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1.
Zhang S  Dang QL 《Tree physiology》2006,26(11):1457-1467
To investigate the interactive effects of atmospheric carbon dioxide concentration ([CO(2)]) and nutrition on photosynthesis and its acclimation to elevated [CO(2)], a two-way factorial experiment was carried out with two nutritional regimes (high- and low-nitrogen (N), phosphorus (P) and potassium (K)) and two CO(2) concentrations (360 and 720 ppm) with white birch seedlings (Betula papyrifera Marsh.) grown for four months in environment-controlled greenhouses. Elevated [CO(2)] enhanced maximal carboxylation rate (V(cmax)), photosynthetically active radiation-saturated electron transport rate (J(max)), actual photochemical efficiency of photosystem II (PSII) in the light (DeltaF/F(m)') and photosynthetic linear electron transport to carboxylation (J(c)) after 2.5 months of treatment, and it increased net photosynthetic rate (A(n)), photosynthetic water-use efficiency (WUE), photosynthetic nitrogen-use efficiency (NUE) and photosynthetic phosphorus-use efficiency (PUE) after 2.5 and 3.5 months of treatment, but it reduced stomatal conductance (g(s)), transpiration rate (E) and the fraction of total photosynthetic linear electron transport partitioned to oxygenation (J(o)/J(T)) after 2.5 and 3.5 months of treatment. Low nutrient availability decreased A(n), WUE, V(cmax), J(max), triose phosphate utilization (TPU), (/F(m)' - F)//F(m)' and J(c), but increased J(o)/J(T) and NUE. Generally, V(cmax) was more sensitive to nutrient availability than J(max). There were significant interactive effects of [CO(2)] and nutrition over time, e.g., the positive effects of high nutrition on A(n), V(cmax), J(max), DeltaF/F(m)' and J(c) were significantly greater in elevated [CO(2)] than in ambient [CO(2)]. In contrast, the interactive effect of [CO(2)] and nutrition on NUE was significant after 2.5 months of treatment, but not after 3.5 months. High nutrient availability generally increased PUE after 3.5 months of treatment. There was evidence for photosynthetic up-regulation in response to elevated [CO(2)], particularly in seedlings receiving high nutrition. Photosynthetic depression in response to low nutrient availability was attributed to biochemical limitation (or increased mesophyll resistance) rather than stomatal limitation. Elevated [CO(2)] reduced leaf N concentration, particularly in seedlings receiving low nutrition, but had no significant effect on leaf P or K concentration. High nutrient availability generally increased area-based leaf N, P and K concentrations, but had negligible effects on K after 2.5 months of treatment.  相似文献   

2.
To investigate whether long-term elevated carbon dioxide concentration ([CO(2)]) causes declines in photosynthetic enhancement and leaf nitrogen (N) owing to limited soil fertility, we measured photosynthesis, carboxylation capacity and area-based leaf nitrogen concentration (N(a)) in Pinus taeda L. growing in a long-term free-air CO(2) enrichment (FACE) facility at an N-limited site. We also determined how maximum rates of carboxylation (V(cmax)) and electron transport (J(max)) varied with N(a) under elevated [CO(2)]. In trees exposed to elevated [CO(2)] for 5 to 9 years, the slope of the relationship between leaf photosynthetic capacity (A(net-Ca)) and N(a) was significantly reduced by 37% in 1-year-old needles, whereas it was unaffected in current-year needles. The slope of the relationships of both V(cmax) and J(max) with N(a) decreased in 1-year-old needles after up to 9 years of growth in elevated [CO(2)], which was accompanied by a 15% reduction in N allocation to the carboxylating enzyme. Nitrogen fertilization (110 kg N ha(-1)) in the ninth year of exposure to elevated [CO(2)] restored the slopes of the relationships of V(cmax) and J(max) with N(a) to those of control trees (i.e., in ambient [CO(2)]). The J(max):V(cmax) ratio was unaffected by either [CO(2)] or N fertilization. Changes in the apparent allocation of N to photosynthetic components may be an important adjustment in pines exposed to elevated [CO(2)] on low-fertility sites. We conclude that fundamental relationships between photosynthesis or its component processes with N(a) may be altered in aging pine needles after more than 5 years of exposure to elevated atmospheric [CO(2)].  相似文献   

