Vegetative Shoot Growth Research Articles

Correlation of Endogenous Gibberellic Acid with Initiation of Mango Shoot Growth

Stems of mango (Mangifera indica L.) rest in a non-growing, dormant state for much of the year. Ephemeral flushes of vegetative or reproductive shoot growth are periodically evoked in apical or lateral buds of these resting stems. The initiation of shoot growth is postulated to be primarily regulated by a critical ratio of root-produced cytokinins, which accumulate in buds and by leaf-produced auxin, which decreases in synthesis and transport over time. Exogenously applied gibberellic acid (GA 3 ) delays initiation of bud break but does not determine whether the resulting flush of growth is vegetative or reproductive. We tested the hypothesis that endogenous GA 3 , which influences release of these resting buds, may decrease in stem tips or leaves with increasing age of mango stems. GA 3 and several other GAs in stem tip buds and leaves were identified and quantified in stems of different ages. The major endogenous GAs found in apical buds and leaves of vegetative mango stems were early 13-hydroxylation pathway gibberellins: GA 1 , epi-GA 1 , GA 3 , GA 19 , GA 20 , and GA 29 , as identified by gas chromatography-mass spectrometry (GC-MS). A novel but unidentified GA-like compound was also present. The most abundant GAs in apical stem buds were GA 3 and GA 19 . Contrary to the hypothesis, the concentration of GA 3 increased within buds with increasing age of the stems. The concentrations of other GAs in buds were variable. The concentration of GA 3 did not change significantly with age in leaves, whereas that of most of the other GAs declined. GA 1 levels were greatest in leaves of elongating shoots. These results are consistent with the concept that rapid shoot growth is associated with synthesis of GAs leading to GA 1 . The role of GA 3 in delaying bud break in mango is not known, but it is proposed that it may enhance or maintain the synthesis or activity of endogenous auxin. It, thereby, maintains a high auxin/cytokinin ratio similar to responses to GA 3 that maintain apical dominance in other plant species.

Usefulness of Apogee® for the PA Apple Industry

Excessive tree vigor is a significant production problem for the PA apple industry. A series of experiments were conducted from 1994 to 1999, which indicated that Apogee® could effectively reduce vegetative shoot growth. Results from 1994 to 1996 have previously been reported (HortScience 31:598, 32:558). In 1997, 16 treatments composed of four rates (0, 63, 125, and 250 ppm) and four timings (22 May; 4, 11, and 24 June) in various combinations, were applied as dilute handgun sprays. These treatments were applied to sixth leaf `York Imperial' apple trees. Ten peripheral shoots, at a height of 2 m, were tagged and measured on 21 May, 9 and 30 June, 16 July, 12 Aug., and on 10 Oct. Shoots treated with 63, 125, or 250 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June were from 65% to 76% of the length of the controls (25.5 cm). Treated shoots were from 69% to 78% of the length of the controls following sprays with 63 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June. Shoots treated with 125 ppm on 22 May followed by 0 or 63 ppm on 4, 11, or 24 June were from 69% to 73% of the length of the controls. The later applications (11 and 24 June) of 250 ppm gave no growth control but the 22 May treatment gave a 30% reduction in growth. In 1999, dilute handgun sprays of 125, 125, 83, and 83 ppm were made on 22 May and on 4, 11, and 24 June, respectively. Cultivars treated were `Spartan', `Delicious', `York Imperial', `Gala', and `Mutsu'. The length of 10 peripheral shoots at 2 and 3 m were measured on 28 July and on 12 Aug. All cultivars responded and on 12 Aug. treated terminal shoot lengths ranged from 33% to 55% of the controls. With reduced vegetative tree vigor many horticultural factors will be improved. In addition, the severity of shoot fire blight can be reduced and the control of all pests that prosper on young succulent leaves will be easier, especially apple aphids and obliquebanded leafrollers. Major factors to be considered in developing an efficacious Apogee® program appear to be initial tree vigor, length of growing season, and crop load. An initial application at 1 to 3 inches of terminal growth is probably the most critical factor.

