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1.
We investigated the effects of an ambient dose of ultraviolet-B (UV-B) radiation on chamber-grown Pseudotsuga menziesii var. glauca (Beissn.) Franco (Douglas-fir) seedlings, to determine if the presence of UV-B radiation in the growth light regime induces tolerance to environmental stresses such as high light and drought. Douglas-fir seedlings were grown without UV-B radiation or with 6 kJ m-2 day-1 of biologically effective UV-B, which is ambient for the intermountain regions of Idaho. Non-stressed seedlings grown with UV-B radiation had 35% lower seedling dry mass, 36% higher concentrations of UV-B absorbing compounds per unit leaf area, 30% lower stomatal frequencies, 25% lower light-saturated photochemical efficiencies of Photosystem II and 45% lower light-saturated stomatal conductance than non-stressed seedlings grown without UV-B radiation. After 4 days of high-light stress, seedlings grown with UV-B radiation had 32% higher light-saturated carbon assimilation rates (A(CO2)) than seedlings grown without UV-B radiation. After water was withheld from the seedlings for up to 15 days, seedlings grown with UV-B radiation had 50% higher A(CO2) and 40% higher seedling water potentials than seedlings grown without UV-B radiation. The results support the hypothesis that UV-B radiation can act as an environmental signal to induce tolerance to high-light and drought stress in Douglas-fir seedlings. Possible mechanisms for the enhanced stress tolerance are discussed. 相似文献
2.
We investigated sex-related morphological and physiological responses to enhanced UV-B radiation in the dioecious species Populus cathayana Rehd. Cuttings were subjected to two UV-B radiation regimes: ambient (4.5 kJ m?2 day?1) and enhanced (12.5 kJ m?2 day?1) biologically effective UV-B radiation for one growing season. Enhanced UV-B radiation was found to significantly decrease the shoot height and basal diameter and to reduce the leaf area, dry matter accumulation, net photosynthesis rate (P(n)), chlorophyll a/b ratio (Chl a/b) and anthocyanin content. Enhanced UV-B radiation also increased chlorophyll pigment, leaf nitrogen, malondialdehyde and abscisic acid (ABA) content, superoxide dismutase and peroxidase activities and UV-B-absorbing compounds. No significant effects of enhanced UV-B radiation were found on biomass allocation, gas exchange (except for P(n)), photochemical efficiency of photosystem II or water use efficiency. Moreover, different sensitivity to enhanced UV-B radiation between males and females was detected. Under enhanced UV-B radiation, males exhibited significantly higher basal diameter and leaf nitrogen, and lower Chl a/b, ABA content, UV-B-absorbing compounds, as well as less decrement of leaf area and dry matter accumulation than did females. However, no significant sexual differences in these traits were found under ambient UV-B radiation. Our results suggest that males may possess a greater UV-B resistance than do females, with males having a more efficient antioxidant system and higher anthocyanin content to alleviate UV-B penetration stress than females. 相似文献
3.
We compared the growth and physiological responses of cuttings of Populus kangdingensis C. Wang et Tung and P. cathayana Rehder originating from altitudes of 3500 m and 1500 m, respectively, when exposed to three ultraviolet-B (UV-B) radiation regimes: zero UV-B, ambient (4.5 kJ m(-2) day(-1)) and twice-ambient (9 kJ m(-2) day(-1)) biologically effective UV-B radiation for one growing season, to determine if Populus trees that are adapted to contrasting UV-B habitats exhibit different tolerances to enhanced UV-B radiation. Compared with cuttings grown without UV-B radiation, twice-ambient UV-B radiation significantly decreased total biomass, total leaf area and internode length in both species, whereas root/shoot ratio, leaf number, amount of photosynthetic pigments and ascorbate peroxidase activity were unaffected. Differences in responses were also observed between the study species. Cutting height increment, total biomass, total leaf area, free proline concentration and membrane damage assessed by electrolyte leakage were significantly more affected by the twice-ambient UV-B radiation in P. cathayana than in P. kangdingensis. However, specific leaf mass, amount of UV-B absorbing compounds and superoxide dismutase and guaiacol peroxidase activities increased more with increasing UV-B radiation in P. kangdingensis than in P. cathayana, perhaps reflecting important characteristics of species with low to moderate tolerance to UV-B radiation. Overall, the results indicated that P. kangdingensis, which originates from altitudes of 3500 m, has greater tolerance to enhanced UV-B radiation than P. cathayana originating from altitudes of 1500 m. 相似文献
4.
