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1.
Relationships between relative growth rate (RGR), endogenous gibberellin (GA) concentration and the response to application of gibberellic acid (GA3) were studied for two inbred lines of Plantago major L., which differed in RGR. A4, the fast-growing inbred line, had a higher free GA concentration than the slow-growing W9, as analyzed by enzyme immunoassay. GA3 application increased total plant weight and RGR3 particularly for the slow-growing line. Chlorophyll a content and photosynthetic activity per unit leaf area were decreased, while transpiration rate was unaffected by GA3 application. The increase in RGR by GA3 application was associated with an increased leaf weight ratio; specific leaf area and percentage of dry matter in the leaves were only temporarily affected. Root respiration rate per unit dry weight was unaffected.
The correlation between low RGR, low GA concentration and high responsiveness to applied GA3 supports the contention that gibberellins are involved in the regulation of RGR. However, the transient influence of GA3 application on some growth components suggests the involvement of other regulatory factors in addition to GA.  相似文献   

2.
The role of gibberellin (GA) in leaf elongation has long been known, however, its involvement in whole shoot growth and biomass allocation is much less clear. We studied the effects of exogenously supplied GA3 and paclobutrazol, an inhibitor of GA biosynthesis, on these processes in Aegilops caudata and Aegilops tauschii , species with contrasting leaf growth characteristics. In both species, addition of GA3 increased leaf elongation rate (LER) through its promoting effect on both cell size and cell number, while paclobutrazol decreased it. Similarly, GA3 increased biomass allocation to the leaves, mainly leaf sheaths, at the cost of allocation to the roots, whereas paclobutrazol had the opposite effect in both species. Despite the increase in LER and biomass allocation to the shoot upon GA3 application, the relative growth rate (RGR) remained constant. Specific leaf area (SLA) was only temporarily affected by GA3 addition. Our results show that the inherent differences in LER and biomass allocation between the slow-elongating A. caudata and the fast-elongating A. tauschii are considerably reduced by the exogenous supply of GA3 to the slow-elongating species, or paclobutrazol to the fast-elongating one. This suggests a role for gibberellins in explaining inherent differences in leaf area expansion and biomass allocation between the two species in this study.  相似文献   

3.
The relative growth rate of pot-grown plants of Poa pratensis L. cv. Holt, origin 69s°N, was increased by 20–40% by photoperiod extension with low intensity incandescent light from 8 to 24 h at 9–21°C. The main increase occurred over the 14 to 18 h photoperiod range. The true photoperiodic nature of the response was demonstrated by the effectiveness of night interruption in stimulating growth. Fortnightly sprayings with gibberellic acid (GA3) (3 × 10-6 to 3 × 10-5 M ) mimicked all the effects of long days, whereas (2-chloroethyl)-trimethylammonium chloride (CCC) counteracted the effects of long days. Both growth substances exhibited pronounced interactions with photoperiod, GA3 being most effective in short days and CCC in long days. The growth stimulation, whether caused by long days or GA3, was exerted mainly through increases in individual and total leaf area. This was associated with a reduction in CO2, exchange rate and a parallel fall in specific leaf weight. Proportionally, however, the increase in leaf area was greater than the fall in CO2 exchange rate, resulting in a 38 to 118% increase in photosynthesis per leaf. No evidence was found of any direct and promotive effect of transition to long days on the CO2 exchange rate of already expanded leaves.  相似文献   

4.
Effects of gibberellins A1, A4/7, A9, A19 and A20 and growth retardants were studied on shoot elongation in seedlings of Salix pentandra L. The growth-retarding effects of CCC and ancymidol were antagonized by all the gibberellins tested. The novel plant growth regulator prohexadione (free acid of BX-112), which is suggested to block 3β-hydroxylation of gibberellins, effectively prevented shoot elongation in seedlings grown under long photoperiod. Initiation of new leaves was only slightly reduced. GA1, but not GA19 and GA20, was active in overcoming the inhibition of stem elongation of seedlings, treated with prohexadione, GA19, GA20 and GA1 are native in S. pentandra , and the results are compatible with the hypothesis that GA1 is active per se in shoot elongation, and that the effect of GA19 and GA20 is dependent on their conversion to GA1.
A mixture of GA4 and GA7 was as active as GA1 in promoting shoot elongation in seedlings treated with prohexadione, while GA9 showed slight activity only when applied at high doses.  相似文献   