3.
Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings were supplied with solutions containing nitrogen (N) at 0.1 x or 2 x the optimum rate (low-N and high-N supply, respectively) and grown either outside in a control plot or inside open-top chambers and exposed to ambient (355 &mgr;mol mol(-1)) or elevated (700 &mgr;mol mol(-1)) CO(2) concentration ([CO(2)]). Gas exchange measurements, chlorophyll determinations and nutrient analysis were made on current-year (< 1-year-old) shoots of the upper whorl after the seedlings had been growing in the [CO(2)] treatments for 17 months and the nutrient treatments for 6 months. Total seedling biomass and biomass allocation were assessed at the end of the experiment. Nutrient treatment had a significant effect on the light response curves, irrespective of [CO(2)] or chamber treatment; seedlings supplied with high-N rates had higher net photosynthetic rates than seedlings supplied with low-N rates. The degree of photosynthetic stimulation in response to elevated [CO(2)] was larger in seedlings receiving high-N rates than in seedlings receiving low-N rates. Light-saturated net photosynthesis of seedlings grown and measured in elevated [CO(2)] was 26% higher than that of seedlings grown and measured in ambient [CO(2)]. There was no significant effect of [CO(2)] or chamber treatment on the CO(2) response curves of seedlings receiving High-N supply rates. In contrast, analysis of the CO(2) response curves of seedlings receiving Low-N supply rates showed acclimation to elevated [CO(2)]. Both maximum rate of carboxylation (V(cmax)) and maximum electron transport capacity (J(max)) were lower and J(max)/V(cmax) higher in seedlings in the elevated [CO(2)] treatment. There was no effect of elevated [CO(2)] on stomatal conductance, although it was highly dependent on foliar [N], ranging from ~60 mmol m(-2) s(-1) at ~1.5 g N m(-2) to 200 mmol m(-2) s(-1) at ~5 g N m(-2). In the high-N and low-N treatments, foliar N concentration was 10 and 28% lower in seedlings grown in elevated [CO(2)] than in seedlings grown in ambient [CO(2)], respectively. There was no [CO(2)] effect on foliar phosphorus concentration ([P]). Chlorophyll concentration increased with increasing N supply in all treatments. There was no significant effect of elevated [CO(2)] on specific leaf area. Chlorophyll concentration expressed either on an area or dry mass basis for a given foliar [N] was higher in seedlings grown in elevated [CO(2)] than in seedings grown in ambient [CO(2)]. Elevated [CO(2)] increased total biomass accumulation by 37% in seedlings in the high-N treatment but had no effect in seedlings in the low-N treatment. There was a proportionally bigger allocation of biomass to roots of seedlings in the elevated [CO(2)] + low-N supply rate treatment compared with seedlings in other treatments. This resulted in a reduction in aboveground biomass compared with corresponding seedlings grown in ambient [CO(2)].  相似文献   

