Tiller dynamics and assimilate partitioning in Lolium perenne with particular reference to flowering

The fate of 100 seedling plants of Lolium perenne L. was studied over a period of 2 years in a field plot. The birth and death of tillers and the production of inflorescences was followed, and the components of seed yield were recorded in detail in the first year. The pattern of distribution of ¹⁴CO₂ assimilated by the main shoot was examined at monthly intervals and during the first flowering season the distribution of ¹⁴C-assimilate from individual leaves and from the inflorescence was also studied. The capacity of individual tillers to assimilate ¹⁴CO₂ prior to flowering and the re-distribution of previously accumulated assimilate during seed growth were also assessed. Plants died at a more or less constant rate with time and only 54 survived to the end of the 2–yr period. First year mortality was associated with severe grazing or cutting but in the second year the death of ungrazed plants was observed. There was great variability in the production of tillers by surviving plants. In both years the number of live tillers per plant increased from July to the end of April with particularly rapid tillering in March and April establishing the maximum value for each year. There was a similar phase of rapid tillering after flowering in July. The number of live tillers per plant declined by 50% during stem elongation and inflorescence emergence and the majority of dead tillers were young secondary (in the first year) and tertiary (in the second year) tillers with a mean age of 40 days. Such tillers had poor assimilatory capacity prior to the onset of death and were not supplied with assimilate from the main shoot. Most of the plants surviving at the end of the experiment flowered in both years and one quarter of the maximum number of live tillers per plant recorded in April of each year produced inflorescences. The earlier a tiller was produced the greater was its chance of flowering and the greater its production of seed. The greater weight of seed produced was associated with the development of more seed-bearing florets per spikelet. There was relatively little export of “C-assimilate from the flowering main shoot, and the lower internodes formed the major sink for post-anthesis assimilate. The growth of seeds appeared to be relatively independent of the leaves for current assimilate. There was some evidence that assimilate accumulated in lower internodes was remobilised and utilised in the growth of seeds and new tillers. Overall, the results confirm the view that the grass plant is a dynamic population of short-lived tillers and indicate that increasing competition for assimilate at flowering exerts a major influence on the production and survival of tillers.     

Variations in Tiller Dynamics and Morphology in Lolium multiflorum Lam.Vegetative and Reproductive Plants as affected by Differences in Red/Far-Red Irradiation

Lolium multiflorum Lam, plants were grown in a growth room undertwo light sources with red/far-red ratios of 1·62 and0·84 but similar photosynthetically active radiation.In both situations the capacity to produce new tillers and thelight available per tiller decreased with canopy growth. Tilleringwas further reduced by the low red/far-red ratio while lightinterception and plant dry weight were unaffected by this treatment.In both reproductive and vegetative plants under the lower red/far-redratio the time between leaf expansion and the appearance ofa tiller in its axil was increased and the proportion of ‘maturebuds’ that developed was reduced. Irradiation with lowred/far-red advanced the reproductive development and increasedthe number of fertile tillers per plant. It also caused longerleaf sheaths, blades and reproductive shoots. The results suggestthat as canopy density increases the lower light interceptionper tiller and the photomorphogenic effect of low red/far-redratios may reduce the capacity to produce new tillers. Lolium multiflorum, Lam., annual ryegrass, tillering, tiller growth, leaf growth, flowering, light quality.     

Effect of the Duration of the Vegetative Phase on Shoot Growth, Development and Yield in Pearl Millet (Pennisetum americanum (L.) Leeke)