Suppression of Fireblight in Apple Shoots by Prohexadione-calcium following Experimental and Natural Inoculation

Suppression of Fireblight in Apple Shoots by Prohexadione-calcium following Experimental and Natural Inoculation

Reproductive-vegetative shoot growth interactions and relationship to non-structural carbohydrates in immature ponkan mandarin (Citrus reticulata Blanco)

SummaryThe relationship of leaf carbohydrates to vegetative and reproductive growth during an annual growth cycle in young trees of ponkan (Citrus reticulata Blanco) was monitored over two consecutive seasons. Fruiting, return bloom and fruit set was greater and more uniform in high fruit-load trees. These trees developed less vegetative growth and produced fruit with higher total soluble solids and skin colour than in trees with lower fruit loads. At anthesis, high fruit-set trees (20%) had higher starch and/or sucrose content in the leaves. Conversely, low fruit-load trees set less fruit (8%) despite having heavy return bloom and showed greater variation in fruit numbers per tree. They developed more vegetative shoot growth and had lower sucrose and/or starch content in the leaves at anthesis despite bearing fewer fruits per tree. Fruiting efficiency (fruits per cubic meter of canopy) was highest in the high fruit-load trees and lowest in the low-load and defruited trees.

Responses of vegetative and reproductive traits to elevated CO2 and nitrogen in Raphanus varieties

The relationships between the responses to elevated CO2 of the vegetative and reproductive phase were investigated in radish, used as a test system. The hypothesis that an increase in nonfoliar vegetative storage capacity promotes reproductive output was tested. Three cultivars of Raphanus sativus and the wild, Raphanus raphanistrum, differing in root to shoot ratios, were grown under two levels of CO2 and two levels of nitrogen fertilization. Varieties possessed different strategies of carbon storage and showed distinct responses to CO2 at each vegetative harvest time. Vegetative sinks of hypocotyls, petioles, and young blades were enhanced by CO2. Nitrogen promoted vegetative shoot growth, but did not enhance the reproductive response to CO2. By the end of the reproductive phase, varieties did not differ in total biomass. Reproductive response to CO2 may have been limited by the lack of an effect on the timing of flowering. Correlations in CO2 enhancement ratios were examined in 12 traits of each phase. Only vegetative total leaf area correlated with reproductive mass. Foliar starch correlated with decreased abortion. Enhancements in vegetative biomass did not correlate with any reproductive response. Detailed studies of the reproductive phase are needed to understand the whole-plant response to elevated CO2. Key words: elevated CO2, plant reproduction, nitrogen, starch, carbon allocation, source–sink.

Growth Responses and Allocation of Assimilates of Rice Seedlings by Paclobutrazol and Gibberellin Treatment

Paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)methyl-4,4-dimethyl-2-(1h-1,2,4-trizol-1-yl)penten-3-ol] effectively decreased vegetative growth of rice (Oryza sativa L.) seedlings and increased the chlorophyll content. The number of veins in a leaf, the calculated number of stomata per leaf, and the length of guard cells were not altered by the paclobutrazol treatment, suggesting an effect on cell elongation. The allocation pattern of carbohydrates was changed by either gibberellin (GA) or paclobutrazol treatment. GA3 induced more shoot growth and less accumulation of starch than the control and paclobutrazol-treated seedlings. Photosynthetic ability was not affected by either paclobutrazol or GA3 treatment. Paclobutrazol-treated plants allocated a smaller amount of photosynthates for vegetative shoot growth and stored more as starch in the crowns than the control and GA3-treated plants. The same starch degrading activity in the crown tissue of paclobutrazol-treated seedlings as in control plants suggests that the accumulated starch is utilized in a normal activity for growth including leaf emergence, tiller formation, and root production, resulting in improved seedling quality.

Off-season Production of Primocane-fruiting Red Raspberry Using Summer Pruning and Polyethylene Tunnels

The spring shoots of `Autumn Bliss' red raspberry (Rubus idaeus L. var. idaeus; primocane-fruiting type) were cut on 2, 16, 31 July and 15 and 30 Aug. with the objective of delaying fruit harvest into the off-season under mild winter climatic conditions. Cutting shoots in August delayed fruit harvest until February and April of the following year, but shoot growth was weak and fruit yield low (4.8 and 2.1 g/cane). July cuttings delayed harvest until October to January with acceptable fruit yield (63.5, 52.8, and 26.5 g/cane for 2, 16, and 31 July, respectively). The differences in cane height and total node and fruiting node count between the three cutting dates of July were small, but there was a constant decrease in leaf area per cane from the first to the third date and a sharp decrease in fruit yield from the second to the third date. Vegetative shoot growth was less affected than yield when summer cutting was delayed until the end of July to induce a later harvest. Fruit quality always reached acceptable standards. This study confirms the practicability of using summer-cutting of primocane-fruiting red raspberries to induce off-season fruit production under protected cultivation in mild winter climates.

Mycorrhizae, biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.

The Relationship between Growth and Development of Vegetative Shoots in Genotypes of Tall Fescue (Festuca arundinacea Schreb.)

