The effect of shading on photosynthesis,growth, and regrowth following defoliation for Bromus tectorum

Summary The effect of full sunlight, 60%, or 90% attenuated light on photosynthetic rate, growth, leaf morphology, dry weight allocation patterns, phenology, and tolerance to clipping was examined in the glasshouse for steppe populations of the introduced grass, Bromus tectorum. The net photosynthetic response to light for plants grown in shade was comparable to responses for plants grown in full sunlight. Plants grown in full sunlight produced more biomass, tillers and leaves, and allocated a larger proportion of their total production to roots than plants grown in shade. The accumulation of root and shoot biomass over the first two months of seedling growth was primarily responsible for the larger size at harvest of plants grown in full sunlight. Plants grown under 60% and 90% shade flowered an average of 2 and 6 weeks later, respectively, than plants grown in full sunlight. Regrowth after clipping was greater for plants grown in full sunlight compared to those grown in shade. Even a one-time clipping delayed flowering and seed maturation; the older the individual when leaf area was removed, the greater the delay in its phenology. Repeated removal of leaf area was more frequently fatal for plants in shade than in full sunlight. For plants originally grown in full sunlight, regrowth in the dark was greater than for shaded plants and was more closely correlated to non-flowering tiller number than to plant size. This correlation suggests that etiolated regrowth is more likely regulated by the number of functional meristems than by differences in the size of carbohydrate pools. Thus, shading reduces the rate of growth, number of tillers, and ability to replace leaf area lost to herbivory for B. tectorum. These responses, in turn, intensify the effect of competition and defoliation for this grass in forests. B. tectorum is largely restricted to forest gaps at least in part because of its inability to acclimate photosynthetically, the influence of shade on resource allocation, and the role of herbivory in exacerbating these effects.     

Relative importance of photosynthetic traits and allocation patterns as correlates of seedling shade tolerance of 13 tropical trees

Among 13 tropical tree species on Barro Colorado Island, species with high seedling mortality rates during the first year in shade had higher reltive growth rates (RGR) from germination to 2 months in both sun (23% full sun) and shade [2%, with and without lowered red: far red (R:FR) ratio] than shade tolerant species. Species with higher RGR in sun also had higher RGR in shade. These interspecific trends could be explained by differences in morphological traits and allocation paterns among species. Within each light regime, seedlings of shade-intolerant species had lower root: shoot ratios, higher leaf mass per unit area, and higher leaf area ratios (LAR) than shade tolerant species. In contrast, leaf gas exchange characteristics, or acclimation potential in these traits, had no relationship with seedling mortality rates in shade. In both shade tolerant and intolerant species, light saturated photosynthesis rates, dark respiration, and light compensation points were higher for sungrown seedlings than for shade-grown seedlings. Differences in R:FR ratio in shade did not affect gas exchange, allocation patterns, or growth rates of any species. Survival of young tree seedlings in shade did not depend on higher net photosynthesis or biomass accumulation rates in shade. Rather, species with higher RGR died faster in shade than species with lower RGR. This trend could be explained if survival depends on morphological characteristics likely to enhance defense against herbivores and pathogens, such as dense and tough leaves, a well-established root system, and high wood density. High construction costs for these traits, and low LAR as a consequence of these traits, should result in lower rates of whole-plant carbon gain and RGR for shade tolerant species than shade-intolerant species in shade as well as in sun.     

南亚热带森林24种乔木的种子萌发和幼苗生长

以膨胀珍珠岩为基质,在光和暗的条件下,对２４种南亚热带森林乔木的种子萌发和幼苗生长进行了研究。种子的形态和重量与种的演替阶段有关,种子的重量也与不同的种有关。不同种的萌发率差异较大,种子较大的种,萌发率较高。肉质果实的种子,开始萌发的时间较长。光和暗条件对萌发率和萌发速度无明显影响。幼苗高度和种子重量呈正相关,这一相关在光条件下比暗条件下更明显。暗条件明显地引起群落演替早期的树种的茎徒长,限制根的生长,而对演替后期种无显著的影响。幼苗地上部分和根系生物量的分配与种的演替阶段有关,也与不同的科有关。幼苗地上部分和根系生物量的分配也受光暗条件的影响,而不受种子重量的影响。根和叶的生物量分配和种在其群落演替阶段有关。幼苗的生物量与种子重量有显著的正相关。幼苗的相对生长率相差较大,在没有营养供应的生长基质中,以演替中间阶段的种的相对生长率较大。幼苗从种子的物质利用效率与种子重量呈负相关,而与种的演替阶段无明显的相关。     

