共查询到20条相似文献，搜索用时 15 毫秒
1.
Comparison of photosynthetic induction and transient limitations during the induction phase in young and mature leaves from three poplar clones 总被引：1，自引：0，他引：1
Urban O Sprtová M Kosvancová M Tomásková I Lichtenthaler HK Marek MV 《Tree physiology》2008,28(8):1189-1197
We tested the hypothesis that leaf age affects photosynthetic induction, because conductance to CO2 diffusion usually decreases with increasing leaf age. Photosynthetic inductions, primarily determined by the light modulation of Rubisco activity and stomatal opening, were investigated in both young and mature leaves, as defined by leaf plastochron index (LPI), from three poplar clones: Populus alba L., P. nigra L. and P. x euramericana (Dode) Guinier. In all clones, maximum assimilation rates (A max), maximum stomatal conductance (G Smax) and dark respiration rates (RD) were higher in young leaves (LPI = 3-5) than in mature leaves (LPI = 10-14), and A max decreased from P. alba via P. x euramericana to P. nigra. The clones with high photosynthetic capacity had low induction states 60 s after leaf illumination (IS60; indicating a slow initial induction phase), and required less time to reach 90% photosynthetic induction (T90). In contrast, the clone with the lowest photosynthetic capacity (P. nigra) exhibited high IS60 (high initial induction state) but a long induction time (high T90). A comparison of mature leaves with young leaves revealed significantly (P < 0.01) lower IS60 values in mature leaves of P. nigra only, and significantly higher T90 values in mature leaves of P. alba only. In all clones, young leaves exhibited a lower percentage of maximum transient stomatal limitation during photosynthetic induction (4-9%) compared with mature leaves (16-30%). Transient biochemical limitation, assessed on the basis of the time constants of Rubisco activation (tau), was significantly higher in mature leaves than in young leaves of P. alba; whereas there were no significant differences in tau between young and mature leaves of the other poplar clones. Thus, our hypothesis that leaf age affects photosynthetic induction was confirmed at the level of transient stomatal limitation, which was significantly higher in mature leaves than in young leaves in all clones. For the induction parameters IS60, T90 and tau, photosynthetic induction was more clone-specific and was dependent on leaf age only in some cases, an observation that may apply to other tree species. 相似文献
2.
At the intra-plant level, temporal and spatial variations in plant defense traits can be influenced by resource requirements, defensive priorities and storage opportunities. Across a leaf age gradient, cyanogenic glycoside concentrations in the rainforest understory tree Ryparosa kurrangii B.L. Webber were higher in young expanding leaves than in mature leaves (2.58 and 1.38 mg g(-1), respectively). Moreover, cyanogens, as an effective chemical defense against generalist herbivores, contributed to a defense continuum protecting foliar tissue during leaf development. Chemical (cyanogens and phenolic compounds) and phenological (delayed greening) defense traits protected young leaves, whereas mature leaves were largely protected by physical defense mechanisms (lamina toughness; explained primarily by leaf mass per area). Cyanogen concentration was considerably higher in floral tissue than in foliar tissue and decreased in floral tissue during development. Across contrasting tropical seasons, foliar cyanogenic concentration varied significantly, being highest in the late wet season and lowest during the pre-wet season, the latter coinciding with fruiting and leaf flushing. Cyanogens in R. kurrangii appear to be differentially allocated in a way that maximizes plant fitness but may also act as a store of reduced nitrogen that is remobilized during flowering and leaf flushing. 相似文献
3.
The canopy structure and within-stand light conditions of several young birch (Betula pendula Roth. and B. pubescens Ehrh.) stands were studied. In addition, 2-year-old silver birch seedlings were subjected to varying degrees of artificial shading for one growing season in order to interpret the results of the former experiments. The shading increased the specific leaf area and the thickness of leaf mesophyll was reduced by increased shading. Similarly, the maximum photosynthetic rate and the light intensity for photosynthetic saturation were decreased in shading. Both phenomena seemed to be associated with the increase in specific leaf area and the decrease in the amount of chlorophyll per unit of leaf area. 相似文献
4.
5.