4.
To assess the effects of elevated CO(2) concentration ([CO(2)]) on the photosynthetic properties around spring budbreak, we monitored the total leaf sugar and starch content, and chlorophyll fluorescence in 1-year-old needles of Sakhalin spruce (Picea glehnii Masters) seedlings in relation to the timing of budbreak, grown in a phytotron under natural daylight at two [CO(2)] levels (ambient: 360?μmol mol(-1) and elevated: 720?μmol mol(-1)). Budbreak was accelerated by elevated [CO(2)] accompanied with earlier temporal declines in the quantum yield of PSII electron transport (Φ(PSII)) and photochemical quenching (q(L)). Plants grown under elevated [CO(2)] showed pre-budbreak leaf starch content twice as high with no significant difference in Φ(PSII) from ambient-CO(2)-grown plants when compared at the same measurement [CO(2)], i.e., 360 or 720?μmol mol(-1), suggesting that the enhanced pre-budbreak leaf starch accumulation might not cause down-regulation of photosynthesis in pre-existing needles under elevated [CO(2)]. Conversely, lower excitation pressure adjusted for the efficiency of PSII photochemistry ((1?-?q(P)) F(v)'/F(m)') was observed in plants grown under elevated [CO(2)] around budbreak when compared at their growth [CO(2)] (i.e., comparing (1?-?q(P)) F(v)'/F(m)' measured at 720?μmol mol(-1) in elevated-CO(2)-grown plants with that at 360?μmol mol(-1) in ambient-CO(2)-grown plants), which suggests lower rate of photoinactivation of PSII in the elevated-CO(2)-grown plants around spring budbreak. The degree of photoinhibition, as indicated by the overnight-dark-adapted F(v)/F(m), however, showed no difference between CO(2) treatments, thereby suggesting that photoprotection during the daytime or the repair of PSII at night was sufficient to alleviate differences in the rate of photoinactivation.  相似文献   

5.
The effects of increased CO(2) and temperature on the photosynthetic capacity of Siberian white birch and Japanese white birch (Betula platyphylla Sukatch. and B. platyphylla Sukatch. var. japonica Hara) were measured. Birch seedlings were raised with a CO(2) partial pressure of 36 +/- 0.3 Pa (i.e., ambient) or 70 +/- 0.6 Pa at day/night temperatures of either 30/16 degrees C or 26/12 degrees C. Siberian birch leaves were smaller and thicker than Japanese birch leaves. Water use efficiency and nitrogen use efficiency of Siberian birch grown in the CO(2)-enriched air were higher than those of Japanese birch. Both species showed a physiological adjustment to the growth CO(2) partial pressure. Carboxylation efficiency and quantum yield of both species grown in CO(2)-enriched air were lower than those of seedlings grown in ambient CO(2). The adaptation of Siberian and Japanese birch to elevated CO(2) and temperature are discussed in relation to predicted climate change.  相似文献   

6.
We demonstrated that the inorganic phosphate (P(i)) requirement for growth of Japanese red pine (Pinus densiflora Sieb. & Zucc.) seedlings is increased by elevated CO(2) concentration ([CO(2)]) and that responses of the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch to P(i) supply are also altered. To investigate the growth response of non-mycorrhizal seedlings to P(i) supply in elevated [CO(2)], non-mycorrhizal seedlings were grown for 73 days in ambient or elevated [CO(2)] (350 or 700 micromol mol(-1)) with nutrient solutions containing one of seven phosphate concentrations (0, 0.02, 0.04, 0.06, 0.08, 0.10 and 0.20 mM). In ambient [CO(2)], the growth response to P(i) was saturated at about 0.1 mM P(i), whereas in elevated [CO(2)], the growth response to P(i) supply did not saturate, even at the highest P(i) supply (0.2 mM), indicating that the P(i) requirement is higher in elevated [CO(2)] than in ambient [CO(2)]. The increased requirement was due mainly to an altered shoot growth response to P(i) supply. The enhanced P(i) requirement in elevated [CO(2)] was not associated with a change in photosynthetic response to P(i) or a change in leaf phosphorus (P) status. We investigated the effect of P(i) supply (0.04, 0.08 and 0.20 mM) on the ectomycorrhizal fungus P. tinctorius in mycorrhizal seedlings grown in ambient or elevated [CO(2)]. Root ergosterol concentration (an indicator of fungal biomass) decreased with increasing P(i) supply in ambient [CO(2)], but the decrease was far less in elevated [CO(2)]. In ambient [CO(2)] the ratio of extramatrical mycelium to root biomass decreased with increasing P(i) supply but did not change in elevated [CO(2)]. We conclude that, because elevated [CO(2)] increased the P(i) requirement for shoot growth, the significance of the ectomycorrhizal association was also increased in elevated [CO(2)].  相似文献   