In perennial grasses, shoot growth consists of: (a) the increase in the number of tillers (tillering), and (b) the increase in the size of tillers; while shoot development can be represented by an allometric relationship between these two components. This study examined how genetic differences in the developmental process of a shoot influence the various components of vegetative growth in 16 genotypes of a perennial grass, Festuca arundinacea Schreb. A negative correlation between the relative tillering rate (Rtil) and relative growth rate of single tillers (RGRtil) showed that the genotypes can be classified into two categories: genotypes producing few large tillers, and those producing many small tillers. The relative growth rate of the whole shoot (RGRshoot) correlated positively with RGRtil (r = 0·69**), but not with Rtil (r = 0·24). Root d. wt and the accumulation rate of nonstructural carbohydrate correlated negatively with Rtil and positively with RGRtil in spite of the absence of any apparent correlations with RGRshoot. These results demonstrate that: (1) the shoot developmental process has marked effects on various components of vegetative growth, and (2) the production of few large tillers results in higher carbon availability within a plant than the production of many small tillers.

Gibberellins and bud break, vegetative shoot growth and flowering in Metrosideros collina cv. Tahiti

Applications of the growth promotive gibberellins (GAs) GA4 and 2,2-dimethyl GA4, and of C-16,17 endo-dihydro GA5, which is known to promote flowering while inhibiting stem growth in the long-day grass Lolium temulentum, were made to micropropagated plants of Metrosideros collina cv. Tahiti, a highly ornamental cultivar with an intermittent flowering pattern. Gibberellin A4 and 2,2-dimethyl GA4 stimulated vegetative growth both in elongating shoots, and internodes of shoots developing from buds that were quiescent at the time of GA application. Abscission of the apices of expanding shoots, a feature of mature Metrosideros plants, was inhibited by these GAs, the rejuvenation of micropropagated plantlets being enhanced. However, C-16,17 endo-dihydro GA5 differed from GA4 and 2,2-dimethyl GA4 by having no promotive effects on vegetative growth, and no inhibition of apical abscission. Notwithstanding this contrasting effect on vegetative growth, high doses of GA4 or C-16,17 endo-dihydro GA5 similarly reduced flowering on shoots to which either GA was applied. Reduced flowering in response to applied GAs is common in many woody angiosperms, and in this instance was probably the combined result of abortion of developing floral structures in quiescent buds, and a preferential inhibition of bud break for floral buds relative to vegetative buds, particularly by GA4. Finally, both C-16,17 endo-dihydro GA5 and GA4 strongly inhibited bud break in this woody angiosperm, although GA4 could initially stimulate bud break when applied to vegetative buds close to the expansion stage. The above findings, in toto, highlight the sensitivity of Metrosideros to both classes of GA in a variety of growth and development processes.

Dry matter partitioning in a tomato plant: one common assimilate pool?

The influence of the distance (transport resistance) between source and sink on dry matter distribution between fruits and vegetative parts in tomato was studied. In two glasshouse experiments, a control treatment (single-shoot plants, no truss removal) was conducted, together with two double-shoot treatments: double-shoot plants with no trusses removed from one shoot and all trusses removed at anthesis from the other shoot (100–0) and double-shoot plants with every second truss removed from both shoots (50–50). Plant growth and dry matter distribution was recorded by periodical destructive harvests, during a period of about 100 d after anthesis of the first truss. In experiment 2, plants were probably sink-limited. At the end of both experiments, 58–60% of dry matter was in the fruits for control plants, whereas for both double-shoot treatments this was 43% (Experiment 1) or 38% (Experiment 2). Until 60–65 d after first flowering, vegetative growth of the individual shoots in both double-shoot treatments was the same. Results supported the assumption of one common assimilate pool and showed no significant influence of distance (transport resistance) between source and sink on dry matter partitioning.

Yield and Seed Oil Content Response of Dwarf, Rapid-cycling Brassica to Nitrogen Treatments, Planting Density, and Carbon Dioxide Enrichment

Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.

Gender‐Specific Physiology, Carbon Isotope Discrimination, and Habitat Distribution in Boxelder, Acer Negundo