Aboveground xylem hydraulic conductance was determined in Scots pine (Pinus sylvestris L.) trees and stands from 7 to about 60 years of age. At the stand scale, leaf area index and net primary productivity (NPP, above- plus belowground) increased and reached a plateau at about 25-30 and 15-20 years, respectively; both parameters declined in mature stands. Stand hydraulic conductance followed a similar trend to NPP, with a maximum at about 15-20 years and a pronounced reduction in old stands. At the tree scale, annual biomass growth per unit of leaf area (growth efficiency) declined with tree age, whereas aboveground sapwood volume per unit leaf area, which is linearly related to maintenance respiration costs, steadily increased. Radiation interception per unit leaf area increased significantly with reduced leaf area index of mature stands, despite increased foliage clumping in the canopies of mature trees. Needle nutrient concentration did not change in the chronosequence. Tree hydraulic conductance per unit leaf area was strongly and positively correlated with growth efficiency. We discuss our findings in the context of growth reductions in mature and old trees, and suggest that increased hydraulic resistance and maintenance respiration costs may be the main causes of reduced carbon gain in mature and old trees. 相似文献
6.
In two different experiments the urediniospores of Melampsoridium betulinum from Betula pendula and Betula pubescens germinated both on mature leaves of greenhouse-grown plants and on sterile in vitro leaves of micropropagated plantlets, which were cloned from the same B. pendula and B. pubescens genotypes. The urediniospores and germ tubes were more easily detached from the leaf surfaces of in vitro leaves. If germination took place on a leaf vein, the growth continued across the veinal ridges; otherwise, no determined growth towards the stomata could be observed with either of the leaf types studied. In both experiments on the in vitro leaves of B. pubescens clone V5944, the germ tubes of the rust isolate from B. pendula mislocated appressoria significantly more often than the germ tubes of the rust isolate from B. pubescens. On the mature leaves of B. pendula clone E4214 and B. pubescens clone V5940 there were also significant differences in appressorial locations between the two rust isolates but the clonal responses were inconsistent. The results of the inoculations suggest that the incompatibility of the rust isolates from B. pendula on the leaves of B. pubescens is not related to the significantly higher ratio of failures in locating appressoria in this host-rust combination. 相似文献
7.
Dryobalanops aromatica Gaertn. f. is a major tropical canopy species in lowland tropical rain forests in Peninsular Malaysia. Diurnal changes in net photosynthetic rate (A) and stomatal conductance to water vapor (g(s)) were measured in fully expanded young and old leaves in the uppermost canopy (35 m above ground). Maximum A was 12 and 10 micro mol m(-2) s(-1) in young and old leaves, respectively; however, because of large variation in A among leaves, mean maximum A in young and old leaves was only 6.6 and 5.5 micro mol m(-2) s(-1), respectively. Both g(s) and A declined in young leaves when T(leaf) exceeded 34 degrees C and leaf-to-air vapor pressure deficit (DeltaW) exceeded 0.025, whereas in old leaves, g(s) and A did not start to decline until T(leaf) and DeltaW exceeded 36 degrees C and 0.035, respectively. Under saturating light conditions, A was linearly related to g(s). The coefficient of variation (CV) for the difference between the CO(2) concentrations of ambient air and the leaf intercellular air space (C(a) - C(i)) was smaller than the CV for A or g(s), suggesting that maximum g(s) was mainly controlled by mesophyll assimilation (A/C(i)). Minimum C(i)/C(a) ratios were relatively high (0.72-0.73), indicating a small drought-induced stomatal limitation to A and non-conservative water use in the uppermost canopy leaves. 相似文献
8.
Neutral lipids were analyzed in stem wood of a 7-year-old clone and in five 35-70-year-old mature trees of silver birch (Betula pendula Roth). In young trees and in mature wood of old trees, the free fatty acid fraction comprised less than 5% of the concentration of triacylglycerols (TG). The concentration of free linoleic acid was lowest in March when the young trees were dormant and highest during midsummer and September. In mature trees, the TG concentration increased toward the pith, indicating that living parenchyma cells close to the pith have a large TG storage capacity. The TG concentration (mean 0.51 +/- 0.02% of wood dry mass) remained constant throughout the year in young trees, whereas the concentration of beta-sitosterol, the dominant free sterol (mean 82.5 +/- 0.4% of total free sterols), decreased during spring and early summer when the temperature gradually increased, and increased during autumn when the trees became dormant. In young trees, we detected a seasonal interconversion between the free and esterified forms of beta-sitosterol and campesterol, and within the steryl ester fraction between squalene and betulaprenol-7. The concentration of esterified sterols/isoprenoids was exceptionally high, especially in the inner regions of mature stem wood (mean 0.6 +/- 0.03% of wood dry mass). No heartwood formation was detected. 相似文献
9.