7.
Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO(2) ([CO(2)]) or O(3) ([O(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. The trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwintering buds and early leaf development during the 8th-9th year of free-air CO(2) and O(3) exposure at the Aspen FACE site located near Rhinelander, WI. Net photosynthesis was enhanced 49-73% by elevated [CO(2)], and decreased 13-30% by elevated [O(3)]. Elevated [CO(2)] delayed, and elevated [O(3)] tended to accelerate, leaf abscission in autumn. Elevated [CO(2)] increased the ratio of monosaccharides to di- and oligosaccharides in aspen buds, which may indicate a lag in cold acclimation. The total carbon concentration in overwintering buds was unaffected by the treatments, although elevated [O(3)] decreased the amount of starch by 16% in birch buds, and reduced the size of aspen buds, which may be related to the delayed leaf development in aspen during the spring. Elevated [CO(2)] generally ameliorated the effects of elevated [O(3)]. Our results show that both elevated [CO(2)] and elevated [O(3)] have the potential to alter carbon metabolism of overwintering buds. These changes may cause carry-over effects during the next growing season.  相似文献   

8.
If an increase in temperature will limit the growth of a species, it will be in the warmest portion of the species distribution. Therefore, in this study we examined the effects of elevated temperature on net carbon assimilation and biomass production of northern red oak (Quercus rubra L.) seedlings grown near the southern limit of the species distribution. Seedlings were grown in chambers in elevated CO(2) (700 μmol mol(-1)) at three temperature conditions, ambient (tracking diurnal and seasonal variation in outdoor temperature), ambient +3 °C and ambient +6 °C, which produced mean growing season temperatures of 23, 26 and 29 °C, respectively. A group of seedlings was also grown in ambient [CO(2)] and ambient temperature as a check of the growth response to elevated [CO(2)]. Net photosynthesis and leaf respiration, photosynthetic capacity (V(cmax), J(max) and triose phosphate utilization (TPU)) and chlorophyll fluorescence, as well as seedling height, diameter and biomass, were measured during one growing season. Higher growth temperatures reduced net photosynthesis, increased respiration and reduced height, diameter and biomass production. Maximum net photosynthesis at saturating [CO(2)] and maximum rate of electron transport (J(max)) were lowest throughout the growing season in seedlings grown in the highest temperature regime. These parameters were also lower in June, but not in July or September, in seedlings grown at +3 °C above ambient, compared with those grown in ambient temperature, indicating no impairment of photosynthetic capacity with a moderate increase in air temperature. An unusual and potentially important observation was that foliar respiration did not acclimate to growth temperature, resulting in substantially higher leaf respiration at the higher growth temperatures. Lower net carbon assimilation was correlated with lower growth at higher temperatures. Total biomass at the end of the growing season decreased in direct proportion to the increase in growth temperature, declining by 6% per 1 °C increase in mean growing season temperature. Our observations suggest that increases in air temperature above current ambient conditions will be detrimental to Q. rubra seedlings growing near the southern limit of the species range.  相似文献   

9.
Temperature effects on photosynthesis were studied in seedlings of evergreen Mediterranean cork oak (Quercus suber L.). Responses to changes in temperature and the temperature optima of maximal carboxylation rate (V(cmax)) and maximal light-driven electron flux (J(max)) were estimated from gas exchange measurements and a leaf-level photosynthesis model. The estimated temperature optima were approximately 34 and 33 degrees C for V(cmax) and J(max), respectively, which fall within the lower range of temperature optima previously observed in deciduous tree species. The thermostability of the photosynthetic apparatus was estimated according to the temperature at which basal chlorophyll a fluorescence begins to increase (T(c)). The T(c) was highly variable, increasing from 42 to 51 degrees C when ambient temperature rose from 10 to 40 degrees C, and increasing from 44 to 54 degrees C with decreasing soil water availability while net CO(2) assimilation rate dropped to almost zero. When a heat shock was imposed, an additional small increase in T(c) was observed in drought-stressed and control seedlings. Maximal T(c) values following heat shock were about 56 degrees C, which, to our knowledge, are the highest values that have been observed in tree species. In conclusion, the intrinsic temperature responses of cork oak did not differ from those of other species (similar T(c) under ambient temperature and water availability, and relatively low thermal optima for photosynthetic capacity in seedlings grown at cool temperatures). However, the large ability of cork oak to acclimate to drought and elevated temperature may be an important factor in the tolerance of this evergreen Mediterranean species to summer drought and high temperatures.  相似文献   

10.

