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1.
Pinus sylvestriformis is an important species as an indicator of global climate changes in Changbai Mountain, China. The water use efficiency (WUE) of this species (11-year old) was studied on response to elevated CO2 concentration at 500±100 μL·L−1 by directly injecting CO2 into the canopy under natural condition in 1998–1999. The results showed that the elevated CO2 concentration reduced averagely stomatal opening, stomatal conductance and stomatal density to 78%, 80% and 87% respectively, as compared to normal ambient. The elevated CO2 reduced the transpiration and enhances the water use efficiency (WUE) of plant. The project was supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai  相似文献   

2.
Plant growth, biomass allocation, carbon isotope composition (δ13C), and water use efficiency (WUE) of 31 cultivars of apple (Malus domestica Borkh.) grown under two water regimes were measured. Drought-stressed plants showed significant declines in tree height, trunk diameter, biomass production, and total leaf area, the extent to which depended upon cultivar. Also, gas exchange rates, instantaneous and long-term efficiencies (WUEI and WUEL, respectively), and values for δ13C differed among cultivars and watering regimes. Variations in WUEI were mainly due to changes in stomatal conductance (g s) under drought condition. ‘Qinguan’ and ‘Golden Delicious’ had greater trunk diameter, tree height, and had higher biomass production and WUEL under drought stress, implying that they are more suitable for arid and semi-arid regions. Moreover, WUEL was significantly and positively correlated with δ13C under two watering regimes, which suggests a potential for evaluating water use efficiency of Malus by measuring carbon isotope composition.  相似文献   

3.
目的]探究抑制剂对大叶黄杨生长的抑制作用以及对其叶片形态和光合作用的影响,为灌木绿篱的化学修剪提供技术指导。[方法]在北京林业大学林场苗圃采用3种生长抑制剂(多效唑(PP_(333))、三碘苯甲酸(TIBA)以及脱落酸(ABA))对密植成绿篱状的1年生大叶黄杨扦插苗进行叶面喷施,对其生长、叶片形态及光合作用等指标进行测定。[结果]3种抑制剂均有矮化植株、抑制新梢生长的作用,矮化效果最佳、抑制作用最强的为PP_(333),且高浓度PP_(333)对于高生长的抑制作用持效性较长。叶宽、叶厚以及叶面积在短期PP_(333)处理下高于对照。PP_(333)能提高大叶黄杨净光合速率,主要通过增加叶厚、气孔导度、叶肉导度及叶绿素含量来实现,并且PP_(333)使蒸腾速率提高的同时降低了水分利用效率。TIBA有显著减小叶长、叶宽的作用,但能使叶厚增加,且随浓度的增加作用效果增强,主要通过减小叶面积,降低叶肉导度、气孔导度、胞间CO_2浓度及叶绿素含量来降低净光合速率。ABA能增加叶面积(10 mg·L~(-1)处理除外)、叶长以及减小叶片厚度,通过抑制气孔导度、叶肉导度、叶绿素含量降低净光合速率。TI-BA及ABA均通过降低蒸腾速率,使水分利用效率提高。[结论]3种抑制剂均有矮化植株、抑制新梢生长的作用,并且影响叶片发育,进而影响叶片光合作用,且800 mg·L~(-1)的多效唑对大叶黄杨具有较好的正向作用。  相似文献   

4.
In 2000, one-year-old seedlings of pyrenean oak (Quercus pyrenaica Willd.) and sessile oak (Quercus petraea [Matt.] Liebl) were planted in a thinned and an unthinned plot in a pinewood (Pinus sylvestris), and in a nearby clearing. In summer 2002 and 2003, water relations and gas exchange parameters were measured to address the impact of drought on the seedlings. Chlorophyll a fluorescence was also measured to explore leaf photochemistry and a possible non-stomatal limitation to photosynthesis (A). Reduction in stomatal conductance (g) in response to the decrease of predawn water potential (Ψpd) resulted the main cause affecting net carbon uptake. Water potential at midday (Ψmd) was similar in both species but Quercus petraea was more sensitive to soil water deployment occurred along summer, showing slightly lower Ψpd because worse recover of water potential during night. Rate of photosynthesis was higher in Q.␣pyrenaica probably in relation to its greater leaf mass per area (LMA) and nitrogen content per leaf area (Na). Mortality was highest in the clearing and lowest in the thinned pinewood. Throughout the summer, soil moisture was higher in the thinned area, possibly because of the reduction in tree transpiring surface and interception of rainfall. Accordingly, Ψpd of both species was higher in the thinned site.  相似文献   