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
10.
Changes in gas exchange with leaf age and fruit growth were determined in lychee trees (Litchi chinensis Sonn.) growing in subtropical Queensland (27 degrees S). Leaves expanded in a sigmoid pattern over 50 days during spring, with net CO2 assimilation (A) increasing from -4.1 +/- 0.9 to 8.3 +/- 0.5 micromol m-2 s-1 as the leaves changed from soft and red, to soft and light green, to hard and dark green. Over the same period, dark respiration (Rd) decreased from 5.0 +/- 0.8 to 2.0 +/- 0.1 micromol CO2 m-2 s-1. Net CO2 assimilation was above zero about 30 days after leaf emergence or when the leaves were half fully expanded. Chlorophyll concentrations increased from 0.7 +/- 0.2 mg g-1 in young red leaves to 10.3 +/- 0.7 mg g-1 in dark green leaves, along with stomatal conductance (gs, from 0.16 +/- 0.09 to 0.47 +/- 0.17 mol H2O m-2 s-1). Fruit growth was sigmoidal, with maximum values of fresh mass (29 g), dry mass (6 g) and fruit surface area (39 cm2) occurring 97 to 115 days after fruit set. Fruit CO2 exchange in the light (Rl) and dark (Rd) decreased from fruit set to fruit maturity, whether expressed on a surface area (10 to 3 micromol CO2 m-2 s-1 and 20 to 3 micromol CO2 m-2 s-1, respectively) or on a dry mass basis (24 to 2 nmol CO2 g-1 s-1 and 33 to 2 nmol CO2 g-1 s-1, respectively). Photosynthesis never exceeded respiration, however, the difference between Rl and Rd was greatest in young green fruit (4 to 8 micromol CO2 m-2 s-1). About 90% of the carbon required for fruit growth was accounted for in the dry matter of the fruit, with the remainder required for respiration. Fruit photosynthesis contributed about 3% of the total carbon requirement of the fruit over the season. Fruit growth was mainly dependent on CO2 assimilation in recently expanded dark green leaves. 相似文献
11.
Whitehead D Walcroft AS Scott NA Townsend JA Trotter CM Rogers GN 《Tree physiology》2004,24(7):795-804
Responses of photosynthesis to carbon dioxide (CO2) partial pressure and irradiance were measured on leaves of 39-year-old trees of manuka (Leptospermum scoparium J. R. Forst. & G. Forst.) and kanuka (Kunzea ericoides var. ericoides (A. Rich.) J. Thompson) at a field site, and on leaves of young trees grown at three nitrogen supply rates in a nursery, to determine values for parameters in a model to estimate annual net carbon uptake. These secondary successional species belong to the same family and commonly co-occur. Mean (+/- standard error) values of the maximum rate of carboxylation (hemi-surface area basis) (Vcmax) and the maximum rate of electron transport (Jmax) at the field site were 47.3 +/- 1.9 micromol m(-2) s(-1) and 94.2 +/- 3.7 micromol m(-2) s(-1), respectively, with no significant differences between species. Both Vcmax and Jmax were positively related to leaf nitrogen concentration on a unit leaf area basis, and the slopes of these relationships did not differ significantly between species or between the trees in the field and young trees grown in the nursery. Mean values of Jmax/Vcmax measured at 20 degrees C were significantly lower (P < 0.01) for trees in the field (2.00 +/- 0.05) than for young trees in the nursery with similar leaf nitrogen concentrations (2.32 +/- 0.08). Stomatal conductance decreased sharply with increasing air saturation deficit, but the sensitivity of the response did not differ between species. These data were used to derive parameters for a coupled photosynthesis-stomatal conductance model to scale estimates of photosynthesis from leaves to the canopy, incorporating leaf respiration at night, site energy and water balances, to estimate net canopy carbon uptake. Over the course of a year, 76% of incident irradiance (400-700 nm) was absorbed by the canopy, annual net photosynthesis per unit ground area was 164.5 mol m(-2) (equivalent to 1.97 kg C m(-2)) and respiration loss from leaves at night was 37.5 mol m(-2) (equivalent to 0.45 kg m(-2)), or 23% of net carbon uptake. When modeled annual net carbon uptake for the trees was combined with annual respiration from the soil surface, estimated net primary productivity for the ecosystem (0.30 kg C m(-2)) was reasonably close to the annual estimate obtained from independent mensurational and biomass measurements made at the site (0.22 +/- 0.03 kg C m(-2)). The mean annual value for light-use efficiency calculated from the ratio of net carbon uptake (net photosynthesis minus respiration of leaves at night) and absorbed irradiance was 13.0 mmol C mol(-1) (equivalent to 0.72 kg C GJ(-1)). This is low compared with values reported for other temperate forests, but is consistent with limitations to photosynthesis in the canopy attributable mainly to low nitrogen availability and associated low leaf area index. 相似文献
12.