5.
Plant species exhibit great differences in heavy metal accumulation and tolerance. In this study we compared interspecific differences in responses to Cadmium (Cd) stress among 10 C3 grass species by growing hydroponically under the conditions of different Cd treatments (0, 5, 10 and 50 μM). Responses of plant shoot dry mass to Cd treatments (resistance) were separated into avoidance (the response of shoot Cd concentration to Cd treatments) and tolerance (the response of shoot dry mass to shoot Cd concentration). The relative growth rate (RGR) and leaf structural properties of plants were measured under optimum growth condition. There were large differences in resistance, avoidance and tolerance among the species. Avoidance and tolerance were attributed independently to total Cd resistance. Resistance and tolerance were correlated negatively with RGR, leaf water content (LW), specific leaf area (SLA), leaf elongation rate (LER), and leaf length (LL), but the leaf dry matter concentration (LMDC), and nuclear DNA content showed a positive correlation with resistance and tolerance. These results indicate a trade-off between growth rate and tolerance to Cd stress. Species with higher Ca/Mg ratios showed low avoidance (r = −0.943***), suggesting uptake inhibition by Ca2+ to develop avoidance against Cd stress.  相似文献   

6.
Three rapid cycling Brassica rapa genotypes were grown in greenhouse conditions to investigate the possible relationships between endogenous gibberellin (GA) content and shoot growth. Endogenous GA1 GA3 and GA20 were extracted from stem samples harvested at 3 weekly intervals and analyzed by gas chromatography-mass spectrometry with selected ion monitoring, using [2H2]-GA1 and [2H2]-GA20 as quantitative internal standards. During the first 2 weeks, GA levels of the dwarf, rosette ( ros ), averaged 36% of levels in normal plants (on a per stem basis). Levels in the tall mutant, elongated internode (ein) , were consistently higher, averaging 305% of levels in normal plants.
Differences in shoot height across the genotypes resulted from varying internode length which resulted from epidermal cell length and number being increased in ein and decreased in ros relative to the normal genotype. The exogenous application of GA3 to normal plants increased cell length while the application of paclobutrazol (PP333), a triazole plant growth retardant, reduced cell size. Thus, exogenous GA manipulations mimicked the influence of the mutant genes ros and ein. The dwarf, ros , had reduced shoot dry weights and relative growth rates compared to the other genotypes. Total dry weights were similar in ein and the normal genotype but stem weights were increased in ein , compensating for decreased leaf weights. Thus, the gibberellin-deficiency of ros resulted in generally reduced shoot growth. The overproduction of endogenous GA by ein did not result in enhanced shoot growth but rather a specific enhancement of internode elongation and stem growth at the expense of leaf size.  相似文献   

7.
Potassium promotes growth in several plant tissues. Elongation growth of the hypocotyls of Amaranthus caudatus L. ev. Lalsag is mainly controlled by gibberellins, but K+ also promotes growth. In the present study the interaction of K+ with gibberellin (GA3) and chlorocholine chloride (CCC) has been investigated. When K+ was applied externally in the dark, hypocotyl growth was promoted in the seedlings. External application of GA3 did not promote growth in the dark. GA3 was effective in the light and K+ was synergistic with GA3 in promoting elongation. Application of CCC in the dark makes the seedlings sensitive to GA3. The inhibition of growth by CCC was also reversed by K+. The results indicate a possible role of K+ in GA3 induced elongation of hypocotyls.  相似文献   