5.
The water relation and leaf gas exchange of saxoul (Haloxylon Ammodendron Bge, a C4 shrub) seedlings were studied under water stress in 2001. Saxoul seedlings maintained high transpiration when the soil moisture was above 11%. The seedlings were able to take up water from soil with above 6 % soil water content, which was the threshold level of soil moisture for seedlings. The relationship between transpiration and potential evaporation was linear for well-watered seedlings. The decrease of soil water availability led to different degrees of down-regulation of stomatal conductance, leaf transpiration and net CO2 assimilation rate. The stomata played a relatively small part in determining the net CO2 assimilation rate for the same seedling. The relationship between net CO2 assimilation rate and transpiration was linear diurnally, and reduction scale of leaf transpiration was much bigger than that of net CO2 assimilation rate by waters tress treatments, therefore intrinsic water-use-efficiency increased. High evaporative demand increased the leaf transpiration but inhibited net CO2 assimilation rate.Because of the effect of VPD on transpiration in this region, the transpiration of well-watered and mild water stress seedlings becomes responsive to change in stomatal conductance over a wider range.  相似文献   

6.
Foliar carbon isotope composition (δ 13C), total dry biomass, and long-term water use efficiency (WUEL) of 12 Populus deltoids clones were studied under water stress in a greenhouse. Total dry biomass of clones decreased greatly, while δ 13C increased. Single-element variance analysis in the same water treatment indicated that WUEL difference among clones was significant. Clones J2, J6, J7, J8, and J9 were excellent with high WUEL. Extremely significant δ 13C differences among water treatments and clones were revealed by two-element variance analysis. Water proved to be the primary factor affecting δ 13C under water stress. It showed that there was a good positive correlation between δ 13C and WUEL in the same water treatment, and that a high WUEL always coincided with a high δ 13C. δ 13C might be a reliable indirect index to estimate WUEL among P. deltoids clones. Translated from Scientia Silvae Sinicae, 2005, 41(1) (in Chinese)  相似文献   

7.
Natural abundance of 15N was sampled in young and mature leaves, branches, stem, and coarse roots of trees in a cacao (Theobroma cacao) plantation shaded by legume tree Inga edulis and scattered non-legumes, in a cacao plantation with mixed-species shade (legume Gliricidia sepium and several non-legumes), and in a tree hedgerow bordering the plantations in Guácimo, in the humid Caribbean lowlands of Costa Rica. The deviation of the sample 15N proportion from that of atmosphere (δ15N) was similar in non-legumes Cordia alliodora, Posoqueria latifolia, Rollinia pittieri, and T. cacao. Deep-rooted Hieronyma alchorneoides had lower δ15N than other non-N2-fixers, which probably reflected uptake from a partially different soil N pool. Gliricidia sepium had low δ15N. Inga edulis had high δ15N in leaves and branches but low in stem and coarse roots. The percentage of N fixed from atmosphere out of total tree N (%Nf) in G. sepium varied 56–74%; N2 fixation was more active in July (the rainiest season) than in March (the relatively dry season). The variation of δ15N between organs in I. edulis was probably associated to 15N fractionation in leaves. Stem and coarse root δ15N was assumed to reflect the actual ratio of N2 fixation to soil N uptake; stem-based estimates of %Nf in I. edulis were 48–63%. Theobroma cacao below I. edulis had lower δ15N than T. cacao below mixed-species shade, which may indicate direct N transfer from I. edulis to T. cacao but results so far were inconclusive. Further research should address the 15N fractionation in the studied species for improving the accuracy of the N transfer estimates. The δ15N appeared to vary according to ecophysiological characteristics of the trees.  相似文献   