Effects of moderate shade and irrigation with eutrophicated water on the nitrogen economy of Mediterranean oak seedlings

We evaluated the effects of moderate shade (43% vs. 100% of full sunlight) and irrigation with eutrophicated river water (daily vs. alternate-day watering) on growth and nitrogen economy of seedlings of three Mediterranean oak species, two evergreen (Quercus coccifera, Quercus ilex subsp. ballota) and a deciduous (Quercus faginea), grown in pots outdoors. Seedling biomass, N pool, N concentration and N losses by litter fall were measured at the beginning (March 2002) and end (November 2002) of a growing season. All species showed an increase of biomass and N pool under shade and/or high irrigation, while only Q. coccifera – from more arid regions – did the same under full sunlight and low irrigation. At the end of the experiment, biomass of the evergreens was higher in shade than in sun, and in high than in low irrigation, while Q. faginea – from more humid zones – responded to irrigation only. Shade-induced growth was accompanied by a decline in N concentration in the evergreens, but irrigation reduced N concentration only of Q. faginea. Shade, but not irrigation, reduced above-ground N loss. We conclude that both treatments differentially affected the evergreen and the deciduous oaks, probably due to differences in plant hydraulic and stomatal conductance. Although both treatments have similar effects on the growth of evergreens, they produced different effects on seedling N economy, which may have important consequences on future field seedling performance.     

杉木和木荷种子萌发及幼苗生长对光梯度的响应

光是影响种子萌发和幼苗生长的关键因素.为理解不同树种种子萌发及幼苗生长对光梯度变化的响应机制,本文研究了不同光照强度(分别为自然光强的100%、60%、40%、15%和5%)对杉木和木荷种子萌发及幼苗生长的影响,探讨了两树种种子萌发和幼苗生长对光照响应的差异性.结果表明: 光照强度对两树种的种子萌发和幼苗生长均具有显著影响. 随着光照强度的减弱, 杉木种子萌发率增大,萌发指数增大,木荷种子萌发率和萌发指数则先增大后减小,在40%光照强度下达到最大值.两树种幼苗存活率在全光照(100%光照)下均为0,在5%～60%光照处理下则随着光照强度的减弱而显著降低.两树种幼苗根长、地径和株高对光梯度变化的响应趋势一致,随着光照强度的减弱,根长显著减小,地径和株高则先增大后减小,在5%光照强度下达到最小.随着光照强度的减弱,杉木幼苗根、茎、叶及总生物量降低,木荷幼苗生物量积累在15%～60%光照强度下较高, 5%光照强度下最小,且相同光照强度下,木荷幼苗各部分生物量均大于杉木.两树种幼苗应对低光环境时,表现出较大的茎和叶的生物量分配比,而根生物量比和根冠比降低.表明杉木苗期生长不耐阴,需要相对较强的光照,而木荷苗期具有较强的耐阴性,对弱光环境的适应性更强,能够在郁闭的林冠下定植和正常生长.     

Plasticity in seedling morphology,biomass allocation and physiology among ten temperate tree species in response to shade is related to shade tolerance and not leaf habit

• Mechanisms of shade tolerance in tree seedlings, and thus growth in shade, may differ by leaf habit and vary with ontogeny following seed germination. To examine early responses of seedlings to shade in relation to morphological, physiological and biomass allocation traits, we compared seedlings of 10 temperate species, varying in their leaf habit (broadleaved versus needle‐leaved) and observed tolerance to shade, when growing in two contrasting light treatments – open (about 20% of full sunlight) and shade (about 5% of full sunlight).
• We analyzed biomass allocation and its response to shade using allometric relationships. We also measured leaf gas exchange rates and leaf N in the two light treatments.
• Compared to the open treatment, shading significantly increased traits typically associated with high relative growth rate (RGR) – leaf area ratio (LAR), specific leaf area (SLA), and allocation of biomass into leaves, and reduced seedling mass and allocation to roots, and net assimilation rate (NAR). Interestingly, RGR was not affected by light treatment, likely because of morphological and physiological adjustments in shaded plants that offset reductions of in situ net assimilation of carbon in shade. Leaf area‐based rates of light‐saturated leaf gas exchange differed among species groups, but not between light treatments, as leaf N concentration increased in concert with increased SLA in shade.
• We found little evidence to support the hypothesis of a increased plasticity of broadleaved species compared to needle‐leaved conifers in response to shade. However, an expectation of higher plasticity in shade‐intolerant species than in shade‐tolerant ones, and in leaf and plant morphology than in biomass allocation was supported across species of contrasting leaf habit.