8.
The effect of an elevated atmospheric CO2 concentration on growth, photosynthesis and root respiration of Plantago major L. ssp. major L. was investigated. Plants were grown in a nutrient solution in growth chambers at 350 and 700 μl I−1 CO2 during 7 weeks. The total dry weight of the Co2-enriched plants at the end of this period was 50% higher than that of control plants. However, the relative growth rate (RGR) was stimulated only during the first half of the growing period. The transient nature of the stimulation of the RGR was not likely to be due to end-product inhibition of photosynthesis. It is suggested that in P. major , a rosette plant, self-shading causes a decline in photosynthesis and results in an increase in the shoot: root ratio and a decrease in RGR. CO2-enriched plants grow faster and cosequently suffer more from self-shading. Corrected for this ontogenetic drift, high CO2 concentrations stimulated the RGR of P. major throughout the entire experiment.  相似文献   

9.
'York Imperial' apple seedlings ( Malus domestica Borkh.) were continuously supplied via the roots with paclobutrazol [(2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol)], a triazole GA biosynthesis inhibitor, at 0.68 μ M in a nutrient solution. In comparison to controls, seedlings treated with paclobutrazol for 66 days showed a 91% reduction in shoot length, a 66% reduction in leaf area but only a 17% reduction in leaf number. This effect could be reversed by GA3 applied to the foliage at 71.4 μ M 0, 19 or 35 days after paclobutrazol was initially supplied and leaf area values for paclobutrazol-treated seedlings given both treatments did not differ significantly from controls. Plots of growth data indicate linearity of shoot longitudinal growth of GA3-treated seedlings. Leaf area increase was non-linear after GA3 treatment up to approximately 30 days, when the rate dropped. On a per shoot basis, leaf weight closely followed leaf area but on a per unit area basis, paclobutrazol-treated leaves were heavier than controls; GA3 applications temporarily reversed this trend.  相似文献   

10.
Gibberellins and photoperiodic control of shoot elongation in Salix   总被引:1,自引:0,他引:1  
Effects of exogenous gibberellins GA53, GA44, GA19, GA20 and GA1 on photoperiodically controlled shoot elongation in seedlings of Salix pentandra L. were studied. Gibberellins GA20 and GA1 induced shoot elongation under short days (SD) and could substitute for a transfer to long day (LD), while gibberellins A53, A44 and A19 were inactive. In seedlings exposed to a prolonged SD-treatment (30 days) there was a significant positive interaction between a transfer to LD and a treatment with GA20 and GA1 on shoot elongation. In addition, GA19 enhanced the growth promotive effect of LD in these seedlings. The results are compatible with the suggestion that conversion of GA19 to GA20 is blocked under SD. This effect is supposed to be an early process leading to the cessation of shoot elongation under SD. Responsiveness of the seedlings to LD and to a GA-treatment gradually decreased with an increasing length of exposure to SD.  相似文献   

11.
Cessation of shoot elongation in seedlings of Salix pentandra L. is induced by short photoperiod. Gibbereliin A9 (GA9) applied either to the apical bud or injected into a mature leaf, induced shoot elongation under a short photoperiod of 12 h, and GA9 could completely substitute for a transfer to a long photoperiod. When [3H]GA9 or [2H2]GA9 was injected into a leaf, no [3H]GA9 was detected in the elongating apex and only traces of [3H]GA9 were found in the shoot above the treated leaf. By the use of gas chromatography-mass spectrometry (GC-MS), [2H2]GA20 was identified as the main metabolite of [2H2]GA9 in both the shoot and the treated leaf. In addition, [2H2]GA1 and [2H2]GA29 were also identified as metabolites of [2H2]GA9. These results are consistent with the hypothesis that exogenous GA, promotes shoot elongation in Salix through its metabolism to GA20 and GA,.  相似文献   

12.
Fifteen different gibberellins (GA's) were tested for their ability to induce elongation growth under short day conditions in seedlings of Salix pentandra L. GA's were applied either to the apex or they were injected into a mature leaf. GA3 was highly active and also GA4+7 and GA4 showed high activity. GA1, GA2, GA5, GA9, GA13, GA20, GA36 and GA47 showed moderate activity. GA16, GA17, GA27 and GA41 exhibited low or no activity in doses up to 10 μg per plant. In general, a better growth response was obtained with an application to the apex than with an injection into the leaf.  相似文献   