8.
One-year-old seedlings of Amur maple (Acer ginnala Maxim), Ussurian pear (Pyrus ussuriensis Maxim) and David peach (Prunus davidiana Carr) were planted in pots in greenhouse and treated with four different soil moisture contents (75.0%,61.1%, 46.4% and 35.4%). The results showed that net photosynthesis rate (NPR), transpiration rate (TR) and stomatal conductance (Sc) of seedlings of the three species decreased with the decease of soil moisture content, and Amur maple seedlings had the greatest change in those physiological indices, followed by Ussurian pear, David peach. Amur maple and Ussurian pear seedlings also presented a decrease tendency in water use efficiency (WUE) under lower soil moisture content, whereas this was reversed for David peach. Under water stress the biomass allocation to seedling root had a significant increase for all the experimental species. As to root/shoot ratio, Amur maple seedlings had the biggest increase, while David peach had the smaliest increase. The leaf plasticity of Amur maple seedlings was greater, the leaf size and total leaf area decreased significantly as the stress was intensified. No significant change of leaf size and total leaf area was found in seedlings of Ussurian pear and David peach. It was concluded that Amur maple was more tolerant to soil moisture stress in comparison with David peach and Ussurian pear.  相似文献   

9.
Variations in biomass productivity, plant water-use efficiency (WUEp), and carbon isotope composition (δ13C) were investigated among 10 Malus rootstocks. In the semi-controlled environmental of a greenhouse, plants were watered to either 75% or 50% of field capacity. For each treatment, significant differences were found in dry matter accumulation and allocation, δ13C, and WUEp. Relative growth rate (RGR) was correlated with WUEp but not with allocation pattern. Variations in whole-plant transpiration were a result of fluctuations in the rate of transpiration per unit leaf area rather than from differences in leaf area or root weight per plant. Values for transpiration per unit leaf area or root weight were lower when the proportion of either leaf area or root weight per unit plant weight was larger. Rootstock differences in δ13C were related to changes in stomatal conductance rather than in net photosynthesis. Finally, δ13C was significantly correlated with WUEp and rootstock rankings based on both of those parameters were maintained regardless of watering treatment.  相似文献   

10.
Seasonal changes in carbon isotope discrimination (Δ) and gas exchange traits were assessed in four Populus×euramericana clones differing in growth potential. Measurements were made during the second year after establishment in the field under two watering regimes, which were defined by the time-span between flood irrigations, hence resulting in different dry-down cycles: high irrigation (conservative schedule currently applied in the Ebro Valley, Spain) and low irrigation (equivalent to about a one-fourth reduction in water inputs). Net CO2 assimilation rate (A), stomatal conductance (gs), intrinsic water-use efficiency (A/gs) and other related photosynthetic traits (leaf nitrogen concentration, leaf greenness and leaf mass per area) were measured prior to watering, and Δ was analysed in water-soluble leaf extracts (Δs) and bulk leaves (Δl). Stem growth was monitored over 3 years starting at the year of establishment (1998). Data were subjected to a repeated measures ANOVA over time for a randomised block split-plot design across watering regimes. Significant differences between watering regimes were detected using a long-term estimate of photosynthetic performance such as Δl, in agreement with changes in soil water status and evapotranspirative demand. However, the lack of significant genotype×watering regime interactions for gas exchange traits and Δs suggested that water shortage imposed by low irrigation was not sufficient to reveal physiological adaptations to drought. In this regard, the reduction in water inputs brought about by low irrigation did not reduce tree growth for any of the clones, suggesting that the current irrigation scheme employed in the region is superfluous to the water consumption needs of poplars. Genotypic variation was detected in gas exchange traits, Δs, Δl and stem growth under both watering treatments. Significant correlations with stem volume for Δs (r = −0.60, p<0.05) and A (r = + 0.61, p<0.05) suggested that growth was improved by higher water-use efficiency (the ratio of carbon fixed to water lost, as inferred by Δs) due to variation in A rather than in gs. This observation corroborated the expectation derived from current theories that a lower Δ is related to higher stem volume, as a result of changes in net CO2 assimilation rates.  相似文献   

11.
To elucidate the differences in the leaf water relations of Pinus densiflora Sieb. et Zucc. growing in different soil moisture conditions, we examined the pressure-volume curve and the diurnal changes in the stomatal conductance, the transpiration rate, and the leaf water potential. The leaf water relations were compared using field-grown 40-year-old pine trees growing on the upper and lower parts of a slope. We also compared the leaf water relations of potted 4-year-old saplings growing at pF 4.2 and pF 1.8 soil moisture levels for almost 1 year. The values of the ratio of symplasmic water at turgor loss point to symplasmic water at saturated point (Vp/Vo) and bulk modulus of elasticity () of both the adult trees on the upper part of the slope and the potted saplings growing on pF 4.2 soil moisture were higher than those values of both the adult trees on the lower part of the slope and the potted saplings growing on pF 1.8 soil moisture, respectively. The field-grown adult tree and the potted saplings growing under long-term water stress tended to reduce their stomatal conductance in response to the acute soil drying. It is suggested that P. densiflora growing under long-term water stress rapidly closed its stomata in response to soil drying and avoided losing water, and could also rapidly absorb water with reducing water loss because of the decrease in the leaf pressure potential derived from the high values.  相似文献   

