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1.
Heidrun Huber Jan de Brouwer Hannie de Caluwe Jelmer Weijschedé Niels P. R. Anten 《Evolutionary ecology》2008,22(3):399-416
Increased cell number and cell length both contribute to shade induced elongation of petioles which enables stoloniferous
plants to place their leaf lamina higher up in the canopy. Although petiole elongation is assumed to be beneficial, it may
also imply costs in terms of decreased biomechanical stability. We test the hypothesis that shade induced elongation changes
the biomechanical properties of petioles and that the underlying mechanisms, cell division and cell elongation, differentially
affect biomechanical properties. This was done by subjecting 14 genotypes differing in the relative contribution of cell size
and cell number to shade induced elongation responses to high light conditions and to simulated canopy shade. Developmental
traits (cell size and cell number), morphological traits characterizing the petioles, as well as biomechanical characteristics
were measured. Our results show that, comparable to stems of non-clonal plants, the rigidity of a petiole’s tissue (the Young’s
modulus) increases, leading to increased flexural stiffness of petioles subjected to shading. Increased flexural stiffness
proved to be associated with increased performance under shaded conditions. Our results also indicate that cell number affected
the material properties and the flexural stiffness of petioles. However, the degree and pattern of the effects differed between
light environments. Shade induced increase in cell number translated into shade induced increase of Young’s modulus and flexural
stiffness. Genotypes producing relatively larger cells under shaded conditions experienced a decrease in tissue rigidity.
In concert our results indicate that the pattern of selection on flexural stiffness, and thereby also on shade induced changes
of cell number and cell size differs among light environments.
An erratum to this article can be found at 相似文献
2.
The effects of mechanical stress and spectral shading on the growth and allocation of ten genotypes of a stoloniferous plant 总被引:2,自引:0,他引:2
BACKGROUND AND AIMS: Because plants protect each other from wind, stand density affects both the light climate and the amount of mechanical stress experienced by plants. But the potential interactive effects of mechanical stress and canopy shading on plant growth have rarely been investigated and never in stoloniferous plants which, due to their creeping growth form, can be expected to respond differently to these factors than erect plants. METHODS: Plants of ten genotypes of the stoloniferous species Potentilla reptans were subjected to two levels of mechanical stress (0 or 40 daily flexures) and two levels of spectral shading (15 % of daylight with a red:far red ratio of 0.3 vs. 50 % daylight and a red:far red ratio of 1.2). KEY RESULTS: Mechanically stressed plants produced more leaves with shorter more flexible petioles, more roots, and more but less massive stolons. Responses to spectral shading were mostly in the opposite direction to thigmomorphogenesis, including the production of thinner, taller petioles made of more rigid tissue. The degree of thigmomorphogenesis was either independent of light climate or stimulated by spectral shading. At the genotypic level there were no clear correlations between responses to shade and mechanical stress. CONCLUSIONS: These results suggest that in stoloniferous plants mechanical stress results in clones with a more compact, shorter shoot structure and more roots. This response does not appear to be suppressed by canopy shading, which suggests that wind shielding (reduced mechanical stress) by neighbours in dense vegetation serves as a cue that induces shade avoidance responses such as increased petiole elongation. 相似文献
3.
Previous studies have shown that internodes and petioles of closely related erect and stoloniferous species show marked differences
in their response to shading. Vertical structures show strong elongation responses while horizontal structures show significantly
smaller elongation responses. This paper reports an experiment designed to test whether internodes and petioles on orthotropic
(vertically oriented) and plagiotropic (horizontally oriented) shoots produced by the same plant, also show such differential
responses. The study species, Glechoma hirsuta, produces plagiotropic shoots in its vegetative stage and orthotropic shoots during its generative stage. Shoots of G. hirsuta were grown either in full daylight or under simulated canopy shade. Internode and petiole elongation, biomass investment
patterns and other growth-related parameters were measured on plants in each light treatment. In orthotropic shoots the length
of internodes responded more strongly to shading than the length of petioles, while the opposite was true for plagiotropic
shoots, confirming the hypothesis that vertical spacers have higher degrees of shade-induced plasticity than horizontally
oriented spacers. Growth and development of horizontally oriented shoots was reduced by shading, whereas that of vertically
oriented shoots was unaffected by light treatment. The results are discussed in terms of the differences in function of vertically
and horizontally oriented spacers, and the probable benefits of plasticity in enhancing essential activities including photosynthesis,
habitat exploration and seed dispersal.
