共查询到20条相似文献，搜索用时 45 毫秒
1.
About 95% of swamp tupelo (Nyssa sylvatica var. biflora (Walt.) Sarg.) and sweetgum (Liquidambar styraciflua L.) seedlings survived continuous root flooding for more than two years, whereas none of the swamp chestnut oak (Quercus michauxii Nutt.) and cherrybark oak (Q. falcata var. pagodifolia Ell.) seedlings survived one year of flooding. Death of oak seedlings occurred in phases associated with periods of major vegetative growth, e.g., after bud burst in spring, after summer stem elongation, and during the winter deciduous stage, suggesting that stored reserves and sources were inadequate to maintain the seedlings when vegetative sinks were forming. Additional evidence that flooding induced a source deficiency in oak was that leaves of flooded oak were 65 to 75% smaller than leaves of nonflooded oak. Flooded swamp tupelo seedlings had a normal leaf size and patchy stomatal opening compared with nonflooded seedlings. Flooding caused increases in alcohol dehydrogenase (ADH) specific activity in taproot cambial tissues and increases in starch concentrations of swamp tupelo seedlings that were reversed when seedlings were removed from flooding. Flooding had little effect on soluble sugar concentrations in swamp tupelo or sweetgum. In the long-term flood-dry-flood treatment, in which all species had survivors, upper canopy leaf photosynthetic rates were higher in all species during the dry period than in nonflooded controls, whereas their starch and soluble sugars concentrations were similar to those of nonflooded controls. Based on seedling survival and the sink-source relationships, the order of flood tolerance was: swamp tupelo > sweetgum > swamp chestnut oak > cherrybark oak. 相似文献
2.
Brian Roy Lockhart Emile S. Gardiner John D. Hodges Andrew W. Ezell 《Annals of Forest Science》2008,65(8):801-801
- ? Continued problems in regenerating oak forests has led to a need for more basic information on oak seedling biology.
- ? In the present study, carbon allocation and morphology were compared between cherrybark oak (Quercus pagoda Raf.) seedlings and sprouts at 1-Lag grown in full, 47%, and 20% sunlight.
- ? Results indicated that cherrybark oak seedling carbon allocation and morphology responded plastically to light availability. In full light, roots were sinks for 14C, while shoots were sinks for 14C under reduced light availability. Cherrybark oak sprouts exhibited similar carbon allocation patterns in response to light availability, but displayed stronger shoot sinks than seedlings when grown underreduced light availability. We also showed that young oak sprout roots are a sink for 14C-photosynthates.
- ? Results from this study point to the need for a morphological index for oak sprout development so more precise comparisons in sprout development and physiology can be made with seedlings.
3.
Two-year-old cherrybark oak (Quercus pagoda Raf.) seedlings raised in full or partial (27%) sunlight were flooded for 30 days to study the effects of light availability and root inundation on photosynthetic light response. Compared with seedlings receiving full sunlight, seedlings receiving partial sunlight developed leaves with 90% greater blade area, 26% less mass per unit volume, and 35% lower nitrogen (N) concentration per unit area, leading to a 15% reduction in leaf photosynthetic capacity when carbon exchange rates were based on blade area. However, when carbon exchange rates were based on leaf mass, leaves acclimated to partial sunlight exhibited a 15% greater photosynthetic capacity realized primarily through an increased initial slope of the photosynthetic light response (A/PPFD) curve and increased net photosynthesis at leaf saturation (Amax). Short-term flooding increased leaf mass per unit area more than 19%, reduced foliar N concentrations per unit dry mass by 19%, and initiated reductions in Amax and apparent quantum yield (phi) of seedlings in both light regimes. Greatest impairment of Amax (56% area basis, 65% mass basis) and phi (40%) were observed in leaves receiving full sunlight, and the declines were concomitant with a 35% decrease in chlorophyll concentration. Flooding also depressed instantaneous photosynthetic N-use efficiency (PPNUE) such that Amax decreased 54%, and the initial slope of PPNUE/PPFD curves decreased 33 and 50% for leaves acclimated to partial and full sunlight, respectively. The A/PPFD patterns indicated that the magnitude of flood-induced inhibition of the photosynthetic mechanism of cherrybark oak seedlings is determined partly by the light environment. 相似文献
4.