12.
Four different kinds of water treatment were applied to examine the photosynthetic characteristics of baldcypress (Taxodium distichum) seedlings in the hydro-fluctuation belt of the Three Gorges Reservoir area. The aim was to shed light on the physio-ecological adaptation of this species to changing water levels for revegetation purposes. The water treatments were normal growth water condition (CK), light drought water stress (T1), growth under soil water saturation (T2) and growth with soil submersion (T3). T3 had the lowest content of photosynthetic pigment; T1 and T2 did not differ from CK in the content of chlorophyll and carotenoid. The ratio of chlorophyll a to b in the four groups ranged from 2.04 to 2.69 and the ratio of chlorophyll to carotenoid from 3.08 to 4.51. In group T1, the seedling of baldcypres had lower apparent light use efficiency, lower apparent CO2 use efficiency and a lower net photosynthetic rate, with the net photosynthetic rate 24.9% lower than that of group CK. However, T2 and T3 did not differ from CK in apparent light use efficiency, apparent CO2 use efficiency and net photosynthetic rate. Water use efficiency of the four treatments consistently increased as treatment was prolonged; the average water use efficiency of T3 was the lowest while that of CK was the highest. Correlation analysis showed that the net photosynthetic rate of baldcypress seedlings was positively related to transpiration rate, stomatal conductance, water use efficiency, apparent light use efficiency and apparent CO2 use efficiency, but highly negatively related to the ratio of chlorophyll a to b. Net photosynthetic rate was not significantly related to the contents of chlorophyll and carotenoid, the ratio of chlorophyll to carotenoid, relative air humidity and intercellular CO2 concentration. The transpiration rate was positively correlated with stomatal conductance and negatively related to water use efficiency. The results showed that different water treatments could effectively influence the baldcypress seedlings’ content of photosynthetic pigment, leaf gas exchange and apparent resources use efficiency. The results verified that the species T. distichum takes on the features of a water-tolerant and hydrophilic plant, which can be considered as one of the species for the building of a forest protection system for the hydro-fluctuation belt in the Three Gorges Reservoir area. Baldcypress should not be planted in drought-stricken soils. __________ Translated from Acta Ecologica Sinica, 2005, 25(8) [译自:生态学报, 2005, 25(8)]  相似文献   

13.
Four-year-oldPinus sylvestriformis were exposed for four growing seasons in open top chambers to ambient CO2 concentration (approx. 350 μmol·mol−1) and high CO2 concentrations (500 and 700 μmol·mol−1) at Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences at Antu Town, Jilin Province, China (42°N, 128°E). Stomatal response to elevated CO2 concentrations was examined by stomatal conductance (g s), ratio of intercellular to ambient CO2 concentration (c i/c a) and stomatal number. Reciprocal transfer experiments of stomatal conductance showed that stomatal conductance in high-[CO2]-grown plants increased in comparison with ambient-[CO2]-grown plants when measured at their respective growth CO2 concentration and at the same measurement CO2 concentration (except a reduction in 700 μmol·mol−1 CO2. grown plants compared with plants on unchambered field when measured at growth CO2 concentration and 350 μmol·mol−1CO2). High-[CO2]-grown plants exhibited lowerc i/c a ratios than ambient-[CO2]-grown plants when measured at their respective growth CO2 concentration. However,c i/c a ratios increased for plants grown in high CO2 concentrations compared with control plants when measured at the same CO2 concentration. There was no significant difference in stomatal number per unit long needle between elevated and ambient CO2. However, elevated CO2 concentrations reduced the total stomatal number of whole needle by the decline of stomatal line and changed the allocation pattern of stomata between upper and lower surface of needle. Foundation Item: This research was supported by National Basic Research Program of China (2002CB412502), Project of Key program of the National Natural Science Foundation of China (90411020) and National Natural Science Foundation of China (30400051). Biography: ZHOU Yu-mei (1973-), female, Ph. Doctor, assistant research fellow, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan  相似文献   