Received: 23 December 1996 / Accepted: 19 July 1997 相似文献
4.
Shade avoidance in the clonal herb Trifolium fragiferum/: a field study with experimentally manipulated vegetation height 总被引:1,自引:0,他引:1
In herbaceous canopies light availability can show high degrees of spatial variability in a vertical and also in a horizontal direction. Stoloniferous plants are hence likely to encounter differences in light availability during their ontogenetic development. Different mechanisms, such as petiole elongation, plasticity in internode length and branching, and an enhanced allocation to sexual reproduction have been suggested to represent viable shade-avoidance mechanisms for clonal plants.In a field experiment we tested the response of the stoloniferous herb Trifolium fragiferum L. to experimentally manipulated vegetation heights. Naturally occurring clonal fragments were exposed to four different vegetation heights ranging from 0 cm (high light availability created by clipping the surrounding natural vegetation at ground level) to 20 cm (natural shading in closed canopy). The growth and development of individual clones was followed for two months. At the end of the experiment above-ground plant parts were harvested. Growth-related and morphological parameters (e.g., petiole and internode length) as well as patterns of meristem utilization (i.e., flowering, branching) were recorded.Neither primary stolon growth and biomass accumulation nor branching and flowering were significantly affected by treatments. However, increased vegetation height resulted in a reduced number of secondary ramets and also had strong positive effects on petiole length, leading to marked changes in the architecture of plants growing in canopies of different heights. In addition, the average weight of individual ramets on the primary stolon was markedly higher in plants exposed to taller vegetation as compared to shorter vegetation.The results of this study suggest the occurrence of a trade-off between clonal expansion (i.e., secondary ramet production) and the average size of clonal offspring. If grown under higher vegetation plants invested more into the size of individual ramets, especially into elongating petioles, and less into the growth and development of lateral branches. Placing leaf laminae higher up in the canopy results in an enhanced light interception which has apparently buffered negative effects of increased vegetation height on whole-clone biomass. Plants grown under shorter vegetation invested more into lateral spread by producing more, but smaller ramets. 相似文献
5.
Mo-Zhu Wang Hong-Li Li Chun-Xiang Liu Bi-Cheng Dong Fei-Hai Yu 《Journal of Plant Ecology》2022,15(4):795
克隆植物蛇莓对光照强度和养分条件的适应性可塑性
表型可塑性可帮助植物缓冲环境压力并使其表型与当地环境相匹配,但目前仅少数性状的可塑性被广泛认为是适应性的。为充分理解可塑性的适应性意义,仍需进一步研究更多的植物功能性状及其环境因子。本研究将匍匐茎克隆植物蛇莓(Duchesnea indica)的21个基因型种植于不同的光照和养分条件下,并利用选择梯度分析检测了形态和生理可塑性对光照强度和养分有效性变化的适应性值。在遮荫条件下,蛇莓适合度(果实数、分株数和生物量)降低,节间缩短变细,成熟叶叶绿素含量降低,但叶柄长度、比叶面积、老叶叶绿素含量均增加。在低养分条件下,植株叶柄缩短,叶面积缩小变厚,叶绿素含量降低,但果实数量和根冠比增加。选择梯度分析表明,叶柄长度和老叶叶绿素含量对光照变化的可塑性是适应性的,老叶和成熟叶叶绿素含量对养分变化的可塑性也是适应性的。因此,不同性状的可塑性适应值取决于特定的生态背景。该研究的发现有助于理解克隆植物表型可塑性响应环境变化的适应性意义。 相似文献
6.