Seedlings of Eucalyptus maculata Hook (mesic environment) and E. brockwayi C.A. Gardn. (arid environment) were supplied 100, 70 or 40% of their water requirements estimated from leaf area and the water used by well-watered seedlings. Restricting water supply caused large differences in growth rates, which were related to large differences in total leaf area. There was a fivefold range of variation in number of leaves per plant, and a reduction of up to 20% in average leaf size as a consequence of restricting water supply. Eucalyptus maculata seedlings produced more dry matter than E. brockwayi seedlings, but net assimilation rate was higher in E. brockwayi seedlings. Transpiration rates were also higher in E. brockwayi than in E. maculata. Leaf expansion was analyzed as a function of water stress integral (S(Psi)), which is the cumulative integral over time of predawn water potential below a datum. The leaf area achieved at any stress level was not uniquely dependent on total S(Psi), there was a secondary effect associated with reduced leaf growth caused by previous stress. At any value of S(Psi), reductions in leaf growth of water-stressed seedlings relative to leaf growth of well-watered control seedlings were greater in E. maculata seedlings than in E. brockwayi. Treatment differences in both species showed that, within the levels of stress applied, a moderate water stress over a long period of time was more detrimental to dry matter production than a severe stress for a short time. 相似文献
5.
We compared the physiological and morphological responses of rooted cuttings of Populus trichocarpa Torr. & Gray and P. trichocarpa x P. deltoides Bartr. ex Marsh. grown in either near-ambient solar ultraviolet-B (UV-B; 280-320 nm) radiation (cellulose diacetate film) or subambient UV-B radiation (polyester film) for one growing season. Midday biologically effective UV-B radiation was 120.6 and 1.6 mJ m(-2) s(-1) under the cellulose diacetate and polyester films, respectively. Gas exchange, leaf chlorophyll, light harvesting efficiency of photosystem II, and foliar UV-B radiation-absorbing compounds (i.e., flavonoid derivatives) were measured in expanding (leaf plastochron index (LPI) 5), nearly expanded (LPI 10), and fully expanded mature (LPI 15) leaves of intact plants of plastochron index 30 to 35. Plants were then harvested and height, diameter, biomass allocation and leaf anatomical attributes determined. Net photosynthesis, transpiration, and stomatal conductance were significantly greater in mature leaves exposed to subambient UV-B radiation than in mature leaves exposed to near-ambient UV-B radiation. Concentrations of UV-B radiation-absorbing compounds (measured as absorbance of methanol-extracts at 300 nm) were significantly greater in mature leaves exposed to near-ambient UV-B radiation than in mature leaves exposed to subambient UV-B radiation. The UV-B radiation treatments had no effects on chlorophyll content or intrinsic light harvesting efficiency of photosystem II. Height, diameter, and biomass were not significantly affected by UV-B radiation regime in either clone. Leaf anatomical development was unaffected by UV-B radiation treatment in P. trichocarpa x P. deltoides. For P. trichocarpa, leaf anatomical development was complete by LPI 10 in the near-ambient UV-B radiation treatment, but continued through to LPI 15 in the subambient UV-B radiation treatment. Mature leaves of P. trichocarpa were thicker in the subambient UV-B radiation treatment than in the near-ambient UV-B radiation treament as a result of greater development of palisade parenchyma tissue. We conclude that exposure to near-ambient UV-B radiation for one growing season caused shifts in carbon allocation from leaf development to other pools, probably including but not limited to, UV-B absorbing compounds. This reallocation curtailed leaf development and reduced photosynthetic capacity of the plants compared with those in the subambient UV-B radiation treatment and may affect growth over longer periods of exposure. 相似文献
6.