Effects of photosynthetic photon flux density (PPFD) on leaf gas exchange of lychee (Litchi chinensis Sonn.) were studied in field-grown "Kwai May Pink" and "Salathiel" orchard trees and young potted "Kwai May Pink" plants during summer in subtropical Queensland (27 degrees S). Variations in PPFD were achieved by shading the trees or plants 1 h before measurement at 0800 h. In a second experiment, potted seedlings of "Kwai May Pink" were grown in a heated greenhouse in 20% of full sun (equivalent to maximum noon PPFD of 200 micromol m(-2)xs(-1)) and their growth over three flush cycles was compared with seedlings grown in full sun (1080 micromol m(-2)xs(-1)). Young potted plants of "Kwai May Pink" were also grown outdoors in artificial shade that provided 20, 40, 70 or 100% of full sun (equivalent to maximum PPFDs of 500, 900, 1400 and 2000 micromol m(-2)xs(-1)) and measured for shoot extension and leaf area development over one flush cycle. Net CO2 assimilation increased asymptotically in response to increasing PPFD in both orchard trees and young potted plants. Maximum rates of CO2 assimilation (11.9 +/- 0.5 versus 6.3 +/- 0.2 micromol CO2 m(-2) s(-1)), dark respiration (1.7 +/- 0.3 versus 0.6 +/- 0.2 micromol CO2 m(-2) s(-1)), quantum yield (0.042 +/- 0.005 versus 0.027 +/- 0.003 mol CO2 mol(-1)) and light saturation point (1155 versus 959 micromol m(-2) s(-1)) were higher in orchard trees than in young potted plants. In potted seedlings grown in a heated greenhouse, shoots and leaves exposed to full sun expanded in a sigmoidal pattern to 69 +/- 12 mm and 497 +/- 105 cm(2) for each flush, compared with 27 +/- 7 mm and 189 +/- 88 cm(2) in shaded seedlings. Shaded seedlings were smaller and had higher shoot:root ratios (3.7 versus 3.1) than seedlings grown in full sun. In the potted plants grown outdoors in 20, 40, 70 or 100% of full sun, final leaf area per shoot was 44 +/- 1, 143 +/- 3, 251 +/- 7 and 362 +/- 8 cm(2), respectively. Shoots were also shorter in plants grown in shade than in plants grown in full sun (66 +/- 5 mm versus 101 +/- 2 mm). Photosynthesis in individual leaves of lychee appeared to be saturated at about half full sun, whereas maximum leaf expansion occurred at higher PPFDs. We conclude that lychee plants can persist as seedlings on the forest floor, but require high PPFDs for optimum growth. 相似文献
13.