Improving drought tolerance of container seedlings of Japanese larch is of high importance to afforestation. We hypothesized that adequate nitrogen (N) and limited water supply would increase the tolerance of container seedlings to water-deficit stress, circumventing photoinhibition, by means of (i) enhanced photosynthetic capacity with higher leaf N and (ii) decreased water loss from leaves with lower biomass allocation into aboveground parts. Container seedlings of Japanese larch were grown under the treatment combinations of adequate (+?N: 300 mg N container?1) or limited (??N: 150 mg N container?1) N and adequate (+?W: daily irrigation) or limited (??W: twice-a-week irrigation) water. Then, seedlings were subjected to a progressive drought treatment. Higher leaf N was observed in container seedlings grown under?+?N and???W. During progressive drought, lower stomatal conductance and net photosynthetic rate were observed in leaves with higher leaf N at a given predawn leaf water potential. Furthermore, the maximum efficiency of PSII photochemistry (Fv/Fm) was lower in leaves with higher leaf N, suggesting that higher leaf N might impair intrinsic tolerance to drought at the leaf level contrary to expectations. Conversely,???N and???W seedlings with lower shoot biomass delayed soil drying as a whole-plant response via a reduction in leaf transpiration, leading to delayed photoinhibition as indicated by a decline in Fv/Fm. To circumvent stress at the initial stage of water deficit, lower leaf N via limited N regime and smaller shoot biomass driven by limited N and water regimes would be important.

  相似文献   

11.
Tissue DT  Lewis JD 《Tree physiology》2010,30(11):1361-1372
Plants often exhibit proportionately larger photosynthetic responses to the transition from glacial to modern [CO(2)] than from modern to future [CO(2)]. Although this pattern may reflect increased nutrient demand with increasing [CO(2)], few studies have examined the role of nutrient supply in regulating responses to the range of [CO(2)] from glacial to future [CO(2)]. In this study, we examined the effects of P supply (0.004-0.5 mM) on photosynthetic responses of Populus deltoides (cottonwood) seedlings to glacial (200 micromol mol(-1)), modern (350 μmol mol(-1)) and future (700 micromol mol(-1)) [CO(2)]. The A(sat) (light-saturated net photosynthetic rates at the growth [CO(2)]) response to future [CO(2)] decreased with decreasing P supply such that there was no response at the lowest P supply. However, P supply did not affect A(sat) responses to an increase from glacial to modern [CO(2)]. Photosynthetic capacity [e.g., final rubisco activity, apparent, maximal Rubisco-limited rate of photosynthesis (V(cmax)), apparent, maximal electron transport-limited rate of photosynthesis (J(max))], stomatal conductance (g(s)) and leaf P generally increased with increasing P supply but decreased with increasing [CO(2)]. Measures of carbohydrate sink capacity (e.g., leaf mass per unit leaf area, leaf starch) increased with both increasing P supply and increasing [CO(2)]. Changes in V(cmax) and g(s) together accounted for 78% of the variation in A(sat) among [CO(2)] and P treatments, suggesting significant biochemical and stomatal controls on photosynthesis. However, A(sat) responses to increasing [CO(2)] did not reflect the changes in the carbohydrate sink capacity. These results have important implications because low P already constrains responses to increasing [CO(2)] in many ecosystems, and our results suggest that the P demand will increasingly affect A(sat) in cottonwood as [CO(2)] continues to increase.  相似文献   