Using a new experimental set up, the way in which height growth of stoloniferous plants is adjusted to that of their neighbours, as well as differences between genotypes in their ability to keep up with neighbour height growth were tested. Five Potentilla reptans genotypes inherently differing in petiole length were subjected to three experimental light gradients, involving light intensity and red : far-red ratio. Each plant was placed in a vertically adjustable cylinder of green foil, and the treatments differed in the speed of cylinder height increase and final height. Total weight of plants decreased from the 'Slow' to the 'Fast' treatment, while petiole length increased. Leaves reaching the top of the cylinder stopped petiole elongation, resulting in similar final heights for all genotypes in the 'Slow' treatment. In the 'Fast' treatment only the fastest-growing genotype maintained its position in the top of the cylinder and genotypes differed strongly in final height within the cylinders. Plants adjust their height growth to that of the surrounding vegetation, leading to height convergence in short light gradients that slowly increase. These adjustments and genotypic differences in ability to keep up with fast-growing neighbours can influence the outcome of competition for light. 相似文献
7.
Igual José M. Valverde Angel Rivas Raúl Mateos Pedro F. Rodríguez-Barrueco C. Martínez-Molina Eustoquio Cervantes Emilio Velázquez Encarna 《Plant and Soil》2003,254(1):115-123
Submergence stimulates elongation of the leaves of Rumex palustris and under laboratory conditions the maximum final leaf length (of plants up to 7 weeks old) was obtained within a 9 day period. This elongation response, mainly determined by petiole elongation, depends on the availability of storage compounds and developmental stage of a leaf. A starch accumulating tap root and mature leaves and petioles were found to supply elongating leaves with substrates for polysaccharide synthesis in expanding cell walls. Changes in the composition of cell wall polysaccharides of elongated petioles suggest a substantial cell wall metabolism during cell extension. Reduced starch levels or removal of mature leaves caused a substantial limitation of submerged leaf growth. From the 5th leaf onward enough reserves were available to perform submerged leaf growth from early developmental stages. Very young petioles had a limited capacity to elongate. In slightly older petioles submergence resulted in the longest final leaf lengths and these values gradually decreased when submergence was started at more mature developmental stages. Submerged leaf growth is mainly a matter of petiole elongation in which cell elongation has a concurrent synthesis of xylem elements in the vascular tissue. Mature petioles still elongated (when submerged) by cell and tissue elongation only: the annular tracheary elements stretched enabling up to 70% petiole elongation. 相似文献
8.
Jelmer Weijschedé Rick Berentsen Hans de Kroon Heidrun Huber 《Evolutionary ecology》2008,22(3):383-397
We studied the effects of genotypic and plastic variation in vertical and horizontal spacer lengths on plant performance in
a stoloniferous herb subjected to opposing selection regimes. We hypothesized that longer vertical structures are beneficial
if plants are subjected to competition, but they should negatively affect plant performance if plants are exposed to aboveground
disturbance. To test these hypotheses we subjected 34 genotypes of Trifolium repens to competition and disturbance treatments. Competition was imposed by a grass canopy consisting of Lolium perenne, and disturbance was simulated by regularly clipping the target plants and all the surrounding vegetation at 1 cm above soil
level. Conform to our hypothesis, genotypes with longer vertical structures (petioles) produced fewer ramets than genotypes
with shorter petioles in the disturbance treatment. However, genotypes with longer petioles did not perform better under competition
than genotypes with shorter petioles. Genotypes with highly plastic vertical structures tended to produce more shoot mass
under competition, and they produced fewer ramets if subjected to disturbance. Unexpectedly, horizontal structures (stolon
internodes) expanded in response to competition which, furthermore, was associated with enhanced plant performance. However,
producing longer internodes is inherently associated with costs in terms of increased resource allocation to the longer structures,
but not to benefits in terms of increased resource capture. Positive correlations among the length and plasticity of vertical
and horizontal structures may explain the apparent positive effect of producing longer internodes on plant performance. Our
data thus support the notion that trait correlations may weaken selective forces acting on a focal trait in a specific environment
if opposing selection pressures act on genetically correlated traits. 相似文献
9.