     

光和不同打破种子休眠方法对紫茎泽兰种子萌发及幼苗状态的影响

紫茎泽兰是著名的外来入侵植物,作为入侵的第一步,发芽及其幼苗生长应该与其强入侵能力有关.基于此,通过不同光照强度处理和不同打破休眠方法的双因素实验,旨在探讨紫茎泽兰种子是否具有需光萌发特性以及低温、水杨酸、聚乙二醇,硝酸钾等常规打破休眠方法和光照如何共同影响其萌发、幼苗生长等问题.结果表明:在全光照条件下,不同处理的紫茎泽兰种子的萌发率均大于63％,铝箔纸覆盖的遮光条件(0.23％光照)萌发率均大于60％,而在完全黑暗条件下,其萌发率较低(均小于30％),这表明紫茎泽兰种子具有需光萌发的特性.有别于以往对其它植物种子的报道,低温处理、水杨酸处理、聚乙二醇处理和硝酸钾处理不能代替光照打破种子休眠,显示紫茎泽兰种子可能处于一种强迫休眠状态(种子静态).全光照与水杨酸处理、PEG处理对幼苗生长具有交互影响:黑暗下水杨酸处理浓度与幼苗生物量成正相关(P＜0.05),但全光照和加铝箔下不相关(P＞0.05);全光照下PEG处理浓度与根长显著正相关(P＜0.05),而加铝箔和黑暗下不相关(P＞0.05).紫茎泽兰种子需光萌发特征及其幼苗生长特点是人为破坏表土壤、深层土壤种子库地表化导致快速入侵的基础.结果也为通过引入适宜树种造林来控制光照因子对紫茎泽兰进行生态控制提供了理论依据.     

Mycorrhiza and seedling establishment in a subarctic meadow: Effects of fertilization and defoliation

Abstract. Question: How does changing resource availability induced by fertilization and defoliation affect seedling establishment and mycorrhizal symbiosis in a subarctic meadow? Location: 610 m a.s.l., Kilpisjärvi (69°03’N, 20°50’E), Finland. Methods: A short‐term full‐factorial experiment was established, with fertilization and defoliation of natural established vegetation as treatments. Seeds of two perennial herbs Solidago virgaurea and Gnaphalium norvegicum were sown in natural vegetation and their germination and growth followed. At the final harvest we measured the response in terms of arbuscular mycorrhizal (AM) colonization, biomass and nitrogen concentration of the seedlings and the established vegetation. Results: Germination rate was negatively affected by defoliation in the unfertilized plots. The shoot biomass of S. virgaurea seedlings was reduced by the defoliation and fertilization treatments, but not affected by their interaction. In G. norvegicum, the germination rate and the seedling shoot biomass were negatively correlated with moss biomass in the plots. In the established plants the arbuscular colonization rate was low and defoliation and fertilization treatments either increased or did not affect the colonization by AM fungi. In the seedlings, the colonization rate by AM fungi was high, but it was not affected by treatments. Both seedlings and established plants were colonized by dark septate fungi. Conclusions: Reduction of plant biomass by herbivores can have different effects on seedling growth in areas of high and low soil nutrient availability. The weak response of AM colonization to defoliation and fertilization suggests that AM symbiosis is not affected by altering plant resource availability under the conditions employed in this study.     

GERMINATION AND GROWTH OF BIRD-DISPERSED PLANTS: EFFECTS OF SEED SIZE AND LIGHT ON SEEDLING VIGOR AND BIOMASS ALLOCATION

I examined germination and seedling growth in nine species of fleshy-fruited plants from Washington and Idaho to assess their relative responses to sun and shade. I allowed seeds to germinate over a period of 500 days, and grew the seedlings in a greenhouse for 35 days prior to harvest. Cumulative percentage germination of six species approximated logistic curves. Species with larger seeds were more shade-tolerant, which resulted largely from greater biomass allocation to roots by these species. Seedlings of Rosa gymnocarpa, Sorbus scopulina, Symphoricarpos albus, Clintonia uniflora, and Streptopus amplexifolius grew larger in open sun than in shade (35% open sun), whereas those of Actaea rubra, Disporum trachycarpum, Smilacina racemosa, and Smilacina stellata showed no differences. Percentage root biomass was higher in sun than in shade for R. gymnocarpa, S. scopulina, S. albus, C. uniflora, and S. amplexifolius, but lower for S. stellata. In C. uniflora, S. racemosa, and S. stellata, seeds from unripe fruits failed to germinate. The results suggest that light gaps resulting from periodic disturbance of canopy influence recruitment of bird-dispersed species differentially and thereby contribute to maintaining high species richness and diversity in understories of temperate coniferous forests.     