Patterns of carbon allocation in northern red oak (Quercus rubra L.), characterized by episodic growth through recurrent single-season flushing, vary by growth stage. To examine post-transplant timing and carbohydrate sources for new root growth, dormant, bare-root, half-sibling northern red oak seedlings were transplanted to pots and placed in a favorable growth chamber environment. Unlabeled seedlings were harvested at transplant and at the bud swell stage. After leaf emergence, seedlings were exposed to (14)CO(2) at the linear shoot, linear leaf or lag growth stages. Seedlings were then placed in a growth room for 48 h to allow for translocation of (14)C-labeled current photosynthate and its stabilization in sink component plant parts. Seedlings were subsequently harvested and tissue (14)C:(12)C ratio analyzed. New root growth began during the linear shoot growth stage. However, no increase in (14)C:(12)C ratio was found in new roots until the linear leaf and lag growth stages, indicating a downward shift in translocation of current photosynthate to fuel new root growth. In old roots, (14)C:(12)C ratio increased at the lag stage. Our results indicate that both stored carbohydrates and current photosynthate contribute to new root growth of transplanted northern red oak seedlings; stored carbohydrates promote initial new root proliferation, whereas current photosynthate assumes a greater role as new leaves mature and the flush terminates. Optimizing nursery practices to increase carbohydrate reserves may reduce the time required to establish root-soil contact and facilitate early post-planting survival. 相似文献
5.
【目的】解析光合产物在马尾松幼苗植株中的运输和分配规律,揭示马尾松生产力形成过程,为探讨不同环境干扰下马尾松光合产物分配过程的变化提供参考依据。【方法】采用 13 C同位素脉冲标记法,对1.5年生马尾松幼苗进行标记,标记结束后第0、2、5、17、24、72、120、168、216和 360 h ,按不同部位对马尾松幼苗进行全收获取样,测定 13 C含量,以监测近期合成的光合产物在马尾松幼苗中的运输和分配规律,同时测定光合产物全碳、非结构性碳水化合物(NSC)在各个器官的积累量。【结果】1)标记的光合产物在针叶中合成后,向各库器官的运输量随着时间延长由多逐渐减少,具体表现为标记结束后0~24 h内最多,24~216 h逐渐减少,216 h之后运输完成,且59%以上标记的光合产物在0~24 h内运输到各库器官。2)光合产物运输趋于稳定后,在各器官的分配大小依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝,与生物量的分配大小一致,但与库活力大小不同,其库活力依次为当年生叶>当年生枝>1年生叶>根>1年生枝>茎干。3)各器官全碳和NSC积累量的分配与近期合成光合产物的分配大小一致,依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝。【结论】马尾松幼苗光合产物运输速率大于0.1 m ·h -1 ,59%以上标记的光合产物在合成后的0~ 24 h 内完成向各个库器官输出。新合成的光合产物在各器官中的积累量表现为功能器官(叶和根)居多,这一分配规律有利于马尾松幼苗阶段的生长。 相似文献
6.
K. Francis Salifu Kent G. Apostol Douglass F. Jacobs M. Anisul Islam 《Annals of Forest Science》2008,65(1):101-101
We evaluated gas exchange, chlorophyll index (CI) using SPAD-502 chlorophyll meter, and leaf nutritional responses in one-year-old northern red oak (Quercus rubra L.) container seedlings transplanted into control (unfertilized) or fertilized (0.86 g N plant?1) sand culture and grown in a greenhouse for 90 days. We labeled current nitrogen (N) uptake with (15NH4)2SO4 and directly quantified proportional contributions of N derived from fertilizer (NF) compared with retranslocation or N derived from plant (NP) in leaf growth of red oak seedlings. NF met a greater N demand in leaf growth of fertilized plants while unfertilized seedlings relied entirely on NP for their leaf growth. Fertilization increased leaf dry mass by 67% and new stem dry mass by 253% 90 days after transplanting compared to control seedlings. Specific leaf area (SLA) was not significantly altered but CI increased 90 days after transplanting. Higher leaf N concentration and content in fertilized compared with control seedlings was linked to greater chlorophyll concentrations in the former plants. The higher coefficient of determination (r 2 = 0.72) noted between leaf N concentrations and CI suggests that the SPAD meter could be a useful tool for assessing leaf N status in northern red oak seedlings. Fertilized seedlings exhibited higher net assimilation, stomatal conductance, and transpiration rates compared with controls. Increased seedling growth in response to fertilization was related to maintenance of higher gas exchange and greater nutrient uptake, which could improve outplanting success. 相似文献
7.