12.
Gas exchange was measured in a forest plantation dominated by Fraxinus angustifolia Vahl. and Quercus robur L. in northern Italy, over three growing seasons that differed in water availability (2001, 2002 and 2003). The objectives were to: (1) determine variability in the photosynthetic parameters V(cmax) (maximum carboxylation capacity) and J(max) (maximum rate of electron transport) in relation to species, leaf ontogeny and drought; and (2) assess the potential of the photosynthesis-nitrogen relationship for estimating leaf photosynthetic capacity. Marked seasonal and interannual variability in photosynthetic capacity was observed, primarily caused by changes in leaf ontogeny and water stress. Relatively small differences were apparent between species. In the absence of water stress (year 2002), the seasonal patterns of V(cmax) and J(max) were characterized by a rapid increase during spring, a relatively steady state during summer and a rapid decline during autumn. In years with a moderate (year 2001) or a severe (year 2003) water stress, photosynthetic capacity decreased during the summer in proportion to drought intensity, without a parallel decline in leaf nitrogen content. The V(cmax)-nitrogen relationship was significantly affected by both leaf ontogeny and drought. As a consequence, the use of a single annual regression to predict V(cmax) from leaf nitrogen yielded good estimates only during the summer and in the absence of water stress. Irrespective of the mechanisms by which photosynthetic capacity is affected by water stress, its large seasonal and interannual variability is of great relevance for modeling the forest carbon cycle.  相似文献   

13.
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   

14.
Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water flux in wet soil, suggesting that the responses of J(s,r) to environmental factors cannot be directly inferred from day-time patterns. Changes in J(s,r) are likely to influence pre-dawn leaf water potential, and plant responses to water stress. Nocturnal fluxes are clearly important for predicting effects of climate change on forest physiology and hydrology.  相似文献   

15.
We investigated the interactive effects of elevated concentrations of carbon dioxide ([CO(2)]) and ozone ([O(3)]) on radial growth, wood chemistry and structure of five 5-year-old trembling aspen (Populus tremuloides Michx.) clones and the wood chemistry of paper birch (Betula papyrifera Marsh.). Material for the study was collected from the Aspen FACE (free-air CO(2) enrichment) experiment in Rhinelander, WI, where the saplings had been exposed to four treatments: control, elevated [CO(2)] (560 ppm), elevated [O(3)] (1.5 x ambient) and their combination for five growing seasons. Wood properties of both species were altered in response to exposure to the treatments. In aspen, elevated [CO(2)] decreased uronic acids (constituents of, e.g., hemicellulose) and tended to increase stem diameter. In response to elevated [O(3)] exposure, acid-soluble lignin concentration decreased and vessel lumen diameter tended to decrease. Elevated [O(3)] increased the concentration of acetone-soluble extractives in paper birch, but tended to decrease the concentration of these compounds in aspen. In paper birch, elevated [CO(2)] decreased and elevated [O(3)] increased starch concentration. The responses of wood properties to 5 years of fumigation differed from those previously reported after 3 years of fumigation.  相似文献   

16.
Cao B  Dang QL  Zhang S 《Tree physiology》2007,27(6):891-899
To study the effects of elevated CO2 concentration ([CO2]) on relationships between nitrogen (N) nutrition and foliar gas exchange parameters, white birch (Betula papyrifera Marsh.) seedlings were exposed to one of five N-supply regimes (10, 80, 150, 220, 290 mg N l(-1)) in either ambient [CO2] (360 micromol mol(-1)) or elevated [CO2] (720 micromol mol(-1)) in environment-controlled greenhouses. Foliar gas exchange and chlorophyll fluorescence were measured after 60 and 80 days of treatment. Photosynthesis showed a substantial down-regulation (up to 57%) in response to elevated [CO2] and the magnitude of the down-regulation generally decreased exponentially with increasing leaf N concentration. When measured at the growth [CO2], elevated [CO2] increased the overall rate of photosynthesis (P(n)) and instantaneous water-use efficiency (IWUE) by up to 69 and 236%, respectively, but decreased transpiration (E) and stomatal conductance (g(s)) in all N treatments. However, the degree of stimulation of photosynthesis by elevated [CO2] decreased as photosynthetic down-regulation increased from 60 days to 80 days of treatment. Elevated [CO2] significantly increased total photosynthetic electron transport in all N treatments at 60 days of treatment, but the effect was insignificant after 80 days of treatment. Both P(n) and IWUE generally increased with increasing leaf N concentration except at very high leaf N concentrations, where both P(n) and IWUE declined. The relationships of P(n) and IWUE with leaf N concentration were modeled with both a linear regression and a second-order polynomial function. Elevated [CO2] significantly and substantially increased the slope of the linear regression for IWUE, but had no significant effect on the slope for P(n). The optimal leaf N concentration for P(n) and IWUE derived from the polynomial function did not differ between the CO2 treatments when leaf N was expressed on a leaf area basis. However, the mass-based optimal leaf N concentration for P(n) was much lower in seedlings in elevated [CO2] than in ambient [CO2] (31.88 versus 37.00 mg g(-1)). Elevated [CO2] generally decreased mass-based leaf N concentration but had no significant effect on area-based leaf N concentration; however, maximum N concentration per unit leaf area was greater in elevated [CO2] than in ambient [CO2] (1.913 versus 1.547 g N m(-2)).  相似文献   