14.
In order to offer a scientific basis for cultivation and management of forests, effects of light radiation intensity on photosynthetic characteristics and water use efficiency of Platycladus orientalis and Pinus tabulaeformis were studied under different soil moisture contents. By adopting artificial control methods to soil moisture, and under simulated photosynthetic radiation (SPR), the net photosynthetic rate (P N), transpiration rate (T r), water use efficiency (WUE) and intercellular CO2 concentration (C i) of Platycladus orientalis and Pinus tabulaeformis in the semi-arid region of the Loess Plateau, were studied. Results are as follows: within the photon range of 0–2,200 μmol/(m2·s), P N, T r and WUE were enhanced with an increase in SPR in both species. P N and WUE of Platycladus orientalis and Pinus tabulaeformis, however, declined with continued increase in SPR. P N, T r, WUE and light saturation point (LSP) of Platycladus orientalis were higher than those of Pinus tabulaeformis, while light compensation point (LCP) of Platycladus orientalis was lower than that of Pinus tabulaeformis at the same soil moisture content. The efficiency of light energy utilization of Platycladus orientalis was higher than that of Pinus tabulaeformis; P N, T r and C i of Platycladus orientalis and Pinus tabulaeformis were enhanced by increasing soil moisture content, whereas WUE declined. At soil moistures of 7.90%, 13.00% and 19.99%, LSP of Platycladus orientalis was 1,275, 1,450 and 1,675 μmol/(m2·s) respectively, and LCP was 42, 25 and 13 μmol/(m2·s) respectively, with corresponding maximal net CO2 photosynthetic rates (P max) of 3.04, 4.06 and 5.53 μmol/(m2·s). At soil moistures of 7.83%, 13.04% and 20.15%, the LSP of Pinus tabulaeformis was 1,100, 1,325 and 1,500 μmol/(m2·s) respectively, and LCP was 60, 30 and 23 μmol/(m2·s), with P max of 1.08, 3.35 and 4.36 μmol/(m2·s) respectively. __________ Translated from Science of Soil and Water Conservation, 2006, 4(3): 108–113 [译自: 中国水土保持科学]  相似文献   

15.
The loss of foliage through pruning of live branches may reduce tree growth or it may be compensated by photosynthetic up-regulation of the remaining crown. Here, the changes in light-saturated photosynthesis following pruning to remove 50% of green crown length were examined in 4-year-old Eucalyptus pilularis Sm. and Eucalyptus cloeziana F. Muell. trees. The objectives of the study were to: (1) compare leaf-level physiological (light-saturated photosynthesis (Amax), stomatal conductance (g), transpiration (T), dark respiration (Rd), quantum yield (Φ), light compensation point (Γ), water-use efficiency (WUE), nitrogen-use efficiency (NUE)) traits in species with contrasting crown dynamics and structure, (2) examine the effect of crown position on these traits, and (3) examine the effect of pruning on Amax, g, T, WUE, NUE, leaf N and P concentrations and specific leaf area (SLA). Prior to pruning there were no differences in Rd, Γ and Φ between E. pilularis and E. cloeziana but differences in Amax, T, g, leaf N, leaf P, WUE, NUE and SLA. Whereas the rate of physiological processes (Amax, T, and g) and leaf N and P concentrations increased with crown height, Rd, Γ, Φ and SLA declined along this vertical gradient, except in the upper crown of E. cloeziana where Amax, T and g were not different to the lower crown. No up-regulation of photosynthesis or changes in leaf physiology occurred between 6 and 13 months after pruning in either species. The results provide an important basis for modelling pruning effects in process-based tree growth models.  相似文献   

16.
Due to the expected increases of number and intensity of summer droughts in Central Europe the identification of drought tolerant ecotypes becomes more important in future forestry. A common garden experiment with seedlings of Fagus sylvatica provenances from the center (Germany) and eastern margin (Poland) of the species’ distribution range was conducted. Responses of morphological, physiological, chemical and growth parameters to three drought treatments were analyzed. Relative growth rates of the marginal provenance were lower as compared to the central provenance. The marginal seedlings showed a tendency to higher total biomasses because of higher seed masses. In both provenances drought decreased biomass production and root/shoot ratio which was lower in the central provenance. A lower specific root area of the marginal provenance indicated a better adaptation to low xylem water potentials. Under moderate drought, lower leaf δ13C signatures may indicate lower stomatal limitation (or a reduced rate of CO2 assimilation) in the marginal provenance. We conclude that marginal beech provenances may exhibit a better drought adaptation.  相似文献   