光照强度和基质养分对匍匐茎草本金戴戴克隆生长和克隆形态的影响 总被引:3,自引:0,他引:3
在深度遮光 (光照强度为高光条件的 6 .2 5% ,约为自然光照的 5.3% )或低养分条件下 ,金戴戴 (HalerpestesruthenicaOvcz.)生物量、初级分株叶面积、分株总数、匍匐茎总数和总长度均显著减小 ,而比节间长和比叶柄长显著增加。在低养分条件下 ,金戴戴匍匐茎平均节间长显著增加 ,而匍匐茎分枝强度和分株数显著减小。这些结果与克隆植物觅食模型相符合 ,表明当生长于异质性生境中 ,金戴戴可能通过以克隆生长和克隆形态的可塑性实现的觅养行为来增加对养分资源的摄取。在深度遮光条件下 ,金戴戴平均间隔子长度 (即平均节间长和平均叶柄长 )均显著减小。这一结果与以往实验中匍匐茎草本间隔子对中度和轻度遮光 (光照强度为高光条件的 1 3%~ 75% ,>1 0 %的自然光照 )的反应不同。这表明 ,在深度遮光条件下匍匐茎克隆植物可能不发生通过间隔子可塑性实现的觅光行为。光照强度和基质养分条件的交互作用对许多性状如总生物量、匍匐茎总数和总长度、二级和三级分株数、分株总数、初级分株叶面积以及分枝强度均有十分显著的效应。在高光条件下 ,基质养分对这些性状有十分显著的影响 ;而在低光条件下 ,基质养分条件对这些性状不产生影响或影响较小。这表明 ,光照强度影响金戴戴对基质养分的可塑性反应。在深度遮光 相似文献
10.
Hélène Gautier Claude Varlet-Grancher Jeanne Marie Membré 《Physiologia plantarum》2001,112(2):293-300
Petiole response of white clover to variations in blue light (BL) was studied on the main axis and on primary and secondary branches. The objectives of the present work were to determine (1) the time course of petiole response to BL and (2) whether these responses were dependent on petiole location. Under BL, clover had shorter petioles, and the switch to conditions without BL increased the length of forthcoming petioles. The fitting of a logistic function was used to compare the effect of BL on final petiole length, maximum elongation rate and the duration of petiole elongation between axes and phytomers. Petiole response to BL was not dependent on its location within the plant (axis type or phytomer position along the axis). A reduction in BL induced a rapid increase in leaf elongation rate, despite a small decrease in the duration of petiole elongation. Moreover, petiole response was dependent on petiole stage of development: the increase in the maximum rate of petiole elongation was inversely proportional to the petiole stage of development at the time of the switch. We conclude that the effects of BL on petiole elongation were not dependent on its position within the plant, whereas internode elongation resulted from the integration of light environment at the plant level. The difference between the responses of orthotropic and plagiotropic organs of clover to BL is discussed in relation to their structural function and localisation in the canopy. 相似文献
11.