Carbon uptake and respiration in above-ground parts of a Larix decidua × leptolepis tree

Summary Shade needles of hybrid larch (Larix decidua × leptolepis) had the same rates of photosynthesis as sun needles per dry weight and nitrogen, and a similar leaf conductance under conditions of light saturation at ambient CO₂ (A_max). However, on an area basis, A_max and specific leaf weight were lower in shade than in sun needles. Stomata of sun needles limited CO₂ uptake at light saturation by about 20%, but under natural conditions of light in the shade crown, shade needles operated in a range of saturating internal CO₂ without stomatal limitation of CO₂ uptake. In both needle types, stomata responded similarly to changes in light, but shade needles were more sensitive to changes in vapor pressure deficit than sun needles. Despite a high photosynthetic capacity, the ambient light conditions reduced the mean daily (in summer) and annual carbon gain of shade needles to less than 50% of that in sun needles. In sun needles, the transpiration per carbon gain was about 220 mol mol^–1 on an annual basis. The carbon budget of branches was determined from the photosynthetic rate, the needle biomass and respiration, the latter of which was (per growth and on a carbon basis) 1.6 mol mol^–1 year^–1 in branch and stem wood. In shade branches carbon gains exceeded carbon costs (growth + respiration) by only a factor of 1.6 compared with 3.5 in sun branches. The carbon balance of sun branches was 5 times higher per needle biomass of a branch or 9 times higher on a branch length basis than shade branches. The shade foliage (including the shaded near-stem sun foliage) only contributed approximately 23% to the total annual carbon gain of the tree.     

Effect of water stress on seed germination and seedling growth inOryza sativa L.

The effect of water stress induced by application of polyethylene glycol 6000 during seed germination and seedling growth ofOryza sativa L. cv. IAC 165 was analysed. The seed germination was inhibited by the decrease in the water potential of the medium, the inhibition being greater under white light than under continuous darkness. When the seedling was submitted to water stress (-0.51 MPa) white light inhibited growth of root, coleoptile-and leaf, while under no stress conditions white light caused increase in growth of root and leaf and only inhibition of coleoptile growth.     

Seed Size,Seed Germination,and Seedling Survival of Brazilian Tropical Tree Species Differing in Successional Status1

Seed germination and seedling establishment patterns have been used to classify species as shade tolerant or intolerant. The main objective of this research was to investigate, under controlled conditions, seed germination of species from different successional positions as well as to follow seed germination and seedling survival under natural shade in the field. The species studied were Solarium granuloso‐leprosum, Trema micrantha, Cecropia pachystachya, Croton piptocalyx, Bauhinia forficata subsp. pruinosa. Senna macranthera, Schizolobium parahyba, Piptadenia gonoacantha, Chorisia speciosa, Pseudobombax grandiflorum, Ficus guaranitica, Esenbeckia leiocarpa, Pachystroma longifolium, Myroxylon peruiferum, and Hymenaea courbaril. Field trials were carried out at Santa Genebra Municipal Reserve, Campinas, SP, Brazil, at the forest edge and in the understory. No significant correlations were detected between successional status and seed size or seed water content. Light‐regulated germination was present only in small‐seeded species. In field experiments, most species, including the light‐sensitive ones, were able to germinate under the canopy, where a low red/far‐red ratio predominates. Most species, mainly those of early‐ and intermediate successional positions, presented low seedling survival rates under shade. Myroxylon peruiferum was the most shade tolerant species, while 5. granuloso‐leprosum, C. speciosa, P. gonoacantha, F. guaranitica, T. micrantha, and 5. parahyba were the most shade intolerant. These latter species showed little or no survival under the shade conditions.     