In the semiarid Intermountain West, boxelder, Acer negundo, var. interior, a deciduous, dieocious tree, exhibits significant habitat—specific sex ratio biases. Although the overall sex ratio (male/female) does not deviate significantly from one, the sex ratio is significantly male biased (1.62) in drought—prone habitats, while it is significantly female biased (0.65) in moist, streamside habitats. The causes underlying gender—specific habitat associations in this species are not known. We hypothesized that spatial segregation of the sexes is maintained by differences in gender—specific photosynthetic behavior, water relations characteristics, and both instantaneous and integrated water—use efficiency. Gender—specific physiological characteristics were measured and related to growth, reproduction, population age structure, and habitat distribution of male and female trees. Under both field and controlled—environment conditions, males and females differed significantly in a number of physiological traits. Males maintained lower stomatal conductance to water vapor (g), transpiration (E), net carbon assimilation (A), leaf internal CO2 concentration (ci), carbon isotope discrimination (△ an index of time—integrated ci and water—use efficiency), and higher instantaneous (A/E) and long—term (△) water—use efficiency than females. Furthermore, male trees exhibited greater stomatal sensitivity to both declining soil water content and increasing leaf—to—air vapor pressure gradients, a measure of evaporative demand. Higher rates of carbon fixation in female trees were correlated with higher g, higher leaf nitrogen concentrations, and greater stomatal densities. For females growing in both wet and dry habitats, vegetative shoots had higher growth rates than reproductive shoots, while for males, growth rates of the two shoot types did not differ. In streamside habitats, female trees exhibited significantly greater vegetative shoot growth when compared to male trees. In contrast, males showed slightly greater vegetative and much greater reproductive shoot growth in non—streamside habitats. Regardless of habitat or growing conditions, females allocated proportionately more of their aboveground biomass to reproduction than did males. These results suggest that (1) gender—specific physiological traits can help explain the maintenance of habitat—specific sex ratio biases in A. negundo along a soil moisture gradient, and (2) that the combination of the gender—specific physiology, growth, and allocation differences contribute to differences in the size (=age) structure of male and female plants within the population. Gender—specific physiological differences may have evolved as a product of selection to meet significantly different costs associated with reproduction in male and female plants.

柳井湾における春期から夏期のアマモＺｏｓｔｅｒａ ｍａｒｉｎａの生長様式

The growth of eelgrass Zostera marina in tidal flats was investigated in Yanai Bay, Seto Inland Sea, Japan, from late April to late July 1982. Field surveys were conducted seven times with a marking method at about 15 day intervals. In May and June, the fastest growth of vegetative shoots of eelgrass was observed. The average number of leaves on a vegetative shoot was 4.5 and the plastochrone interval was about 10 days. The average life of a leaf on a vegetative shoot was about 40 days. The growth rates of leaves 10 and 30 days after formation, were 2.5 cm/day and 0.5 cm/day, respectively. The growth rate of rhizomes was about 2cm/day in May. The formation of nodes was synchronized with a loss of leaves by washing away. In generative shoots, neither growth of rhizome nor branching was observed in the period of investigation. Spadices were fromed from late April and became dominant in June. In July, all spadices were washed away and subsequently all generative shoots withered. Our observation suggests that seeds were released together with the spadix when it was washed away, but not scattered one by one.

Effects of NaCl salinity on miniature dwarf tomato ‘Micro‐Tom’: I. Growth analyses and nutrient composition1

Abstract The growth and nutrient composition of miniature dwarf tomato selection Lycopersicon esculentum ’Micro‐Tom’ plants grown from seedling to harvest in solution batch culture at four different NaCl salinity levels (2.4 [control, no NaCl], 7.6, 12.8, or 18 dS‐m‐1 solution conductivities) was studied. Specific leaf area and relative growth rate generally decreased with increased NaCl. Shoot‐root, root mass, and leaf area ratios initially increased but later resumed control values. Although reduction in leaf area in response to higher NaCl was noted at 4 weeks, leaf and root dry mass was not significantly reduced until 12 weeks. At 12 weeks, enhanced carbohydrate partitioning toward shoot vegetative growth was observed in the highest NaCl level as reduced harvest index and increased leaf and stem mass ratios. An immediate proportional increase in leaf Na and decrease in Ca occurred with solution NaCl concentration. Although leaf K declined significantly between 4 and 8 weeks, there were no differences ...

Rates of corolla growth in tobacco determined with the plastochron index

The growth of vegetative and reproductive shoots of Nicotiana tabacum L. cv. Xanthi is analyzed with the plastochron index to estimate the relationship between corolla growth and time. The plastochron of leaves 9 through 20 declines steadily at each successive node. The flower plastochron increases steadily during the growth of an individual cyme, with the most distal flower to open having the longest plastochron. Variation in the flower plastochron is the result of variation in the rate of flower initiation, not the growth rate of individual flowers. The corolla has an extended phase of approximately constant relative growth in length (between 0.2 · d(-1) and 0.3 · d(-1)) until a peak of growth (0.5 · d(-1)) 2-3 d before anthesis. Corollas also have periodic peaks and troughs of growth that are low in amplitude (0.1 · d(-1)), but persist throughout most of corolla development. The pattern of corolla expansion contrasts strongly with earlier reports of the pattern of tobacco leaf growth.