CHENG Song 《中国林学(英文版)》2009,11(2):65-76
The relationships between plant organs and root hydrological traits are not well known and the question arises whether elevated CO2 changes these relationships. This study attempted to answer this question. A pseudo-replicated experiment was conducted with two times 24 American elm (Ulmus americana L.) and 23 and 24 red oak (Quercus rubra L.) seedlings growing in ambient CO2 (around 360 μmol·L–1) and 540 ± 7.95 μmol·L–1 CO2 in a greenhouse. After 71 days of treatment for American elm and 77 days for red oak, 14 American elm and 12 red oak seedlings from each of the two CO2 levels were randomly selected in order to examine the flow rate of root xylem sap, root hydraulic conductance, total root hydraulic conductivity, fine root and coarse root hydraulic conductivity. All seedlings were harvested to investigate total plant biomass, stem biomass and leaf biomass, leaf area, height, basal diameter, total root biomass, coarse root biomass and fine root biomass. The following conclusions are reached: 1) plant organs respond to the elevated CO2 level earlier than hydraulic traits of roots and may gradually lead to changes in hydraulic traits; 2) plant organs have different relationships with hydraulic traits of roots and elevated CO2 changes these relationships; the changes may be of importance for plants as means to acclimatize to changing environments; 3) biomass of coarse roots increased rather more than that of fine roots; 4) Lorentzian and Caussian models are better in estimating the biomass of seedlings than single-variable models. 相似文献
8.
Despite the general practice of root pruning, little is known about the potential impact of reducing shoot/root systems of oak seedlings in this way on their future susceptibility to pathogens, for example Cylindrocarpon spp., Fusarium spp., Ilyonectria spp., Pythium spp. Phytophthora spp. or Rhizoctonia spp. In this study, root‐pruned and non‐pruned seedlings of Quercus robur grown under controlled conditions were inoculated with aggressive and less‐aggressive pathogens. Results indicated, in contrast to our initial assumption, that pathogens significantly reduced lateral root biomass more in non‐pruned seedlings, the extent of the response depending on the pathogens species. In response to pathogen pressure, pruned seedlings tended to attain a higher dry stem mass fraction, but lower dry leaf mass fraction. Pathogens also suppressed leaf mass in total root dry mass fraction (dry leaf mass/total root dry mass ratio, in g × g?1) more in pruned than in non‐pruned seedlings. These results suggest differences in growth between non‐pruned and pruned seedlings in response to pathogen stress. In nurseries, root pruning of oak trees may enhance the reduction in leaf mass in lateral roots mass fraction resulting from pathogen infections, which may decrease seedling quality. It is therefore important to ensure a low level of inoculum of soil‐borne pathogens to minimize the risk of seedling infection. 相似文献
9.
10.
A field experiment was established in a second-growth hardwood forest dominated by red oak (Quercus rubra L.) to examine the effects of shelterwood overstory density on leaf gas exchange and seedling water status of planted red oak, naturally regenerated red oak and sugar maple (Acer saccharum Marsh.) seedlings during the first growing season following harvest. Canopy cover of uncut control stands and moderate and light shelterwoods averaged 97, 80 and 49%, respectively. Understory light and vapor pressure deficit (VPD) strongly influenced gas exchange responses to overstory reduction. Increased irradiance beneath the shelterwoods significantly increased net photosynthesis (P(n)) and leaf conductance to water vapor (G(wv)) of red oak and maple seedlings; however, P(n) and G(wv) of planted and naturally regenerated red oak seedlings were two to three times higher than those of sugar maple seedlings in both partial harvest treatments, due in large part to decreased stomatal limitation of gas exchange in red oak as a result of increased VPD in the shelterwoods. In both species, seedling water status was higher in the partial harvest treatments, as reflected by the higher predawn leaf water potential and seedling water-use efficiency in seedlings in shelterwoods than in uncut stands. Within a treatment, planted and natural red oak seedlings exhibited similar leaf gas exchange rates and water status, indicating little adverse physiological effect of transplanting. We conclude that the use of shelterwoods favors photosynthetic potential of red oak over sugar maple, and should improve red oak regeneration in Ontario. 相似文献
11.