The effects of nitrate (NO(3) (-)) on acetylene reduction and growth were examined in nodulated seedlings from three open-pollinated families of black locust (Robinia pseudoacacia L.) grown in sand culture. In the first study, nine-week-old seedlings were supplied with 0.0, 0.5, 1.0, 5.0 or 15.0 mM NO(3) (-), for two weeks during which acetylene reduction and biomass were measured five times. In the second study, eight-week-old seedlings were supplied with 0.0, 1.0 or 5.0 mM NO(3) (-) for 51 days during which acetylene reduction and biomass were measured six times. Results were analyzed with and without adjustments for seedling size. In the first study, 15.0 mM NO(3) (-) significantly decreased total acetylene reduction but lower concentrations did not. In seedlings given 15.0 mM NO(3) (-), both nitrogenase activity and nodule biomass were reduced. Inhibition of nitrogenase activity by NO(3) (-) was reversible. In the second study, both the 1.0 and 5.0 mM NO(3) (-) treatments increased plant growth compared to the control (0.0 mM). At the end of the 51-day treatment period, total acetylene reduction and nodule biomass were greatest in the 1.0 mM NO(3) (-) treatment and least in the 5.0 mM NO(3) (-) treatment. However, when adjusted for seedling size, total acetylene reduction and nodule biomass were similar in the 0.0 and 1.0 mM NO(3) (-) treatments. The greater total acetylene reduction and nodule biomass of seedlings grown with 1.0 mM NO(3) (-) resulted from increased seedling size due to fertilization. After adjustment for plant size, total acetylene reduction, nodule biomass and nitrogenase activity were significantly lower in the 5.0 mM NO(3) (-) treatment compared with the control or 1.0 mM NO(3) (-) treatment. Adjustment for seedling size, by means of allometric principles, appears necessary to interpret treatment effects on total acetylene reduction and its components, nodule biomass and nitrogenase activity correctly. 相似文献
7.
Various human-induced changes to the atmosphere have caused carbon dioxide (CO?), nitrogen dioxide (NO?) and nitrate deposition (NO??) to increase in many regions of the world. The goal of this study was to examine the simultaneous influence of these three factors on tree seedlings. We used open-top chambers to fumigate sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis) with ambient or elevated CO? and NO? (elevated concentrations were 760 ppm and 40 ppb, respectively). In addition, we applied an artificial wet deposition of 30 kg ha?1 year?1 NO?? to half of the open-top chambers. After two growing seasons, hemlocks showed a stimulation of growth under elevated CO?, but the addition of elevated NO? or NO?? eliminated this effect. In contrast, sugar maple seedlings showed no growth enhancement under elevated CO? alone and decreased growth in the presence of NO? or NO??, and the combined treatments of elevated CO? with increased NO? or NO?? were similar to control plants. Elevated CO? induced changes in the leaf characteristics of both species, including decreased specific leaf area, decreased %N and increased C:N. The effects of elevated CO?, NO? and NO?? on growth were not additive and treatments that singly had no effect often modified the effects of other treatments. The growth of both maple and hemlock seedlings under the full combination of treatments (CO??+?NO??+?NO??) was similar to that of seedlings grown under control conditions, suggesting that models predicting increased seedling growth under future atmospheric conditions may be overestimating the growth and carbon storage potential of young trees. 相似文献
8.
Silver birch (Betula pendula Roth) seedlings were grown individually in containers arranged in rows radiating from a central point (Nelder plot) at densities spanning the range from 207 to 891 plants m(-2). Height of one set of seedlings was measured at weekly intervals and additional seedlings were harvested each week for dry mass and leaf area measurements. Height and shoot:root dry mass ratio increased with plant density. Seedling-to-seedling variability in dry mass, but not height, increased with increasing plant density. The red to far-red (R:FR) photon ratio in horizontally propagated radiation decreased with increasing density, even when plant densities and leaf area index values were low. In a separate experiment, elongating internodes of seedlings were irradiated locally by red and far-red light emitting diodes and stem elongation measured. Far-red light markedly increased stem elongation, suggesting that changes in light quality sensed by growing internodes are involved in the observed responses to growth density. 相似文献
9.