在深度遮光(光照强度为高光条件的6.25%,约为自然光照的5.3%)或低养分条件下,金戴戴(Halerpestes ruthenica Ovcz.)生物量、初级分株叶面积、分株总数、匍匐茎总数和总长度均显著减小,而比节间长和比叶柄长显著增加.在低养分条件下,金戴戴匍匐茎平均节间长显著增加,而匍匐茎分枝强度和分株数显著减小.这些结果与克隆植物觅食模型相符合,表明当生长于异质性生境中,金戴戴可能通过以克隆生长和克隆形态的可塑性实现的觅养行为来增加对养分资源的摄取.在深度遮光条件下,金戴戴平均间隔子长度(即平均节间长和平均叶柄长)均显著减小.这一结果与以往实验中匍匐茎草本间隔子对中度和轻度遮光(光照强度为高光条件的13%~75%,>10%的自然光照)的反应不同.这表明,在深度遮光条件下匍匐茎克隆植物可能不发生通过间隔子可塑性实现的觅光行为.光照强度和基质养分条件的交互作用对许多性状如总生物量、匍匐茎总数和总长度、二级和三级分株数、分株总数、初级分株叶面积以及分枝强度均有十分显著的效应.在高光条件下,基质养分对这些性状有十分显著的影响;而在低光条件下,基质养分条件对这些性状不产生影响或影响较小.这表明,光照强度影响金戴戴对基质养分的可塑性反应.在深度遮光或低养分条件下,金戴戴可能通过减小匍匐茎节间粗度(增加比节间长)来增加或维持其相对长度,从而更有机会逃离资源丰度低的斑块. 相似文献
12.
We tested whether the degree of shade-induced plasticity in petiole length and leaf area is related to the mean trait value expressed under high-light conditions, and to what extent trait values expressed under high-light and shaded conditions affect plant performance. Thirty-four Trifolium repens genotypes were used with a wide range of petiole lengths and leaf areas. Plants were subjected to a high-light environment and two shading regimes: homogeneous shading and a vertical light gradient. Absolute petiole elongation in response to both shading treatments and absolute leaf area expansion in response to homogeneous shading were independent of the trait values expressed in high light. Consequently, relative plasticity was higher for genotypes with lower high-light trait values. Plasticity was associated with enhanced plant performance in a vertical light gradient but not in homogeneously shaded conditions. We also found costs associated with the ability to express plasticity. Our results suggest that selection can act separately on trait values expressed under high-light conditions and on the degree of plasticity. 相似文献
13.
研究了匍匐茎型克隆草本金戴戴(Halerpestes ruthenica) 4种基株(基因型)对不同盐分处理(0,85.5, 171.0, 256.5和342.0 mM NaCl)的表型可塑性。随着盐分浓度的增加,实验植物与生长相关的性状指标 (如植株干重、总叶面积、分株数和总匍匐茎长度) 显著减小。植株干重、总叶面积和总匍匐茎长度具有显著的基株间差异。实验植物与形态相关的性状指标 (如平均叶柄长和根冠比) 对盐分梯度具有可塑性并具有显著的基株间差异;而其它形态指标 (如平均节间长、比节间长和比叶柄长) 相似文献
14.
Effects of nitrogen on mesophyll cell division and epidermal cell elongation in tall fescue leaf blades 总被引:18,自引:5,他引:13
Leaf elongation rate (LER) in grasses is dependent on epidermal cell supply (number) and on rate and duration of epidermal cell elongation. Nitrogen (N) fertilization increases LER. Longitudinal sections from two genotypes of tall fescue (Festuca arundinacea Schreb.), which differ by 50% in LER, were used to quantify the effects of N on the components of epidermal cell elongation and on mesophyll cell division. Rate and duration of epidermal cell elongation were determined by using a relationship between cell length and displacement velocity derived from the continuity equation. Rate of epidermal cell elongation was exponential. Relative rates of epidermal cell elongation increased by 9% with high N, even though high N increased LER by 89%. Duration of cell elongation was approximately 20 h longer in the high- than in the low-LER genotype regardless of N treatment. The percentage of mesophyll cells in division was greater in the high- than in the low-LER genotype. This increased with high N in both genotypes, indicating that LER increased with cell supply. Division of mesophyll cells adjacent to abaxial epidermal cells continued after epidermal cell division stopped, until epidermal cells had elongated to a mean length of 40 micrometers in the high-LER and a mean length of 50 micrometers in the low-LER genotype. The cell cycle length for mesophyll cells was calculated to be 12 to 13 hours. Nitrogen increased mesophyll cell number more than epidermal cell number: in both genotypes, the final number of mesophyll cells adjacent to each abaxial epidermal cell was 10 with low N and 14 with high N. A spatial model is used to describe three cell development processes relevant to leaf growth. It illustrates the overlap of mesophyll cell division and epidermal cell elongation, and the transition from epidermal cell elongation to secondary cell wall deposition. 相似文献
15.