We initiated a study on a bottomland site in the southern United States to examine the effects of Japanese honeysuckle (Lonicera japonica Thunberg) control and seedlings of two root classes on survival and growth of underplanted cherrybark oak (Quercus pagoda Raf.) seedlings. Three honeysuckle control treatments were assigned to nine 0.5-ha plots in a stand harvested to 30% residual stocking. Treatments included a spring 1997 herbicide application (Escort®, metsulfuron-methyl), a similar application in the late summer of 1997, and a control (no herbicide application). In 1998, half of each treatment plot was planted with seedlings having four or more first-order lateral roots > 1 mm in diameter, while the other half of each plot received seedlings with fewer than four lateral roots. Four years after treatment, the early season application reduced honeysuckle biomass 60% relative to the other treatments, but we did not observe a survival or growth response by underplanted seedlings. Three years after establishment, seedlings that initially had four or more lateral roots were 16% taller and 18% larger in root-collar diameter than seedlings in the other class, but these differences were primarily due to initial size differences maintained through the study period. Over all treatments, oak seedlings averaged 87% survival while showing a 300% increase in height and a 170% increase in root-collar diameter 3 years after planting. Our results suggest that partial stand harvesting followed by underplanting may be a viable approach for establishing cherrybark oak reproduction on bottomland sites of the southern United States. 相似文献
12.
One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites. 相似文献
13.
《Forest Ecology and Management》2001,145(3):243-253
Seedlings of yellow birch originating from the same seed source were treated with two levels of fertilizers during two growing seasons. The lower level of fertilizers, such as 50 (11:41:08 N:P:K ratio), 100 (20:08:20) and 35 ppm of nitrogen (08:20:30) were applied as the starter, grower and finisher, respectively. The higher level ones consisted of 75, 150, and 100 ppm of nitrogen in the same fertilizers. After 2 years growth, seedlings treated with the higher level of fertilizers, had fewer lateral branches, greater height and larger stem diameter. After natural hardening from November to February, seedlings were subjected to 0, 5, 10, 19 and 27 days of a simulated winter thaw followed by 10 weeks at −10°C. After the thaw-refreeze treatments, series of measurements were carried out. Stem xylem cavitation and root freezing injury significantly increased with thaw duration regardless of levels of fertilizer treatments. Stem freezing injury also significantly increased with thaw duration in all stem segments of seedlings treated with the higher level of fertilizers, but only in the top segments for the seedlings provided with the lower level of fertilizers. However, seedlings treated with the higher level of fertilizers developed cavitation more quickly. After 1 month of growth in the greenhouse following the thaw and freeze treatment, both types of seedlings showed significant decrease in the length of new shoot growth and increase in percent length of shoot dieback with thaw duration. The length of new shoots, however, was always greater for the plants treated with the higher level of fertilizers. No difference of shoot dieback between the seedlings of the two different nursery treatments were observed. Correlation analyses showed that the length of new shoots was highly related to root and stem freezing injury, while dieback was best correlated with root freezing injury and stem xylem cavitation regardless of the levels of fertilizer treatments. It was concluded that (1) the higher level of fertilizer applied during the culture of yellow birch seedlings can accelerate xylem cavitation and dehardening in the stem following freeze–thaw events; (2) stem xylem cavitation was unlikely the cause of stem freezing injury; and (3) root freezing injury and stem xylem cavitation are the most reliable measurements for predicting dieback of potential planting stock, but both root and shoot freezing injury are relate well to regrowth of new shoots in stock exposed to prolonged thaw. 相似文献
14.
Northern red oak (Quercus rubra L.) seedlings and trees differ in their response to ozone. Previous work reported reductions in net photosynthesis, carboxylation efficiency and quantum yield of mature tree leaves, whereas seedling processes were unaffected by the same ozone exposure. To further characterize differences in ozone response between seedlings and mature trees, we examined carbon partitioning and allocation in 32-year-old trees and 4-year-old seedlings of northern red oak after exposure to subambient (seasonal SUM00 dose (sum of all hourly ozone exposures) = 31 ppm-h), ambient (SUM00 dose = 85 ppm-h) and twice ambient (SUM00 dose = 151 ppm-h) ozone concentrations for three growing seasons. For mature trees, ozone exposure decreased foliar starch partitioning, increased starch partitioning in branches and increased (14)C retention in leaves. In contrast, starch partitioning in leaves and branches, and foliar (14)C retention in seedlings were unaffected by ozone exposure, but soluble carbohydrate concentrations in coarse and fine roots of seedlings were reduced. Differences in carbohydrate demand between seedlings and mature trees may underlie the higher leaf ozone uptake rates and greater physiological response to ozone in mature northern red oak trees compared with seedlings. 相似文献
15.