Lavola A 《Tree physiology》1998,18(1):53-58
A growth chamber experiment was conducted to examine the effects of UV-B exposure (4.9 kJ m(-2) day(-1) of biologically effective UV-B, 280-320 nm) on shoot growth and secondary metabolite production in Betula pendula (Roth) and B. resinifera (Britt.) seedlings originating from environments in Finland, Germany and Alaska differing in solar UV-B radiation and climate. Neither shoot growth nor the composition of secondary metabolites was affected by UV-B irradiance, but the treatment induced significant changes in the amounts of individual secondary metabolites in leaves. Leaves of seedlings exposed to UV-B radiation contained higher concentrations of several flavonoids, condensed tannins and some hydroxycinnamic acids than leaves of control seedlings that received no UV-B radiation. At the population level, there was considerable variation in secondary metabolite responses to UV-B radiation: among populations, the induced response was most prominent in Alaskan populations, which were adapted to the lowest ambient UV-B radiation environment. I conclude that solar UV-B radiation plays an important role in the formation of secondary chemical characteristics in birch trees. 相似文献
10.
11.
UV-B辐射对亚热带森林凋落叶分解的影响 总被引：3，自引：0，他引：3
采用分解袋法研究自然和UV-B辐射滤减2种环境下6种亚热带代表性树种(杉木、马尾松、木荷、香樟、青冈和甜槠)凋落叶的分解情况。结果表明:除个别分解阶段外,各树种凋落叶在2种UV-B辐射环境下的干质量剩余率均存在显著差异,且随着分解时间延长,差异逐渐加大;与对照相比,UV-B辐射滤减显著降低了6个树种凋落叶的分解速率(P<0.01),降幅为33.3%～69.6%,对香樟凋落叶分解的影响最小,对杉木凋落叶分解的影响最大;UV-B辐射处理和凋落物类型对凋落叶的分解速率均有极显著影响(P<0.001),以UV-B辐射的影响更强烈;自然和UV-B辐射滤减环境下凋落叶的分解速率均与C∶N呈显著负相关(P<0.05)。 相似文献
12.
We examined the interactive effects of elevated CO2 concentration ([CO2]) and water stress on growth and physiology of 1-year-old peach (Prunus persica L.) seedlings grown in 10-dm3 pots in open-top chambers with ambient (350 micromol mol-1) or elevated (700 micromol mol-1) [CO2]. Seedlings were supplied weekly with a non-limiting nutrient solution. Water was withheld from half of the plants in each treatment for a 4-week drying cycle, to simulate a sudden and severe water stress during the phase of rapid plant growth. Throughout the growing season, seedlings in elevated [CO2] had higher assimilation rates, measured at the growth [CO2], than seedlings in ambient [CO2], and this caused an increase in total dry mass of about 33%. Stomatal conductance, total water uptake, leaf area and leaf number were unaffected by elevated [CO2]. Because seedlings in the two CO2 treatments had similar transpiration despite large differences in total dry mass, water-use efficiency (WUE) of well-watered and water-stressed seedlings grown in elevated [CO2] was an average of 51 and 63% higher, respectively, than WUE of comparable seedlings grown in ambient [CO2]. Elevated [CO2] enhanced total biomass of water-stressed seedlings by 31%, and thus ameliorated the effects of water limitation. However, the percentage increases in total dry mass between well-watered and water-stressed seedlings were similar in ambient (53%) and elevated (58%) [CO2], demonstrating that there was no interaction between elevated [CO2] and water stress. This finding should be considered when predicting responses of trees to global climate change in hot and dry environments, where predicted temperature increases will raise evaporative demands and exacerbate the effects of drought on tree growth. 相似文献
13.