USE OF CRYOPROTECTANTS FOR FROST PROTECTION IN PEACHES

Late spring freezes often result in significant flower bud kill in deciduous fruit trees. Some products have been marketed as frost protectant compounds which purportedly protect flower stigmas and ovaries from freezing injury and death. Two of these compounds, Frost Free and Frostgard, were tested at two locations in South Carolina over three years. Varieties `Junegold', `Loring', `Redhaven', and `Jefferson' were treated with Frost Free (FF) in years 1988-1990 and with Frostgard (FG) in 1990. Significant differences in fruit yield and vegetative growth occurred during this period, but no consistent trends were evident. In 1989, FF-treated `Redhaven' and `Jefferson' trees averaged 10.5 and 21.8 kg more fruit/tree than the controls. However, no lethal cold temperatures occurred during the bloom period. In 1990, FG-treated `Redhaven' trees averaged 8.0 kg more fruit/tree than the control trees. The fruit from FF-treated trees were lower in Brix, had less red color, and vegetative shoot growth was slightly greater than that of the FG and check trees. These data suggest that Frost Free may have plant growth regulator properties.

Effect of applied growth regulators and cultural treatments on flowering and shoot growth of Pinustabulaeformis

Fourteen treatments expected to promote and regulate flowering were administered to 7-year-old seedlings of Chinese pine (Pinustabulaeformis Carr.), and three were administered to 11-year-old grafted propagules. The cultural treatments, including root pruning, stem girdling, polyethylene mulching, and injection of gibberellin A3 (GA3) significantly increased male cone bud production of the young seedlings. For female flowering, however, only GA4 injection, alone and in combination with root pruning, had a statistically significant positive effect. N6-benzyladenine (BA) injection significantly decreased both male and female cone-bud production. There was no synergistic effect between the cultural and the hormonal treatments on flowering of the seedlings. Treatments with naphthaleneacetic acid dramatically enhanced male cone bud production of the grafted propagules, but did so at the expense of female cone bud production. The hormonal treatments (GA3, GA4, and BA injection) all promoted vegetative shoot growth of the treated seedlings. The cultural treatments generally inhibited shoot length growth and had no significant effect on diameter growth.

Gibberellic acid causes earlier flowering and synchronizes fruit ripening of coffee

The effect of 100 mgl−1 gibberellic acid (GA3) on flowering and fruit ripening synchrony, fruit set, fruit fresh weight, and vegetative growth were studied for different size classes of coffee (Coffea arabica L. cv. Guatemalan) flower buds. Flower buds that were > 4 mm, but not developed to the candle stage at the time of GA3 treatment, reached anthesis 20 days earlier than the controls, and their development was independent of precipitation, unlike the controls. Fruit from buds that were treated with GA3 at the candle stage showed earlier and more synchronous ripening than the control, although no differences in flowering were found during anthesis. Buds that were smaller than 4 mm at the time of treatment did not respond to GA3 applications. Treatment with GA3 did not affect fruit set, fresh weight of fruits, or vegetative shoot growth.

Seasonal control over allocation to reproduction in a tussock-forming and a rhizomatous species of Eriophorum in central Alaska.

The evergreen tussock-forming Eriophorum vaginatum revealed consistently earlier (c. 1 moth) phenology and greater biomass per tiller than the summergreen rhizomatous E. scheuchzeri in all four components measured (vegetative and reproductive shoots and stems) under the same climatic regime in central Alaska over one growing season. Greatest allocation to vegetative shoot growth occurred in mid-summer in both species. The tussock growth form of E. vaginatum raised shoot meristems 25-30 cm above the soil surface, where temperatures were warmer, permitting shoot growth to begin earlier in spring and continue longer in autumn than in E. scheuchzeri. Consequently, E. vaginatum was able to allocate reserves to reproductive tillers primarily in autumn and early spring, times when minimal reserves were required for vegetative growth. By contrast, the rhizomatous E. scheuchzeri had a more constrained growing season, and allocation to reproduction coincided with allocation to vegetative growth. For this reason, reserves were drawn down more fully in mid-summer in E. scheuchzeri than in E. vaginatum. The more conservative use of nutrient stores in E. vaginatum may relate to its great longevity, reduced allocation to reproduction (including low seedling recruitment), and relatively stable habitats. The mid-seasonal pulse of allocation to reproduction in E. scheuchzeri appears viable only in relatively fertile disturbed sites, where the soil nutrient supply is sufficient to support simultaneous allocation to vegetative growth and reproduction.