Craufurd, P. Q. and Bidinger, F. R. 1988. Effect of the durationof the vegetative phase on shoot growth, development and yieldin pearl millet (Pennisetum americanum (L.) Leeke).–J.exp. Bot. 38: 124–139 The duration of the vegetative phase (DVP) in millet, whichis the major cause of variation in the crop duration, has markedeffects on the number of productive tillers per plant and onmainshoot (MS) and tiller grain yield. Daylength extensionswere used to vary the DVP and the effect on factors affectingpanicle (tiller) number per plant and panicle yield examinedin millet hybrid 841A x J104, grown in the field at Hyderabad,India. Tiller appearance, shoot leaf appearance and leaf area,and stem and panicle growth, in both MS and primary tillers(PTs), were monitored at frequent intervals over the season.At maturity grain yield per shoot was measured The concept of thermal time was used to describe shoot development.The rates of tiller appearance and shoot leaf appearance werelinearly related to thermal time and were not affected by DVPtreatments. The duration of the growth phase from panicle initiationto flowering (GS2) and from flowering to maturity (GS3) was320 and 390 degree days (°Cd), respectively. There was nodifference in rates of leaf or tiller appearance or developmentbetween MS and PTs. Tiller appearance, tiller leaf appearanceand tiller apical development all ceased at the same time inthe later initiated PTs, approximately 550 °Cd from sowing,shortly after rapid stem growth had begun. Tillers that didnot survive were all vegetative or in the early stages of reproductivedevelopment at this time The rate of accumulation of dry matter per plant was similarin all DVP treatments, but in the longer DVP treatments a greaterproportion of the dry matter was partitioned to the MS. Mainshootstem and panicle growth rates were increased by a longer DVP,as was grain yield on the MS, and these were related to increasedMS leaf area. Concurrently, growth rates and yields in laterinitiated tillers were reduced in relation to their leaf areas.Stem growth rate was proportionately increased more than paniclegrowth rate in the longer DVP treatments and this, combinedwith a longer duration of stem growth, resulted in greater stemdry matter at maturity and, therefore, in reduced harvest index.     

EFFECTS OF SINGLE AND MULTIPLE EXPOSURES OF FERULIC ACID ON THE VEGETATIVE AND REPRODUCTIVE GROWTH OF PHASEOLUS VULGARIS BBL-290

Phaseolus vulgaris BBL-290 plants were grown in growth chambers in the Southeastern Plant Environment Laboratory and exposed to either single (at seedling, flower, or podfill) or multiple (biweekly or weekly) treatments of ferulic acid (FA). In the first experiment, plants were harvested one week after FA treatment (0, 1.0, 2.0 mM) and at final harvest (56 days old). FA delayed leaf expansion during the seedling and flowering stages. The total plant leaf area and the plant dry weight of plants treated with 1.0 and 2.0 mM FA as seedlings were reduced one week after treatment by 38–48%. The total plant leaf area and the plant dry weight of plants treated at flowering with 2.0 mM FA were reduced by 25% one week after treatment. Treatment with 2.0 mM FA at podfill caused the senescence and abscission of older leaves and reduced total plant leaf area, plant dry weight and mean pod dry weight by 54, 40, and 48%, respectively, one week after treatment. The plants treated at the seedling and flowering stages recovered by final harvest. In a subsequent experiment, FA (0, 0.50, 1.0, 1.5 mM) reduced total plant leaf area at the seedling and flowering stages but not at podfill. The youngest expanding leaves were most sensitive to FA at flowering. The leaf area of these leaves was reduced by 35 and 25%, one and two weeks after treatment, respectively. Their absolute growth rates were reduced from 31 to 56% one week after treatment at flowering. Their relative growth rates were reduced by 50% one week after treatment. Growth rates then recovered within two weeks after treatment. In the final experiment, biweekly exposures of FA (0.25, 0.50, 0.75, 1.0) reduced total plant leaf area but did not affect any other growth parameters. Weekly exposures of FA (0.25, 0.50, 0.75, 1.0) reduced total plant leaf area up to 34%, absolute growth rate up to 58%, leaf number up to 31% and pod number up to 58%. As the frequency of exposure to FA increased, the concentration necessary to affect bean plant growth and development decreased.     

GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE)