Long-term effects of enhanced UV-B radiation were evaluated in field-grown and greenhouse-grown Quercus rubra L. (northern red oak), a species with a multiple flushing shoot growth habit. Seeds were germinated and grown in ambient, twice ambient (2x) or three times ambient (3x) biologically effective UV-B radiation from square-wave (greenhouse) or modulated (field) lamp systems for three growing seasons. Greenhouse plants in the 2x treatment had greater heights and diameters during the later part of the first year and into the second year, but by the third year there were no differences among treatments. There were no significant differences in growth among treatments for field plants. Enhanced UV-B radiation did not significantly reduce total biomass or distribution of biomass in either field or greenhouse plants. Net photosynthesis (3x), leaf conductance (2x and 3x) and water-use efficiency (3x) of greenhouse plants were greater in the enhanced UV-B radiation treatments in the second year but unaffected by the treatments in other years. None of the treatments affected these parameters in field plants. Dark respiration was increased by the 3x treatment in the first and third years in greenhouse plants, and by the 2x treatment during the second year in field plants. Enhanced UV-B had variable effects on apparent quantum yield and light compensation points. Chlorophylls were unaffected by enhanced UV-B radiation in both greenhouse and field conditions. Bulk methanol-extractable UV-absorbing compounds were increased only by the 3x treatment in greenhouse plants during the third year and by the 2x treatment in field plants during the second year. Overall, Q. rubra appears relatively resistant to potentially damaging enhanced UV-B radiation and is unlikely to be negatively impacted even in the predicted worst-case scenarios. 相似文献
14.
Yellow birch (Betula alleghaniensis Britt.) seedlings were grown for three months in a greenhouse at two radiant flux densities-full light (FL) and 50% shade (LL)-and with three nitrogen sources- ammonium only (NH(4) (+)), nitrate only (NO(3) (-)) and a 1:1 mixture of ammonium and nitrate (NH(4) (+)/NO(3) (-))-in a completely randomized factorial design. The total biomass of seedlings grown under low light (LL) did not vary significantly with nitrogen source; although NO(3) (-)-treated seedlings were smaller and had a significantly lower (P 相似文献
15.
Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing,
was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4
kJ/m2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was
to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ
13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency
(WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf
total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular
CO2 concentration/ air CO2 concentration (C
i
/C
a) (4.0%), and an increase in leaf tissue δ
13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were
greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance,
δ
13C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil
water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed
over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation
between soil water content and leaf water content, δ
13C, C
i/C
a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content.
These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment,
it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.
__________
Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报] 相似文献
16.
17.
Beech seedlings (Fagus sylvatica L.) were grown in various combinations of three photosynthetic photon flux densities (PPFD, 0.7, 7.3 or 14.5 mol m(-2) day(-1)) for two years in a controlled environmental chamber. Dry mass of leaves, stem and roots, leaf area and number of leaves, and unit leaf rate were affected by both previous-year and current-year PPFD. Number of shoots and length of the main shoot were affected by previous-year PPFD but not by current-year PPFD. Number of leaves per shoot did not change with PPFD, whereas leaf dry mass/leaf area ratio was mainly affected by current-year PPFD. During the first 10 days that newly emerged seedlings were grown at a PPFD of 0.7 or 14.5 mol m(-2) day(-1), transpiration rate per unit leaf area declined. Thereafter, transpiration increased to a constant new rate. Transpiration rate per seedling was closely related to leaf area but the relationship changed with time. In two-year-old seedlings grown at various PPFD combinations of 0.7, 7.3 and 14.5 mol m(-2) day(-1) during Years 1 and 2, leaf area and transpiration rate per seedling were closely correlated at Weeks 7 and 11 after bud burst. Weak correlations were found between root dry mass and transpiration rate per seedling. During Year 2, transpiration rate per leaf area was higher at a particular PPFD in seedlings grown at a previous-year PPFD of 0.7 mol m(-2) day(-1) than in seedlings grown at a previous-year PPFD of 14.5 mol m(-2) day(-1). After transfer of two-year-old seedlings at the end of the experiment to a new PPFD (7.3 or 14.5 mol m(-2) day(-1)) for one day, transpiration rates per leaf area, measured at the new PPFD, were correlated with leaf area and root dry mass, irrespective of former PPFD treatment. 相似文献
18.