Leaf conductance, water relations, growth, and abscisic acid (ABA) concentrations in xylem sap, root apices and leaves were assessed in oak seedlings (Quercus robur L.) grown with a root system divided between two compartments and subjected to one of four treatments: (a) well watered, WW; (b) half of root system exposed to soil drying and half kept well watered, WD; (c) whole root system exposed to drought, DD; and (d) half of root system severed, RE. Sharp decreases in plant stomatal conductance, leaf water potential, hydraulic conductance and leaf growth were observed during DD treatment. No significant differences in plant leaf water potential and stomatal conductance were detected between the WW and WD treatments. Nevertheless, the WD treatment resulted in inhibition of leaf expansion and stimulation of root elongation only in the well-watered compartment. Abscisic acid concentrations did not change in leaves, root tips, or xylem sap of WD- compared to WW-treated plants. Increased concentrations of ABA were observed in xylem sap from DD-treated plant roots, but the total flux of ABA to shoots was reduced compared to that in WW-treated plants, because of decreases in transpiration flux. Similar plant responses to the WD and RE treatments indicate that the responses observed in the WD-treated plants were probably not triggered by a positive signal originating from drying roots. 相似文献
16.
采用盆栽沙培法,研究分析了0、50、100、175mg/kg4种不同氮营养供给水平对美丽胡枝子(Lespedeza formosa)幼苗生长和其体内氮、磷二种养分浓度变化的影响。结果表明,施加0～100mg/kg氮对幼苗株高、地上和地下部分的生长都有促进作用,但超过100mg/kg氮时,过量供氮对幼苗的生长产生抑制作用;氮供给不足时,幼苗表现出将更多的生物量分配到根系,根冠比大;幼苗根和茎叶中的氮浓度随供氮水平的增加而增加。在供氮为0～50mg/kg时,幼苗根和茎叶中的磷浓度随氮浓度的增加稍有下降,当供氮浓度在50～100mg/kg时,根和茎叶中磷浓度随氮浓度的增加而升高,当氮浓度超过100mg/kg时,其根和茎叶中的磷浓度随氮浓度的增加而呈下降趋势。 相似文献
17.
We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. Defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also exerted a significant inhibitory effect. Removal of mature leaves had only a minor effect on root suckering. Removal of a continuous band of bark (girdling) at the base of the stem consistently stimulated growth of adventitious shoots from the stem below the girdle and occasionally promoted root suckering. Exogenous application of indole-3-acetic acid to excised stumps inhibited root suckering and basal stem sprouting. Naphthylphthalamic acid (NPA), an auxin polar transport inhibitor, had no effect on root suckering or stem sprouting when it was applied to the bark of the basal stem. However, NPA significantly increased root suckering when it was applied to the exposed surface of xylem after girdling. These results suggest that polar transport of auxin in the xylem parenchyma is an important inhibitor of root suckering. On decapitated stems, vacuum extraction of xylem sap from the root system lowered the frequency of root suckering compared with decapitation alone, indicating that substance(s) originating in the root system also play a significant role in controlling root suckering. 相似文献
18.
D. S. Thomas 《New Forests》2009,38(3):245-259
Forestry requires low mortality of transplanted seedlings. Mortality shortly after planting is often associated with inadequate
hydration of transplants. Seedlings can be hardened to the drought conditions they may experience after transplanting by exposing
them to controlled drought conditions in the nursery. Eucalyptus pilularis Sm. seedlings were drought hardened by providing nil (severe treatment) or half (mild treatment) the daily irrigation routinely
received (control treatment) for up to two non-consecutive days per week during the last 4 weeks of growth in the nursery.