Germination,growth and survival of <Emphasis Type="Italic">Berberis thunbergii</Emphasis> DC. (Berberidaceae) and <Emphasis Type="Italic">Berberis thunbergii</Emphasis> var. <Emphasis Type="Italic">atropurpurea</Emphasis> in five natural environments

Germination, growth and survival of green Berberis thunbergii and its purple ornamental form, Berberis thunbergii var. atropurpurea, were compared in five natural environments (full sun meadow, edge of woods, moist woods, dry woods, pine woods) to determine whether these two forms have a similar ability to naturalize. Berberis thunbergii and Berberis thunbergii var. atropurpurea had similar germination rates of about 25% at the end of 3 years. Most of the seed germination occurred in year one (89%), with a small amount of additional germination in year two (10%), and even less in year three (1%). Greatest germination occurred in the moist woods and full sun meadow sites and the least occurred at the pine woods site. Germination was reduced in the pine woods environment by the thick leaf litter layer present there. Barberry seedling survival during the first year was only 22% and survival dropped to 11.3% by the end of 2 years. Purple barberry seedlings had a lower 2 year survival rate than green barberry. There was no difference in seedling growth between purple and green barberry seedlings, but surviving seedling growth rates at the five environments were comparable. Seedlings achieved maximum growth in the edge of woods environment, but also grew well in the full sun meadow environment. At harvest, the full sun meadow had the greatest number of seedlings present, while no seedlings survived in the pine woods site.     

Morphological plasticity,photosynthesis and chlorophyll fluorescence of <Emphasis Type="Italic">Athyrium pachyphlebium</Emphasis> at different shade levels

Athyrium pachyphlebium C. is a popular ornamental fern with considerable shade tolerance. The aim of this study was to investigate how the mature sporophytes acclimate to different light levels and to obtain an optimal light environment for their growth both in natural forest canopy and in urban landscapes. Plant growth and morphology, photosynthetic light-response curves and chlorophyll (Chl) fluorescence were measured at four different light levels (45% full sunlight, 30%, 20% and 8%). As the light intensities declined from 45% to 20%, seedling height, crown growth, foliage number and plant lifespan increased significantly. Seedlings grown at 20% light level were vigorous with great ornamental value. Plants grown in deep shade (8% light) showed severe symptoms of lodging and in 45% full sun, the plants showed highlight-stress symptoms. Seedlings in high light levels exhibited a higher light-saturated photosynthetic rate (P _max), light compensation point (LCP), light saturation point (LSP) and a reduced ability for nonphotochemical quenching (NPQ) of excess light than those in low light levels. However, seedlings in low light exhibited greater efficiency in absorbing and utilizing light energy, characterized by higher chlorophyll b (Chl b) and electron transport rate (ETR). These results indicated that a light level of about 20% full sun appeared to be optimal for A. pachyphlebium when both physiological and morphological performance in the landscape were considered.     

Early growth and nutritional response to resource competition in cocoa-shade intercropped systems

Intercropping is often promoted for effective mutualism between species, thus compensating for external inputs. However, for optimal farm design resulting in superior production and nutrition, an accurate assessment of plant inter- and intra-specific competition is required. In predominant shade tree-cocoa (Theobroma cacao) systems, inconclusive evidence remains on species interactions, limitations to resource availability and subsequent growth and nutritional response, particularly in early growth. We examined cocoa biomass and foliar nutrition as well as nutrient supply through rates of decomposition and N mineralization after 1-year growth. Our approach employed fertilization and mixed planting treatments in an additive design of cocoa in monoculture (control), under artificial shade, and intercropped under two separate shade species (Terminalia superba and Newbouldia laevis). Intercropping had no effect on cocoa biomass production in comparison to monoculture cocoa. However, artificial shading stimulated foliage and root production both with and without fertilization, suggesting strong effects of light regulation on growth in the absence of belowground competition. Nutritionally, intercropping suppressed K uptake in cocoa foliage as K concentration was reduced by 20–25%, signifying dilution of this nutrient, presumably due to interspecific competition for mobile elements. Foliar N content under N. laevis was raised, where N concentration kept up with growth under this intercropped species. Intercropping also delayed decomposition rates, suggesting slower but sustained release of available nutrients into the topsoil. Cocoa under artificial shade, both with and without fertilization, exhibited the greatest nutrient responses as compared to unfertilized monoculture cocoa, where P uptake was stimulated most (175 and 112%), followed by K (69 and 71%), and then N (54 and 42%). Intercropping with shade trees failed to increase cocoa biomass, however, nutrient uptake was sustained for N and P, suggesting low interspecific competition. When fertilizers are undesirable or unavailable, intercropping of appropriately selected shade trees will not competitively suppress early growth of cocoa but will improve light regulation and nutritional status of cocoa saplings.     