研究了不同类型的污泥(城市的、工业的和住宅污泥)对苗圃生长的银合欢幼苗田间萌发、生长和分枝的影响.播种前先将不同类型污泥的混合物与养分匮乏的自然林土壤混合.播种的3和6月后,记录幼苗大田发芽、分枝状况和其他物理生长参数(枝条或根长、活力指数、茎直径、叶片数、分枝或根鲜重和干重、总的生物量干重增长)等.与对照幼苗相比,混合污泥的土壤中生长的幼苗田间发芽、分枝状况及其他生长参数均发生了显著变化.与其它条件生长的幼苗相比,住宅污泥与土壤混合(1:1)条件生长的3月龄和6月龄幼苗分枝数和分枝鲜或干重均最高.就生长参数而言,住宅污泥与自然林土壤混合(1:1)生长的幼苗长势最好.研究表明:退化的土壤补偿以住宅污泥可促进银合欢的田间发芽、生长以及分枝的形成.图1表3参29. 相似文献
19.
Nitric oxide (NO) is an important signaling molecule involved in many physiological processes in plants. Nitric oxide generation and flavonoid accumulation are two early reactions of plants to ultraviolet-B (UV-B) irradiation. However, the source of UV-B-triggered NO generation and the role of NO in UV-B-induced flavonoid accumulation are not fully understood. In order to evaluate the origin of UV-B-triggered NO generation, we examined the responses of nitrate reductase (NR) activity and the expression levels of NIA1 and NIA2 genes in leaves of Betula pendula Roth (silver birch) seedlings to UV-B irradiation. The data show that UV-B irradiation stimulates NR activity and induces up-regulation of NIA1 but does not affect NIA2 expression during UV-B-triggered NO generation. Pretreatment of the leaves with NR inhibitors tungstate (TUN) and glutamine (Gln) abolishes not only UV-B-triggered NR activities but also UV-B-induced NO generation. Furthermore, application of TUN and Gln suppresses UV-B-induced flavonoid production in the leaves and the suppression of NR inhibitors on UV-B-induced flavonoid production can be reversed by NO via its donor sodium nitroprusside. Together, the data indicate that NIA1 in the leaves of silver birch seedlings is sensitive to UV-B and the UV-B-induced up-regulation of NIA1 may lead to enhancement of NR activity. Furthermore, our results demonstrate that NR is involved in UV-B-triggered NO generation and NR-mediated NO generation is essential for UV-B-induced flavonoid accumulation in silver birch leaves. 相似文献
20.
Leaf physiological versus morphological acclimation to high-light exposure at different stages of foliar development in oak 总被引：1，自引：0，他引：1
Rodríguez-Calcerrada J Reich PB Rosenqvist E Pardos JA Cano FJ Aranda I 《Tree physiology》2008,28(5):761-771
We investigated light acclimation in seedlings of the temperate oak Quercus petraea (Matt.) Liebl. and the co-occurring sub-Mediterranean oak Quercus pyrenaica Willd. Seedlings were raised in a greenhouse for 1 year in either 70 (HL) or 5.3% (LL) of ambient irradiance of full sunlight, and, in the following year, subsets of the LL-grown seedlings were transferred to HL either before leaf flushing (LL-HLBF plants) or after full leaf expansion (LL-HLAF plants). Gas exchange, chlorophyll a fluorescence, nitrogen fractions in photosynthetic components and leaf anatomy were examined in leaves of all seedlings 5 months after plants were moved from LL to HL. Differences between species in the acclimation of LL-grown plants to HL were minor. For LL-grown plants in HL, area-based photosynthetic capacity, maximum rate of carboxylation, maximum rate of electron transport and the effective photochemical quantum yield of photosystem II were comparable to those for plants grown solely in HL. A rapid change in nitrogen distribution among photosynthetic components was observed in LL-HLAF plants, which had the highest photosynthetic nitrogen-use efficiency. Increases in mesophyll thickness and dry mass per unit area governed leaf acclimation in LL-HLBF plants, which tended to have less nitrogen in photosynthetic components and a lower assimilation potential per unit of leaf mass or nitrogen than LL-HLAF plants. The data indicate that the phenological state of seedlings modified the acclimatory response of leaf attributes to increased irradiance. Morphological adaptation of leaves of LL-HLBF plants enhanced photosynthetic capacity per unit leaf area, but not per unit leaf dry mass, whereas substantial redistribution of nitrogen among photosynthetic components in leaves of LL-HLAF plants enhanced both mass- and area-based photosynthetic capacity. 相似文献