13.
Summary Bean and tomato plants were grown in solution culture root media containing pre-determined concentrations of gibberellin A3 (GA), 1-naphthaleneacetic acid (NAA), N6-benzyladenine (BA), (2-chloroethyl)trimethylammonium chloride (CCC), and at atmospheric levels of 300 and 1000 ppm of CO2. Net assimilation rates (NAR), relative growth rates (RGR), leaf area ratios (LAR), root to top dry weight ratios (R/T) and changes in dry weight, size, and form of each organ were recorded.Gibberellin had no effect on RGR of either plant species but increased the NAR of tomatoes at 1000 ppm CO2. Total dry weight was only slightly affected by GA but root growth and R/T were markedly depressed. CCC had no effect on NAR, but decreased RCR and LAR. Root growth of beans and R/T in both plants were promoted by CCC. NAR and RGR were strongly inhibited by BA and NAA. Inhibition of stem and leaf growth by CCC and NAA was greater than that for roots; thus, R/T ratios were increased. Root branching was promoted by NAA.High (1000 ppm), compared to the low (300 ppm), atmospheric levels of CO2 generally promoted root growth and produced an increase in the R/T, both in the absence and presence of chemical treatment. The multiplicity of effects of the rootabsorbed chemical growth substances and CO2 on growth and photosynthesis is discussed.Journal article No 3883 of the Michigan Agricultural Experiment Station.NATO Fellow, University of Pisa, Italy.  相似文献   

14.
Short photoperiod induces growth cessation in seedlings of Norway spruce ( Picea abies (L.] Karst.). Application of different gibberellins (GAS) to seedlings growing under a short photoperiod show that GA9 and GA20 can not induce growth. In contrast application of GA, and GA4 induced shoot elongation. The results indicate that 3β-hydroxylation of GA9 to GA4 and of GA20 to GA1 is under photoperiodic control. To confirm that conclusion, both qualitative and quantitative analyses of endogenous GAs were performed. GA1, GA3, GA4, GA7, GA9, GA12, GA15, GA15, GA20, GA29, GA34 and GA51 were identified by combined gas chromatography-mass spectrometry in shoots of Norway spruce seedlings. The effect of photoperiod on GA levels was determined by using deuterated and 14C-labelled GAs as intermal standards. In short days, the amounts of GA9, GA4 and GA1 are less than in plants grown in continuous light. There is no significant difference in the amounts of GA3, GA12, and GA20 between the different photoperiods. The lack of accumulation of GA9 and GA20 under short days is discussed.  相似文献   

15.
Aims Invasive species often have higher relative growth rates (RGR) than their native counterparts. Nutrient use efficiency, total leaf area and specific leaf area (SLA) are traits that may confer RGR differences between natives and invasives, but trait differences are less prominent when the invasive species belongs to the same plant functional type as the dominant native species. Here, we test if traits displayed soon after germination confer an early size advantage. Specifically, we predicted that invasive species seedlings grow faster than the natives because they lack trade-offs that more strongly constrain the growth of native species.Methods We quantified plant morphological and physiological traits and RGR during early seedling growth at high and low nutrient levels in three dominant perennial native C4 grasses: Panicum virgatum L. (switchgrass), Schizachyrium scoparium (Michx.) Nash (little bluestem) and Andropogon gerardii Vitman (big bluestem); and a perennial C4 exotic invasive grass, Sorghum halepense (L.) Pers. (Johnsongrass).Important findings After 2 weeks of growth, Johnsongrass seedlings had greater biomass, SLA and photosynthetic nitrogen use efficiency, but lower leaf N concentrations (% leaf N) and root:shoot ratio than natives. As growth continued, Johnsongrass more quickly produced larger and thicker leaves than the natives, which dampened the growth advantage past the first 2 to 3 weeks of growth. Investment in carbon gain appears to be the best explanation for the early growth advantage of Johnsongrass. In natives, growth was constrained by an apparent trade-off between allocation to root biomass, which reduced SLA, and production of leaves with high N content, which increased carbon gain. In Johnsongrass, root:shoot ratio did not interact with other traits, and % leaf N was decoupled from RGR as a result of a trade-off between the positive indirect association of % leaf N with RGR and the negative direct association of % leaf N with RGR.  相似文献   