Early seedling growth of pine (Pinus densiflora) and oaks (Quercus serrata,Q. mongolica,Q. variabilis) in response to light intensity and soil moisture

In climatic chambers seed germination and seedling growth of Pinus densiflora Sieb. et Zucc., Quercus serrata Thunb., Quercus mongolica Fisch. ex Turcz. and Quercus variablilis Bl. were investigated as functions of light intensity and soil moisture. In Korea these tree species occur widely and form mixed forests with different distributions. Species clearly differed in the pattern of germination and early seedling growth between light and soil treatments. The germination of pine did not differ between the experimental treatments until the breaking of the primary buds. After that, light intensity was the deciding factor for further development. In the most moist treatment (approx. field capacity) growth of the pine seedlings was strongly inhibited. For the three oak species, differences between experimental treatments first occurred after complete formation of primary leaves. Seed development strongly correlated with the weight of the acorn. The large seeded Q. variabilis (acorns with mean weight of 4.7 g) developed faster and reached larger dimensions towards the end of the experiment than Q. mongolica (2.8 g per acorn) and Q. serrata (0.9 g per acorn). Regarding height and biomass growth, the oak species showed a higher shade tolerance than pine. The proleptic shoot growth was clearly influenced by the light intensity. Root formation was favoured by a high exposure to light. In case of the oak species reduction of soil moisture increased the length of primary roots and the number of secondary roots.     

Different responses to shade of evergreen and deciduous oak seedlings and the effect of acorn size

An evergreen oak species, Cyclobalanopsis multinervis, and a deciduous oak species, Quercus aliena var. acuteserrata were grown from acorns under two light levels (full sunlight and shade at about 18 % of full sunlight, simulating the light intensities in forest clearings and gaps, respectively) for one growing season. Three hypotheses were tested: (i) the deciduous species grows faster than the evergreen species in forest gaps and clearings; (ii) the deciduous species responds more strongly in terms of growth and morphology to variation in light climate than the evergreen species; and (iii) seedling size is positively correlated to acorn size. The results showed: (i) at both light levels, the deciduous seedlings gained significantly more growth in biomass and height than the evergreen seedlings; (ii) both species produced significantly more biomass in full sunlight than in shade, without showing any significant difference in height between treatments. Increase in light intensity improved the growth of the deciduous seedlings more strongly; (iii) at a similar age, the deciduous seedlings showed a greater response in leaf morphology and biomass allocation to variation in light levels, but when compared at a similar size, biomass allocation patterns did not differ significantly between species; (iv) bigger acorns tended to produce larger seedlings, larger leaf sizes and more leaf area, between and within species. These differences demonstrate that the deciduous species is gap-dependent and has the advantage over the evergreen species in forest gaps and clearings.     

In vitro seed culture and seedling development of Calopogon tuberosus

A major obstacle to native orchid production is difficulty in seed germination. Culture media and light effects on seed germination of Calopogon tuberosus var. tuberosus, a native orchid with horticultural potential, were studied. Culture media included Knudson C, Malmgren modified terrestrial orchid, and PhytoTechnology orchid seed sowing. Effects of 8 weeks continual darkness, 8 weeks 16-h photoperiod, 2 weeks dark followed by 6 weeks 16-h photoperiod, 4 weeks dark followed by 4 weeks 16-h photoperiod, and 6 weeks dark followed by 2 weeks 16-h photoperiod were examined. Percent seed germination was highest on Knudson C after 8 weeks culture; however, seedling development was enhanced on PhytoTechnology seed sowing medium during 8 weeks culture under a 16-h photoperiod. This suggests that while KC and darkness promoted seed germination, P723 and light enhanced further seedling development. Seedlings of C. tuberosus readily acclimated to greenhouse conditions.     

遮荫对青桐幼苗生长性状与化学计量特征的影响

营养元素含量及化学计量比可反映植物器官营养元素的分配及互作关系,亦可反映其营养利用效率及生长环境的养分限制状况.以青桐(Firmiana platanifolia)幼苗为材料,分析4种不同光强(全光照,50％、75％和95％遮荫)对青桐幼苗生长,C、N、P、K含量及其化学计量特征的影响.结果 表明:遮荫对青桐幼苗的生长...