Individual tillers of timothy ( Phleum pratense ) growing from seed in pots were labelled and their life history studied over a period of two years.
The leaf axil position of the first-produced tiller depended on its time of origin. A minimum of five leaves on the parent axis was necessary before its appearance, and no tiller emerged from the axil of any of the three terminal leaves of a shoot.
Ear-bearing capacity was high in early-formed tillers, but decreased progressively with later dates of origin despite favourable day length; all tillers arising after the end of July failed to produce inflorescences. A greater proportion of tillers on the main stem formed ears than secondary tillers of the same age. Time of ear emergence varied only within a few days for all tillers arising before the end of April. The number of leaves formed up to ear emergence varied linearly with date of origin and tiller position, the lowest recorded number being six.
Dry weight and length of inflorescence as well as seed yield per tiller varied linearly with the date of origin of tillers. Primary tillers generally had longer and heavier inflorescences and produced more seed per stem than secondary tillers of the same age.
Tillers arising at all times were found to have a limited span of life, not normally exceeding just over a year. The mean age of ear-bearing tillers varied linearly with their date of origin. Death-rates of all tillers generally increased with their age. Relative death-rates of fertile and vegetative tillers rose rapidly in the autumn but decreased during winter and early spring. Vegetative tillers which elongated in the year of formation survived for a shorter time than equivalent tillers in which stem elongation was delayed until the following year.
The perennial habit of grasses is discussed in relation to tiller survival. Successive new formation and death of tillers keep the plant in a condition of continuous dynamic change.     

Tillers Do Not Influence Phytotoxicity of Imazamethabenz in Wild Oat (Avena fatua)

The response of wild oat to imazamethabenz varies with the growth stage, but the role of tillers in this regard is unclear. Removal of tillers at the three-leaf stage before spraying with imazamethabenz did not significantly affect the total shoot fresh weight measured 3 weeks later. The leaf area and dry weight of intact plants at the three-leaf stage were 17–21% greater than for plants with coleoptilar and first leaf main shoot tillers (T0 and T1) removed. The greater leaf area may have increased herbicide interception per plant. Similar fresh weight reductions in main shoot, total tillers, and total shoots were found whether imazamethabenz was applied to the plant at the two-leaf without tillers or the three-leaf with two tillers stage. Imazamethabenz applied only to the main shoot reduced total shoot dry weight more than an equivalent amount of imazamethabenz applied only to tiller T1 or applied over the whole shoot. Imazamethabenz had the least inhibitory effect on whole plant growth when applied only to T1. When ¹⁴C-herbicide was applied to the first main shoot leaf of plants at the three-leaf stage with two tillers, the ¹⁴C translocated 38% to roots, 33% to the main shoot, and nearly 30% to all tillers. When ¹⁴C-herbicide was applied to the first leaf of T1 then the ¹⁴C translocated 50% to T1, 25% to the main shoot, 20% to roots, and 5% to all other tillers. The translocation pattern and fresh weight values suggested that the presence of early tillers during herbicide application neither increased nor decreased imazamethabenz efficacy in wild oat. Received June 4, 1997; accepted June 5, 1997     

Canopy development of a determinate and an indeterminate cultivar of Vicia faba L. under contrasting plant distributions and densities

Field experiments were conducted in 1987 and 1988 to quantify differences in canopy formation between an indeterminate and a determinate genotype of Vicia faba L., grown at two plant densities and three spatial distributions. The number of stems per unit area produced by determinate plants was related to the growth rate before flowering. Leaf production per stem per unit of thermal time was similar in both plant types, but twice as many leaves per stem were produced by the indeterminate cultivar. The indeterminate cultivar produced fewer and smaller leaves in the warmer and drier weather of 1988 than in 1987. The determinate genotype produced similar sizes and numbers of leaves in both years, but fewer tillers developed in 1988 than in 1987. Accordingly, leaf mass per unit ground area was greater in 1987 than in 1988 in both genotypes. Except during early flowering, relationships between leaf mass and leaf area were constant, with higher specific leaf areas in the determinate than the indeterminate genotype. Shoot dry matter partitioning into leaves was identical in both years for indeterminate plants, but differed in determinate ones.
It is concluded that canopy development is regulated through individual leaf weight and leaf number per stem in non-tillering indeterminate, and by stem numbers per unit area in tillering determinate plants.     

The Effect of Soil Water Regimes on Leaf Water Potential, Growth and Development of Soybeans

The growth and development of soybeans (Glycine max L. cv. Amsoy) was studied at soil matric potentials of ?0.1 to ?1.0 bars. Chlorophyll, photosynthesis, and leaf nitrogen per plant was greatest at ?4 bars leaf water potential. Leaf area, number of internodes, plant height and dry weight of vegetative parts declined as leaf water potential decreased from ?2 to ?19 bars. Nitrogen content and nitrate reductase activity per g fresh weight determined the percentage protein of individual seeds but nitrogen content and nitrate reductase activity per plant determined the amount of total seed protein. The protein synthesized in the seed changed little in amino acid composition with changes in leaf water potential. Leaf water potentials above or below ?4 bars decreased yield, total protein and total lipid but plants produced the largest percentage of individual seed protein at ?19 bars leaf water potential.     