Shade-avoidance syndrome is characterized by the formation of elongated petioles and unexpanded leaf blades under low-intensity light, but the genetic basis for these responses is unknown. In this study, two-dimensional mutational analysis revealed that the gene for phytochrome B, PHYB, had opposing effects in the leaf petioles and leaf blades of Arabidopsis, while the ROT3, ACL2, and GAI genes influenced the length of leaf petioles more significantly than the length of leaf blades. Anatomical analysis revealed that the PHYB and ACL2 genes control the length of leaf petioles exclusively via control of the length of individual cells, while the GAI, GA1 and ROT3 genes appeared to control both the elongation and proliferation of petiole cells, in particular, under strong light. By contrast, both the size and the number of cells were affected by the mutations examined in leaf blades. The differential control of leaf petiole length and leaf blade expansion is discussed. 相似文献
16.
Effects of leaf blade narrowness and petiole length on the light capture efficiency of a shoot 总被引:11,自引:0,他引:11
Akio Takenaka 《Ecological Research》1994,9(2):109-114
Effects of the length: width ratio of a leaf blade and petiole length on shoot light capture were studied with computer simulation.
Both a larger length: width ratio and longer petiole contributed to larger light capture per unit leaf area due to a reduced
aggregation of leaf area around the stem. Other conditions being equal, shoots with narrow leaves and no petioles and those
with wide leaves with petioles showed similar light capture as long as the mean distance of the leaf blade from the stem was
the same. In shoots with a short internode and/or distichous phyllotaxis, however, narrow leaves contributed more to avoiding
mutual shading than wide leaves with petioles. The predominance of light coming from a higher angular altitude also favored
narrow leaves. The possible consequences of these results in the adaptive geometry of plant architecture are discussed. 相似文献
17.
Phenotypic plasticity allows plants to cope with environmental heterogeneity. Environmental variation among populations may select for differentiation in plasticity. To test this idea, we used the annual plant Geranium carolinianum, which inhabits old fields that are densely vegetated and lack canopy cover and wood margins with tree shade but less neighbor shade. Individuals from three populations of each habitat were planted in natural low and high light environments, and morphological traits important for light acquisition were measured. Old-field plants were more plastic, with greater elongation of petioles and internodes in low light than those from wood margins. This larger shade avoidance response suggests evolution of greater plasticity to neighbor shade than to the tree canopy. Fitness of old-field plants was high across both light environments, whereas fitness of wood-margin plants was reduced in low light. Selection favored longer internodes in low than high light. Finally, plasticity for internode length was negatively associated with fitness in high light, suggesting a cost of plasticity for this trait. Together these results indicate that shade-avoidance plasticity of petiole and internode length is adaptive. However, greater elongation of internode length may be constrained by the cost of plasticity expressed in high light. The evolution of plasticity appears to reflect a balance between its adaptive nature and its cost to fitness. 相似文献
18.