17.
We used gas exchange techniques to estimate maximum rate of carboxylation (V(cmax)), a measure of photosynthetic capacity, in the understory and upper crown of a closed deciduous forest over two seasons. There was extensive variability in photosynthetic capacity as a result of vertical canopy position, species type, leaf age and drought. Photosynthetic capacity was greater in oaks than in maples and greater in the overstory than in the understory. Parameter V(cmax) was maximal early in the season but declined slowly throughout most of the summer, and then more rapidly during senescence. There was also an apparent decline during drought in some trees. Variability in V(cmax) as a result of species or vertical canopy gradients was described well by changes in leaf nitrogen per unit area (N(a)). However, temporal changes in V(cmax) were often poorly correlated with leaf nitrogen, especially in spring and summer and during drought. This poor correlation may be the result of a seasonally dependent fractional allocation of leaf nitrogen to Rubisco; however, we could not discount Rubisco inactivation, patchy stomatal closure or changes in mesophyll resistance. Consequently, when a single annual regression equation of V(cmax) versus N(a) was used for this site, there were substantial errors in the temporal patterns in V(cmax) that will inevitably result in modeling errors.  相似文献   

18.
Pedunculate oak (Quercus robur L.) seedlings were grown for 3 or 4 months (second- and third-flush stages) in greenhouses at two atmospheric CO2 concentrations ([CO2]) (350 or 700 micromol mol(-1)) and two nitrogen fertilization regimes (6.1 or 0.61 mmol N l(-1) nutrient solution). Combined effects of [CO2] and nitrogen fertilization on partitioning of newly acquired carbon (C) and nitrogen (N) were assessed by dual 13C and 15N short-term labeling of seedlings at the second- or third-flush stage of development. In the low-N treatment, root growth, but not shoot growth, was stimulated by elevated [CO2], with the result that shoot/root biomass ratio declined. At the second-flush stage, overall seedling biomass growth was increased (13%) by elevated [CO2] regardless of N fertilization. At the third-flush stage, elevated [CO2] increased growth sharply (139%) in the high-N but not the low-N treatment. Root/shoot biomass ratios were threefold higher in the low-N treatment relative to the high-N treatment. At the second-flush stage, leaf area was 45-51% greater in the high-N treatment than in the low-N treatment. At the-third flush stage, there was a positive interaction between the effects of N fertilization and [CO2] on leaf area, which was 93% greater in the high-N/elevated [CO2] treatment than in the low-N/ambient [CO2] treatment. Specific leaf area was reduced (17-25%) by elevated [CO2], whereas C and N concentrations of seedlings increased significantly in response to either elevated [CO2] or high-N fertilization. At the third-flush stage, acquisition of C and N per unit dry mass of leaf and fine root was 51 and 77% greater, respectively, in the elevated [CO2]/high-N fertilization treatment than in the ambient [CO2]/low-N fertilization treatment. However, there was dilution of leaf N in response to elevated [CO2]. Partitioning of newly acquired C and N between shoot and roots was altered by N fertilization but not [CO2]. More newly acquired C and N were partitioned to roots in the low-N treatment than in the high-N treatment.  相似文献   