Interaction between the endophytic fungus Epichloe bromicola and the grass bromus erectus: effects of endophyte infection, fungal concentration and environment on grass growth and flowering

Epichloe bromicola is an endophytic fungal species that systemically and perennially colonizes intercellular spaces of leaf blades, leaf sheaths and culms of Bromus grass species. E. bromicola causes choke disease in B. erectus, suppressing maturation of most, if not all, host inflorescences. In an investigation of the interaction between fungus and host, we used a quantitative polymerase chain reaction technique to estimate the amount of fungal DNA, and thereby fungal concentration, in host plants. Fungal concentration was directly correlated with vegetative vigour of the plant, as measured by longest leaf length, number of tillers and vegetative above-ground biomass, suggesting that, during vegetative growth, the endophytic fungus is most beneficial for the plant when present in high concentrations. In contrast, the reproduction of the plant, as measured by the number of functional inflorescences, was inversely correlated with fungal concentration: the majority of infected plants, and all that were associated with high concentrations of fungi, were diseased. Thus, the benefit of endophyte infection for the plant is coupled with the disadvantages of infertility. Fungal concentration was shown to be at least in part genetically determined because fungal concentration differed significantly in different plant-endophyte genotype combinations (symbiotum). In a field experiment with normal and CO2-enriched environments, elevated CO2 levels favoured fungal reproductive vigour over host reproductive vigour, suggesting that these plant endophytes would be at a selective advantage in a corresponding environmental-change scenario. We conclude that a dynamic and complex relationship between fungal endophyte infection, fungal concentration, genotype and environment affects growth and fecundity of B. erectus and should contribute to the evolution of these plant-fungal interactions.     

Leaf and Tiller Production of Prairie Grass (Bromus willdenowii Kunth) and Two Ryegrass (Lolium) Species

A detailed morphological study of three prairie grass cultivars(Bromus willdenowii Kunth) was conducted under ‘vegetative’and ‘reproductive’ growth conditions (short andlong photoperiods) and at different temperatures. Perennialryegrass (Lolium perenne L.) and Westerwolds ryegrass (Loliummuhiflorum Lam.) were compared during vegetative growth. Prairie grass had higher leaf appearance rates (leaves per tillerper day) and lower site filling (tillers per tiller per leafappearance interval) than the ryegrass species. Tillering rates(tillers per tiller per day) were also lower, except under vegetativeconditions at 4C. Low tiller number in prairie grass was notdue to lack of tiller sites but a result of poor filling ofthese sites. Lower site filling occurred because of increaseddelays in appearance of the youngest axillary tiller and lackof axillary tillers emerging from basal tiller buds. In prairiegrass, no tillers came from coleoptile buds while only occasionallydid prophyll buds develop tillers. Low tiller number in prairiegrass was compensated for by greater tiller weight. Prairiegrass had more live leaves per tiller, greater area per leafand a high leaf area per plant. Considerable variation between cultivars was found in prairiegrass. The cultivar ‘Bellegarde’ had high leaf appearance,large leaves and rapid reproductive development, but had lowlevels of site filling, tillering rate, final tiller numberand herbage quality during reproductive growth. ‘Primabel’tended to have the opposite levels for these parameters, while‘Grasslands Matua’ was intermediate and possiblyprovided the best balance of all plant parameters. prairie grass, Bromus willdenowii Kunth, perennial ryegrass, Lolium perenne L., Westerwolds ryegrass, Lolium multiflorum Lam., temperature, photoperiod, leaf appearance, leaf area, tillering, site filling, tillering sites, yield     