17.
This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N2 fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the 15N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha–1 yr–1) originated from N2 fixation. Grass production averaged 13 Mg ha–1 yr–1 and N export in cut grass was 195 kg [N] ha–1 yr–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha–1 yr–1. Carbon sequestration averaged 1.9 Mg [C] ha–1 yr–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha–1 yr–1, corresponding to 30% of N2 fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha–1 yr–1) and litter decomposition (40 kg [N] ha–1 yr–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

18.
The biomass production of both indigenous and introduced plant species in tropical fallow systems depends on the degree to which these species can acclimate to the light and water environments. Results for light spectral composition monitoring within the canopy of enriched fallows and for the leaf stomatal conductance of fast-growing leguminous trees and indigenous fallow species are presented. All measurements were made in a smallholder farm in Igarapé-Açu, northeastern Pará State, Brazil. Light spectral composition (330 to 1100 nm) was monitored at two heights (ground level and 1 m) in a six-year-old natural fallow, 1.5-year-old natural fallow, and 1.5-year-old fallows enriched with Acacia angustissima, Acacia mangium, Clitoria racemosa, Inga edulis, Sclerolobium paniculatum, and a mixture of these trees. Light-quality parameters including photosynthetically active radiation, phytochrome active radiation, and blue active radiation changed most drastically in the stands enriched with A. mangium. Stomatal conductance was higher for A. mangium than the other trees and four common indigenous fallow vegetation species (Phenakospermum guyannense, Davilla rugosa, Lacistema pubescens, and Myrcia bracteata). Results suggest that the enrichment of fallows with A. mangium may promote changes in light and water vapor exchange regimes, with potential effects on species diversity in fallows.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

19.
The rough extent of leaf surface may be described by protruding of waxes which like as wart and of stomatal aperture and of width of the cuticular ledge around guard cells. Because the morphology of the leaf surface has obviously similar itself, so one can use the theory of the fractal dimension to deal with the problems of leaf surface rough. The paper studied the rough extent and the result showed: with the leaf growing up, the waxes accumulate more and more, the leaf surface is more rough and the dimension is larger. The dimension D w p which indicates the rough extent of warts protruding is about 2.10–2.20 on the above epidermis; On the beneath epidermis the dimension D s p of stomatal opening protruding is about 2.00–2.24; Maximum widthL of cuticular ledge is about 1.0–7.4μm. The project supported by Natural Science Foundation of China  相似文献   

20.
The light response curve and the intercellular CO2 concentration response curve of CO2 assimilation rate were investigated together with the light conditions at the four different heights within the beech crown from 1995 to 1997 on Mt. Fuji in Japan. On the seasonal fluctuation, the CO2 assimilation rate at light saturated condition increased rapidly in May, and attained to the maximum between the end of June and July, thereafter, slightly decreased until the middle of August and rapidly decreased in September and October. The daily sum of photosynthetic photon flux density attenuated with deeping within the crown, and particularly, the relative value on 2nd position dropped to only 30%. TheA max decreased from 10 to 5μmol m−2 s−1, approximately, with deeping within the crown. The light saturation point, quantum yield, light compensation point and dark respiration rate also varied with deeping. These results suggest that the photosynthetic properties vary gradually from sun to shade leaves along the light attenuation within a beech crown. At light saturated condition, the stomatal conductance and mesophyll conductance were strongly correlated withA max among the four different heights (r > 0.96, respectively). TheC i/C a ratio was around 0.8, and there were no remarkable differences among the four different heights. These results suggest that the vertical gradient ofA max depends on the variation of mesophyll conductance. The stomatal conductance may be also one of the major factor in the vertical gradient ofA max. However the intercellular CO2 concentration doesn’t influence the vertical gradient ofA max within the crown. This work is supported by the Sasagawa Scientific Research Grant from The Japan Science Society and Grant-in-Aid for Scientific Research (C).  相似文献   

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