When the exotic Acer platanoides L. (Norway maple) and the native A. saccharum Marsh. (sugar maple) grow together in the understories of urban Quercus forests in the eastern USA, average annual height growth increments are nearly twice as large in A. platanoides as in A. saccharum, 19.26 +/- 3.22 versus 10.01 +/- 1.69 cm. We examined several ecophysiological mechanisms that might be associated with the superior invasive ability and growth of A. platanoides in two urban oak forests in Pennsylvania. Leaf longevity was 12 days greater in A. platanoides than in A. saccharum. In addition, leaf mass/leaf area ratio was greater in A. platanoides than in A. saccharum (2.67 +/- 0.03 versus 2.32 +/- 0.02 mg cm(-2)); however, leaf thickness was significantly lower in A. platanoides than in A. saccharum suggesting that A. platanoides contains more dense palisade and mesophyll cell layers than A. saccharum. Field net photosynthesis (mass basis) and photosynthetic light response curves (area basis) indicated significantly greater carbon assimilation, and nitrogen and phosphorus use efficiencies in A. platanoides than in A. saccharum. Acer platanoides also exhibited higher water use efficiency than A. saccharum (0.88 +/- 0.12 versus 0.32 +/- 0.09 mmol CO(2) mol(-1) H(2)O). Acer platanoides exhibited significantly lower osmotic potentials than A. saccharum, but a similar relative water content at zero turgor. We conclude that A. platanoides utilizes light, water and nutrients more efficiently than A. saccharum. 相似文献
14.
Cuttings of balsam spire hybrid poplar (Populus trichocarpa var. Hastata Henry x Populus balsamifera var. Michauxii (Dode) Farwell) were grown in sand culture and irrigated every 2 (W) or 10 (w) days with a solution containing either 3.0 (N) or 0.5 (n) mol nitrogen m(-3) for 90 days. Trees in the WN (control) and wn treatments had stable leaf nitrogen concentrations averaging 19.4 and 8.4 mg g(-1), respectively, over the course of the experiment. Trees in the Wn and wN treatments had a similar leaf nitrogen concentration, which increased from 12.0 to 15.8 mg g(-1) during the experiment. By the final harvest, mean stomatal conductances of trees in the wN and wn treatments were less than those of trees in the Wn and WN treatments (1.8 versus 4.6 mm s(-1)). Compared to the WN treatment, biomass at the final harvest was reduced by 61, 72 and 75% in the Wn, wN and wn treatments, respectively. At the final harvest, WN trees had a mean total leaf area of 4750 +/- 380 cm(2) tree(-1) and carried 164 +/- 8 leaves tree(-1) with a specific leaf area of 181 +/- 16 cm(2) g(-1), whereas Wn trees had a smaller mean total leaf area (1310 +/- 30 cm(2) tree(-1)), because of the production of fewer leaves (41 +/- 6) with a smaller specific leaf area (154 +/- 2 cm(2) g(-1)). A greater proportion of biomass was allocated to roots in Wn trees than in WN trees, but component nitrogen concentrations adjusted such that there was no Wn treatment effect on nitrogen allocation. Compared with WN trees, rates of photosynthesis and respiration per unit weight of tissue of Wn trees decreased by 28 and 31%, respectively, but the rate of photosynthesis per unit leaf nitrogen remained unaltered. The wN and Wn trees had similar leaf nitrogen concentrations; however, compared with the Wn treatment, the wN treatment decreased mean total leaf area (750 +/- 50 cm(2) tree(-1)), number of leaves per tree (29 +/- 2) and specific leaf area (140 +/- 6 cm(2) g(-1)), but increased the allocation of biomass and nitrogen to roots. Net photosynthetic rate per unit leaf nitrogen was 45% lower in the wN treatment than in the other treatments. Rates of net photosynthesis and respiration per unit weight of tissue were 48 and 33% less, respectively, in wN trees than in Wn trees. 相似文献
15.
Foliar herbivory and leaf traits of five native tree species in a young plantation of Central Panama
Gillian S. Paul Florencia Montagnini Graeme P. Berlyn Dylan J. Craven Michiel van Breugel Jefferson S. Hall 《New Forests》2012,43(1):69-87
This study examined foliar herbivory on 1 year-old tree saplings planted in previously abandoned fields in central Panama.
