively. However, the values were still considerably lower than those measured in plants grown without salt addition. 相似文献
18.
The thermotolerance of the sun-exposed peel and the shaded peel of ‘Fuji’ apple (Malus domestica Borkh.) fruit was evaluated by measuring pigments, chlorophyll a fluorescence transients and O2 evolution or uptake after exposure to 25, 35, 40, 42, 44, 46 or 48 °C for 30 min in the dark. A major effect of heat stress at 46–48 °C on the chlorophyll a fluorescence transients was the appearance of a very clear K step at 200–300 μs for both peel types. The K step was slightly more pronounced in the sun-exposed peel than in the shaded peel, suggesting that the resistance of oxygen-evolving complex to heat stress is slightly lower in the sun-exposed peel than in the shaded peel. Minimal fluorescence (FO), relative to the value at 25 °C, increased to a greater extent in the shaded peel than in the sun-exposed peel after exposure to 46–48 °C, but the temperature dependencies of FO changes were similar for both peel types. Maximum quantum yield of PSII (FV/FM) decreased to a similar extent in the sun-exposed peel and the shaded peel as temperature rose from 25 to 44 °C, but the sun-exposed peel reached slightly lower values at 46–48 °C. Correspondingly, gross O2 evolution rate, relative to that at 25 °C, was also slightly lower in the sun-exposed peel than in the shaded peel at 46–48 °C. In response to heat stress, the ratio of QA-reducing reaction centers (RCs) to total RCs and the ratio of QB-reducing RCs to QA-reducing RCs decreased, but both of them decreased to lower values in the sun-exposed peel than in the shaded peel at 46–48 °C, indicating that the capacity of electron transfer between P680+ and QB via QA was damaged to a greater extent in the sun-exposed peel than in the shaded peel. At each given temperature, dark respiration was similar between the two peel types. Overall, it appears that the exposure to higher surface temperature under high light does not make the sun-exposed peel more tolerant of heat stress than the shaded peel of apple fruit. 相似文献
19.
Thick sun leaves have a larger construction cost per unit leaf area than thin shade leaves. To re-evaluate the adaptive roles
of sun and shade leaves, we compared the photosynthetic benefits relative to the construction cost of the leaves. We drew
photosynthetically active radiation (PAR)-response curves using the leaf-mass-based photosynthetic rate to reflect the cost.
The dark respiration rates of the sun and shade leaves of mulberry (Morus bombycis Koidzumi) seedlings did not differ significantly. At irradiances below 250 μmol m−2 s−1, the shade leaves tended to have a significantly larger net photosynthetic rate (P
N) than the sun leaves. At irradiances above 250 μmol m−2 s−1, the P
N did not differ significantly. The curves indicate that plants with thin shade leaves have a larger daily CO2 assimilation rate per construction cost than those with thick sun leaves, even in an open habitat. These results are consistently
explained by a simple model of PAR extinction in a leaf. We must target factors other than the effective assimilation when
we consider the adaptive roles of thick sun leaves. 相似文献
20.
Morphological, anatomical and physiological summer and winter leaf traits of Cistus incanus subsp. incanus, C. salvifolius and C. monspeliensis growing at the Botanical garden of Rome were analyzed. With regard to differences between summer and winter leaves of the considered species, leaf thickness (L) was 21% higher in summer than in winter leaves (mean of the considered species) and this increase was mostly the result of the increased palisade parenchyma thickness over the spongy parenchyma one (24 and 16% higher in summer than in winter leaves, respectively). Leaf mass area (LMA) and leaf tissue density (LTD) were 38% and 17% higher in summer than in winter leaves, respectively (mean of the considered species). The photosynthetic rate (PN), stomatal conductance (gs) and chlorophyll content (Chl) of summer leaves were 54%, 17% and 14% lower, respectively, than in winter leaves. C. monspeliensis summer leaves had the highest LMA, LTD, adaxial cuticle thickness (14.6 ± 1.8 mg cm−2, 1091 ± 94 mg cm−3, and 5.8 ± 1.7 μm, respectively) and the lowest mesophyll intercellular spaces (fias 38 ± 3%). Moreover, C. monspeliensis had the highest PN in summer (2.6 ± 0.1 μmol m−2 s−1) and C. incanus the highest PN and WUE (84% and 59% higher than the other species) in the favorable period, associated to a higher fias (42 ± 2%). C. salvifolius had the highest PN (54% higher than the other species) in winter. The plasticity index could allow a better interpretation of the habitat preference of the considered species. The physiological plasticity (PIp = 0.39, mean value of the considered species) was higher than the morphological (PIm = 0.22, mean value) and anatomical (PIa = 0.13, mean value) plasticity. Moreover, among the considered species, C. salvifolius and C. incanus are characterized by a larger PIa (0.14, mean value) which seems to be correlated with their wider ecological distribution and the more favorable conditions of the environments where they naturally occur. The highest PIm (0.29) of C. monspeliensis indicates that it can play a high adaptive role in highly stressed environments, like fire degraded Mediterranean areas in which it occurs. 相似文献