Z. Jovanovic T. Djakovic R. Stikic Lj. Prokic V. Hadzi-Taskovic Sukalovic 《Plant and Soil》2004,265(1-2):211-223
Two maize genotypes differing in leaf elongation rate (high-LER and low-LER) were used for the investigation of the effects of nitrogen deficiency on leaf growth and development and activity of enzyme cell wall peroxidase in the leaf growth zone. Plants were grown in a growth cabinet in perlite as a substrate and watered with complete N-NO3 solution (+N) and N-NO3 deficient solution (–N). Comparison between the investigated genotypes showed that final leaf length in both N treatments was related with LER, but not with the duration of leaf elongation. Faster leaf elongation rate in high-LER compared with low-LER genotype, was associated with longer growth zone, a bigger number of cells in it, and higher cell flux rate, although cell elongation rate was similar in both genotypes. These lines of evidence indirectly indicated that leaves of the faster growing genotype were characterized by higher meristematic activity. Nitrogen deficiency reduced the flux of cells and cell elongation rate, length of cell division zone and the number of cells in whole zone, significantly for both genotypes, although duration of cell elongation was increased and final epidermal cell length was unchanged. These results showed that N deficiency reduced both cell division and cell elongation, which in turn resulted in decreased leaf length and prolonged time for leaf development. Nitrogen deficiency significantly increased both bulk and segmental cell wall peroxidase activity in the growth zone of both investigated genotypes, thus showing an interaction between leaf growth cessation and enzyme activity. 相似文献
19.
N.K. Damayanthi Ranwala Dennis R. Decoteau Anil P. Ranwala William B. Miller 《Plant Growth Regulation》2002,38(2):157-163
Changes in soluble carbohydrate composition and concentration in leavesand petioles of watermelon (Citrullus lanatus (Thunb)Matsum and Nakai cv. Sugar Baby) seedlings during early stages ofphytochrome-regulated petiole elongation were investigated. Watermelon seedlingswere grown in a controlled environment with 350 molm–2 s–1 photosynthetically activeradiation (PAR) during a 12-h photoperiod. Low intensity end-of-day(EOD) light treatments (for 15 min) of red (R), far-red (FR) and FRfollowed by R (FR/R) were initiated when the seedlings were 14 days old.Seedling growth, and soluble carbohydrate concentration and composition inleaves and petioles were determined after 3 and 6 days of EOD light treatments.The EOD FR increased the petiole length and dry mass partitioned to petioles asearly as 3 days into the treatment. This increased petiole dry mass inFR-treated plants was accompanied with an increase in reducing sugar (glucoseand fructose) concentration in the petioles. Although both leaves and petiolesshowed this effect, the relative increase was greater in petioles than leaves.While the most abundant sugars in petioles were fructose and glucose, thepredominant sugars in leaves were sucrose, raffinose, and stachyose. Thephotoreversion of FR induced changes in growth and sugar concentrations by Rindicates the involvement of phytochrome in these processes. 相似文献
20.
Light with decreased red:far-red (R:FR) ratios may signal neighbor presence and trigger plant developmental responses. There is some evidence that plant canopies forage towards increased R:FR ratios, but it is unclear to what extent R:FR versus the total amount of photosynthetically active radiation (PAR) influences canopy foraging responses among forest trees. The objective of this study was to examine the relative importance of PAR and R:FR as photosensory cues leading to tree canopy foraging responses. Seedlings of Betula papyrifera Marshall (paper birch) were grown in an experimental garden. Each seedling was germinated and grown in its own shading structure and exposed to two spatially separated light environments, in a factorial design of PAR and R:FR. Plant canopy foraging was evaluated at the end of one growing season in terms of canopy displacement, canopy area, leaf number, direction of stem lean, petiole aspect, and lamina aspect with respect to experimental light treatments. Leaf number and canopy area were greater on the high PAR sides of plants, irrespective of the R:FR treatment. Seedling canopies were displaced towards the direction of high PAR, but this relationship was not significant across all treatments. Petiole aspect was random and showed no significant directedness towards any of the light treatments. Lamina aspect and the direction of stem lean were distributed towards the direction of high PAR, irrespective of the R:FR treatment. Overall, first-year B. papyrifera seedlings used PAR, rather than R:FR ratio, as a photosensory cue for canopy light foraging. 相似文献