Drought hardening reduced stem diameter, seedling leaf area, leaf area per root biomass and seedling quality measured by the
Dickson quality index, but increased root:shoot ratio. Hardened seedlings had lower stomatal conductance and leaf water potential
on the days they received less irrigation that the control treatment. Hardened seedlings had greater stomatal conductance
and were less water stressed than seedlings experiencing drought for the first time indicating hardened seedlings had adjusted
physiologically to drought. Survival after transplanting in the controlled drought environment in a glasshouse was enhanced
by the hardening treatments. Non hardened seedlings that had had their upper leaves manually removed immediately prior to
transplanting to reduce leaf area (top-clipped) had similar survival to hardened seedlings. Stomatal conductance and leaf
water potential after transplanting were higher in hardened and top-clipped seedlings than unhardened control seedlings or
vegetative cuttings. Survival in the field trial was over 95% for all treatments, possibly as rain fell within 4 days of planting
and follow-up rain occurred in the subsequent weeks. Neither the hardened or top-clipped seedlings planted in the field trial
had reduced growth, increased propensity to form double leaders or worse stem form than control seedlings when measured at
age 3 years. 相似文献
19.
Yellow birch seedlings (Betula alleghaniensis Britt.) that had lost more than 90% of their stem hydraulic conductivity during ambient winter temperatures were exposed to 0 and 20 days of a simulated winter thaw followed by a 48-h freezing treatment at 0, -5, -10, -20 and -30 degrees C. After measuring freezing injury to shoots and roots, the seedlings were placed in a greenhouse where recovery of xylem conductivity and new growth were measured. Shoot xylem cavitation was measured as percent loss of hydraulic conductivity. Shoot freezing injury was assessed by electrolyte leakage (EL) and root freezing injury was assessed by EL and triphenyl tetrazolium chloride reduction. Seedlings pretreated with thaw had higher stem water contents and suffered more freezing damage to roots and shoots (at -20 and -30 degrees C, respectively) than unthawed seedlings. After 3 weeks in a greenhouse, seedlings from the 0, -5 and -10 degrees C freezing treatments showed complete recovery of xylem conductivity, with substantially increased stem water contents. Poor recovery of hydraulic conductivity was observed only in seedlings that were subjected to freezing treatments at -20 and -30 degrees C, regardless of thaw treatment. Of these embolized seedlings, however, only those not previously thawed showed recovery of hydraulic conductivity or regained stem water content after 9 weeks in the greenhouse. Shoot dieback, bud burst and length of new shoots were significantly related to the extent of stem xylem cavitation and freezing injury. We conclude that (1) the simulated winter thaw predisposed yellow birch seedlings to freezing damage in shoots and roots by dehardening tissues and increasing their water content; (2) root freezing damage in turn affected the seedlings' ability to refill embolized stem xylem, resulting in considerable residual xylem embolism after spring refilling; (3) further recovery of stem xylem conductivity was attributable to growth of new vessels; (4) and the permanent residual embolism, together with root and shoot freezing injury, caused increased dieback, bud mortality and reduced growth of new shoots. 相似文献
20.
Enrique Andivia Manuel Fernández Javier Vázquez-Piqué Reyes Alejano 《European Journal of Forest Research》2012,131(4):1091-1101
Despite evidences that Holm oak has a high plasticity and great adaptability, there is limited or contradictory knowledge of the morphological and physiological variability of this species. Holm oak has been widely used for reforestation projects in Mediterranean areas, but has frequently shown poor field performance. We hypothesized that Holm oak has inter-population differences in physiological responses to abiotic stressors that could affect reforestation success. The influence of nursery culture on the characteristics of Holm oaks from different provenances has not been explored in depth. Thus, we studied the effect of nursery autumn fertilization on morphological traits, frost tolerance, root growth potential, and nutritional status of two Spanish provenances of Holm oak, La Alcarria (a region with inland Mediterranean climate) and Sierra Morena Occidental (a region with a warm coastal Mediterranean climate). There were significant differences between the provenances in frost tolerance, biomass allocation, and leaf nutrient content, suggesting a role of genetic factors. The leaves of seedlings from La Alcarria had less visual damage at ?12°C than seedlings from the warmer provenance (45% vs. 92%). Seedlings from La Alcarria, compared to those from Sierra Morena, had higher leaf P concentration (0.17% vs. 0.15%), greater stem diameter (3.1?mm vs. 2.7?mm), lower shoot-to-root dry mass ratio (0.46 vs. 0.53), and lower slenderness (4.03 vs. 5.31). For both provenances, N autumn fertilization improved growth, root growth potential, cold hardiness, and nutritional status of seedlings. We suggest that forest reforestation programs should consider to a greater extent Holm oak provenances and their tolerances to different abiotic stressors. 相似文献