Plots (15 × 15 trees) of Anacardium excelsum (Anacardiaceae), Dalbergia retusa (Fabaceae), Pachira quinata (Malvaceae), Tabebuia rosea (Bignoniaceae), and Terminalia amazonia (Combretaceae) were tested for herbivory using leaf counts and digital image analysis. Values of foliar carbon, foliar nitrogen,
specific leaf area (SLA), and leaf toughness were analyzed to describe mechanical defenses and leaf nutrients on young and
mature leaves of each of these species. For all five species, less than 10% of total leaf area was found to be damaged by
arthropods. Significant (P-value < 0.001) differences in herbivory were found among both the tree species and the insect feeding guilds considered:
chewing, skeletonizing, mining, and leaf-rolling. On mature leaves, Anacardium excelsum had the highest amount of leaf damage (3.53%) while Dalbergia retusa exhibited the lowest herbivore damage (1.72%). Tabebuia rosea had statistically significantly higher damage than other species for young leaves caused by leaf-rolling insects (4.21% rolling
of 5.55% total damage). Leaf toughness was negatively correlated with SLA and foliar N. Linear regressions showed that herbivory
was positively correlated with foliar N for young leaves and negatively correlated with foliar N for mature leaves. No statistically
significant relationships were found between herbivory and the mechanical properties of toughness and SLA. Overall, results
from this study indicate that, as young saplings, the species evaluated did not suffer high amounts of foliar herbivory in
the plantation environment. 相似文献
16.
《林业研究》2016,(3)
We evaluated the phenology and litterfall dynamics of the mangrove Bruguiera gymnorrhiza(L.)Lamk along the Okukubi River, Okinawa Island, Japan.Over 3 years, this species showed the highest litterfall of leaves and stipules in summer and the lowest litterfall in winter. From Kendall's coefficient of concordance, the monthly changes in leaf, stipule, and branch were strongly and significantly concordant among years. Leaf and stipule litterfall could be governed by monthly maximum wind speed, monthly day length, and monthly mean air temperature. Branch litterfall depended on monthly maximum wind speed and monthly rainfall, and increased exponentially with increasing monthly maximum wind speed. Mean total litterfall was 11.8 Mg ha~(-1)yr~(-1), with the largest component being leaf litterfall(65.8 %). Annual leaf litterfall per plot was almost constant regardless of the tree density of the plot. Mean leaf longevity was 18 months.Flower and mature propagule litterfall might be influenced by monthly mean air temperature, monthly day length and monthly mean air temperature. The average development periods from flower buds to flowers and flower buds to mature propagules were 1 and 8 months, respectively.Except for leaf and branch, all vegetative and reproductive organ litterfall had clear annual cycles. B. gymnorrhiza showed a positive correlation between leaf production and reproductive organ production. 相似文献
17.
Liakopoulos G Stavrianakou S Filippou M Fasseas C Tsadilas C Drossopoulos I Karabourniotis G 《Tree physiology》2005,25(2):157-165
For plant species in which a considerable portion of the photoassimilates are translocated in the phloem as sugar alcohols, boron is freely translocated from mature organs to growing tissues. However, the effects of decreased plant boron status on boron remobilization are poorly understood. We conducted a growth chamber experiment (CE) and a field experiment (FE) to study the effects of low boron supply on boron remobilization in olive (Olea europaea L.), a species that transports considerable amounts of mannitol in the phloem. For the CE, several physiological parameters were compared between control (B+) and boron-deficient olive plants (B-) during the expansion of new leaves. Boron remobilization was assessed by measuring boron content of selected leaves at the beginning and at the end of the CE. As expected, boron was remobilized from mature leaves to young leaves of B+ plants; however, considerable boron remobilization was also observed in B- plants, suggesting a mechanism whereby olive can sustain a minimum boron supply for growth of new tissues despite an insufficient external boron supply. Boron deficiency caused inhibition of new growth but had no effect on photosynthetic capacity per unit leaf surface area of young and mature leaves, thereby altering the carbon utilization pattern and resulting in carbon allocation to structures within the source leaves and accumulation of soluble carbohydrates. Specifically, in mature B- leaves in the CE and in B- leaves in the FE, mannitol concentration on a leaf water content basis increased by 48 and 27% respectively, compared with controls. Carbon export ability (assessed by both phloem anatomy and phloem exudate composition of FE leaves) was enhanced at low boron supply. We conclude that, at low boron supply, increased mannitol concentrations maintain boron remobilization from source leaves to boron-demanding sink leaves. 相似文献
18.