16.
17.
林木对不同形态氮素具有选择性吸收特征,铵态氮和硝态氮是植物吸收的主要氮素形态.为了明确刨花楠对铵态氮和硝态氮的吸收差异,采用盆栽试验方法,以铵态氮和硝态氮为氮源,以1年生刨花楠实生苗为研究对象,以当地山地红壤为基质,设置了7种不同的铵硝比配施添加试验,研究氮素形态和配比对刨花楠幼苗生长和叶片性状的影响.结果 表明:不同...  相似文献   

18.
Anthocyanin synthesis in radish ( Raphanus sativus L. cv. Scarlet Globe) seedlings after treatment with chlorocholine chloride (CCC) and gibberellic acid (GA) has been investigated. CCC promotes and GA3 inhibits the synthesis. When both substances are given together, CCC reverses the inhibition caused by GA3. Simultaneous external feeding of anthocyanin precursors (sucrose and phenylalanine) reverses the GA3 inhibition. A higher amount of total free amino acids, in particular phenylalanine, was present in CCC-treated seedlings compared to controls grown on distilled water. The amount of phenylalanine was lower in seedlings treated with both CCC and GA3 as compared to seedlings treated with CCC alone, and total free sugars (reducing plus non-reducing) was lower in CCC treated seedlings than in controls grown on distilled water. We conclude that CCC and GA3 control the anthocyanin synthesis at the level of precursors.  相似文献   

19.
Understanding how growth and development of durum wheat cultivars respond to drought could provide a basis to develop crop improvement programmes in drought-affected tropical and subtropical countries. A greenhouse experiment was conducted to study the responses of five durum wheat cultivars to moisture stress at different developmental phases. Phenology, total dry matter (TDM), relative growth rate (RGR), leaf area ratio (LAR), net assimilation rate (NAR), leaf weight ratio (LWR), specific leaf area (SLA) and shoot:root ratio were compared. Pre-anthesis moisture stress delayed phenological development, whereas post-anthesis moisture stress accelerated it. TDM accumulation rate was different between drought-resistant and susceptible cultivars. RGR and its components changed with age and moisture availability. Drought-resistant cultivars had a high RGR in favourable periods of the growing season and a low RGR during moisture stress. In contrast, the drought-susceptible cultivar (Po) showed an opposite trend. LAR explained the differences in RGR (r=0.788) best, whereas the relationship between NAR and RGR was not significant. Even though both LWR and SLA were important factors determining the potential growth rate, LWR was of major importance to describe cultivar differences in LAR, and consequently in RGR. The drought-resistant cultivars Omrabi-5 and Boohai showed vigorous root development and/or a low shoot:root ratio. It is concluded that biomass allocation is the major factor explaining variation in RGR among the investigated durum wheat cultivars.  相似文献   

20.
den Hertog  J.  Stulen  I.  Lambers  H. 《Plant Ecology》1993,104(1):369-378
The response ofPlantago major ssp,pleiosperma plants, grown on nutrient solution in a climate chamber, to a doubling of the ambient atmospheric CO2 concentration was investigated. Total dry matter production was increased by 30% after 3 weeks of exposure, due to a transient stimulation of the relative growth rate (RGR) during the first 10 days. Thereafter RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the first two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration was stimulated throughout the experimental period. Dry matter allocation over leaves stems and roots was not affected by the CO2 level. SLA was reduced by 10%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of the experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric CO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for nearly 50% of the C budget at all stages of the experiment and in both treatments.Abbreviations LAR leaf area ratio - LWR leaf weight ratio - RGR relative growth rate - R/S root to shoot ratio - RWR root weight ratio - SLA specific leaf area - SWR stem weight ratio  相似文献   

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