19.
Responses of photosynthesis (A) to intercellular CO(2) concentration (C(i)) were measured in a fast- and a slow-growing clone of Pinus radiata D. Don cultivated in a greenhouse with a factorial combination of nitrogen and phosphorus supply. Stomatal limitations scaled with nitrogen and phosphorus supply as a fixed proportion of the light-saturated photosynthetic rate (18.5%) independent of clone. Photosynthetic rates at ambient CO(2) concentration were mainly in the V(cmax)-limited portion of the CO(2) response curve at low-nitrogen supply and at the transition between V(cmax) and J(max) at high-nitrogen supply. Nutrient limitations to photosynthesis were partitioned based on the ratio of foliage nitrogen to phosphorus expressed on a leaf area basis (N(a)/P(a)), by minimizing the mean square error of segmented linear models relating photosynthetic parameters (V(cmax), J(max), T(p)) to foliar nitrogen and phosphorus concentrations. A value of N(a)/P(a) equal to 23 (mole basis) was identified as the threshold separating nitrogen (N(a)/P(a) < or = 23) from phosphorus (N(a)/P(a) > 23) limitations independent of clones. On an area basis, there were significant positive linear relationships between the parameters, V(cmax), J(max), T(p) and N(a) and P(a), but only the relationships between T(p) and N(a) and P(a) differed significantly between clones. These findings suggest that, in genotypes with contrasting growth, the responses of V(cmax) and J(max) to nutrient limitation are equivalent. The relationships between the parameters V(cmax), J(max), T(p) and foliage nutrient concentration on a mass basis were unaffected by clone, because the slow-growing clone had a significantly greater leaf area to mass ratio than the fast-growing clone. These results may be useful in discriminating nitrogen-limited photosynthesis from phosphorus-limited photosynthesis.  相似文献   

20.
We investigated growth, leaf monoterpene emission, gas exchange, leaf structure and leaf chemical composition of 1-year-old Quercus ilex L. seedlings grown in ambient (350 microl l(-1)) and elevated (700 microl l(-1)) CO2 concentrations ([CO2]). Monoterpene emission and gas exchange were determined at constant temperature and irradiance (25 degrees C and 1000 micromol m(-2) s(-1) of photosynthetically active radiation) at an assay [CO2] of 350 or 700 microl l(-1). Measurements were made on intact shoots after the end of the growing season between mid-October and mid-February. On average, plants grown in elevated [CO2] had significantly increased foliage biomass (about 50%). Leaves in the elevated [CO2] treatment were significantly thicker and had significantly higher concentrations of cellulose and lignin and significantly lower concentrations of nitrogen and minerals than leaves in the ambient [CO2] treatment. Leaf dry matter density and leaf concentrations of starch, soluble sugars, lipids and hemi-cellulose were not significantly affected by growth in elevated [CO2]. Monoterpene emissions of seedlings were significantly increased by elevated [CO2] but were insensitive to short-term changes in assay [CO2]. On average, plants grown in elevated [CO2] had 1.8-fold higher monoterpene emissions irrespective of the assay [CO2]. Conversely, assay [CO2] rapidly affected photosynthetic rate, but there was no apparent long-term acclimation of photosynthesis to growth in elevated [CO2]. Regardless of growth [CO2], photosynthetic rates of all plants almost doubled when the assay [CO2] was switched from 350 to 700 microl l(-1). At the same assay [CO2], mean photosynthetic rates of seedlings in the two growth CO2 treatments were similar. The percentage of assimilated carbon lost as monoterpenes was not significantly altered by CO2 enrichment. Leaf emission rates were correlated with leaf thickness, leaf concentrations of cellulose, lignin and nitrogen, and total plant leaf area. In all plants, monoterpene emissions strongly declined during the winter independently of CO2 treatment. The results are discussed in the context of the acquisition and allocation of resources by Q. ilex seedlings and evaluated in terms of emission predictions.  相似文献   

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