Prunus ferganensis (Kost. & Riab) Kov. & Kost, a close relative of cultivated peach (Prunus persica (L.) Batsch.), is native to arid regions of central Asia. A distinguishing feature of P. ferganensis is its prominent, elongated, unbranched pattern of leaf venation. To determine whether the long-vein trait could be used as a marker in breeding for drought tolerance, we investigated the association between this trait and the leaf morphological and physiological parameters related to drought response in P. ferganensis, P. persica and two interspecific hybrids, one with the long-vein trait (BY94P7585) and one without (BY94P7589). The four genotypes were grafted onto "Guardian" peach rootstock and half of the plants were assigned to a drought treatment in which irrigation was limited to 25-50% of the evapotranspiration (ET) rate measured in the remaining well-watered plants, which were irrigated to runoff daily. The drought treatment reduced photosynthesis and leaf conductance by 49-83% and reduced total leaf area per plant by 17-24%, but generally did not affect mid-morning leaf water potential. Leaf gas exchange did not differ among genotypes in either treatment. Sorbitol accumulated in mature leaves in response to drought, but neither its amount nor its metabolism varied systematically with climatic adaptation among genotypes. Accumulation of transport sugars was highest in P. ferganensis, indicating that growth reduction may represent an important strategy for coping with drought in this species. Prunus ferganensis and the hybrids had higher ET than P. persica, and seemed to use water opportunistically, maintaining high gas exchange rates and consequently high ET when water was available, and avoiding low water potentials through stomatal closure as soil water declined. Leaf size (cm(2) leaf(-1)) and specific leaf area (cm(2) g(-1) dry mass) were lower in P. ferganensis and the hybrids than in P. persica. We conclude that the long-vein trait is not a reliable marker for drought tolerance, but leaf traits of P. ferganensis such as size and specific leaf area may be useful in P. persica breeding programs targeting drought tolerance. 相似文献
19.
Sunlight interception efficiency was compared at the leaf, shoot, branch and crown levels for Picea engelmannii (Parry) and Abies lasiocarpa ((Hook.) Nutt.), dominant tree species of the central Rocky Mountains, USA. The ratio of silhouette to total leaf area (STAR) was used to quantify the efficiency of direct-beam sunlight interception at each structural scale. Total mean reductions in STAR from the leaf to the crown level were 0.39 to 0.06 in P. engelmannii and 0.46 to 0.02 in A. lasiocarpa. These reductions in STAR occurred for both species as structural scale increased due to a more upright leaf inclination, increased leaf twisting and curvature, or greater mutual shading among plant structures. A steeper leaf inclination between the leaf and shoot level accounted for 26 +/- 19% (95% C.I.) of the total leaf-to-crown STAR reduction; mutual shading among leaves on shoots caused a 14 +/- 7% reduction, whereas leaf curvature and twisting accounted for 22 +/- 3% for a total reduction of 62 +/- 8%. The STAR varied slightly from the shoot to the branch level (+/- 7%) except for a 26% reduction in shade shoots of A. lasiocarpa as a result of increased mutual shading among leaves at lateral nodes. Another substantial reduction in STAR occurred from the branch to the crown level (35 +/- 3% of total) as a result of shading of one branch layer by another within the crown. Thus, light interception efficiency decreased as structural scale increased in both species, especially from the leaf to the shoot level and from the branch to the crown level. 相似文献
20.
In the alpine timberline ecotone at 1350 m in the CraigieburnRange, New Zealand, four distinct mountain beech stand types(a pole, a coppice, a high forest and a shrublike stand) wereanalysed for stand biomass and leaf area by means of allomet-ricregressions based on stem diameter. Differences between stand types in terms of age, structure,biomass and leaf area are interpreted as development stagesafter stand breakdowns due to external impacts. Vegetative reproduction,mainly coppicing, plays an important part in stand regeneration. The young pole stand had 177 t ha–1, the coppice stand272 t ha–1, and the mature high forest stand 323 t ha–1aboveground dry weight. A low mountain beech shrub stand withgnarled, windshaped dwarf trees had only 135 t ha–1. Foliageaccounted for only 3–5% in all stands, the leaf area indexwas also low, at 3.0 in the shrub stand and 3.7–7.4 inthe forest stands. The low foliage proportion is consideredto be a response to the harsh environment. 相似文献