Flowering Phenology and Gender Variation in Pennisetum typhoides

Because of the modular structure of pearl millet (an annual grass crop, Poaceae), different tillers of a plant share the same genotype but are subjected to different environmental conditions during their maturation. This allows investigation of the effects of tiller flowering phenology on allocation to resource-producing photosynthetic biomass, sexual functions, and thus tiller gender. All tillers of plants of two families collected from individual maternal plants (represented by 33 and 31 plants each) were analyzed. In both families, allocation to aboveground vegetative biomass decreased as flowering was delayed. On average, late-flowering tillers were 65% smaller than the first ones to flower. The proportion of biomass allocated to reproduction significantly increased with the flowering rank of the tillers, suggesting that translocations of assimilates occurred between early- and late-flowering tillers. In both families, late-flowering tillers produced significantly fewer pollen grains per stamen than early-flowering ones, and female reproductive allocation (expressed as seed mass per tiller) was also affected by flowering phenology. Tillers became increasingly female as flowering phenology progressed. This gender variation is possibly adaptive because pollination efficiency is maximized by plant height. Natural selection may favor a shift toward femaleness to maximize reproductive fitness in small, late-developing tillers.     

Light effects on development of an indeterminate plant

The peanut (Arachis hypogaea L.) plant is indeterminate in growth habit and day-neutral with respect to flower initiation. The Spanish-type cultivar used in this study begins flowering 3 to 4 weeks from planting under optimum environmental conditions. In this study, irradiance and photoperiod were used to alter the development of the peanut plant. Plants grown at low irradiance (300 microeinsteins per square meter per second) had the same number of leaves as the plants grown at high irradiance (500 microeinsteins per square meter per second), but they had a larger leaf surface area and were taller than plants grown at the high irradiance. However, flowering and other reproductive components (pegs, pods, and seeds) were reduced at low irradiance. Comparison of 8-, 12-, and 16-hour photoperiods at the high irradiance showed that the 16-hour photoperiod produced the largest amount of vegetative, but least amount of reproductive components. The plants grown at 8-hour photoperiod had one-third as much total leaflet area as plants grown at 16 hours, but six times more weight of mature seeds. The larger amount of photosynthetic surface (leaf area) did not result in more reproductive growth. The results indicate that the peanut plant may readily redistribute its available assimilates between vegetative and reproductive growth in response to irradiance and photoperiod.     

Effects of below- and above-ground herbivores on plant growth,flower visitation and seed set

Separate and combined effects of root and leaf herbivores on plant growth, flower visitation and seed set were tested in a factorial experiment using potted mustard, Sinapis arvensis, at an old fallow field. A 50% leaf removal by cabbageworms (Pieris rapae) when the seedlings had their first four leaves reduced plant height and shoot mass, and delayed the onset of flowering. Root herbivory by two wireworms (Agriotes sp.) over the whole experiment changed flower visitation; the number of flower visitors per plant was higher in plants with root herbivores than in plants without root herbivores. Combined leaf and root herbivory affected flowering period, number of fruits per plant and number of seeds per fruit. Plants attacked by leaf and root herbivores had a shorter flowering period and produced fewer fruits per plant than plants with root herbivores only. Although the experimental plants faced major herbivore-induced growth changes, plant reproduction (seed set and weight per plant) was similar in all treatments, documenting their ability to effectively compensate for leaf and root herbivory.     

Sexual dimorphism and sex ratios of two Australian dioecious species of alpine pineapple grass, Astelia alpina var. novaehollandiae and Astelia psychrocharis (Asteliaceae)

Sexual dimorphism and male biased sex ratios have been predicted for dioecious plants experiencing the limited conditions for growth and reproduction found in many alpine environments. To test these predictions, the reproductive ecology of two congeneric, co-occurring, dioecious, clonal, species was examined in the subalpine and alpine zones of Kosciuszko National Park, southeastern Australia. Specifically, plant size (vegetative cover of plants in quadrats), floral display (number of flowers per inflorescence, number of inflorescences per quadrat) and sex ratios (proportion of females in quadrats with flowers) were examined in ten populations of Astelia psychrocharis (Asteliaceae) and nine populations of Astelia alpina var. novae-hollandiae (Asteliaceae). Sexual dimorphism did occur, with males having more flowers per inflorescence (106% more flowers for A.alpina males and 12% more for A.psychrocharis males compared to females) and more inflorescences per quadrat than females (78% more inflorescences for A.alpina males and 46% more inflorescences for A.psychrocharis males compared to females). Plant size did not differ between male and female quadrats of either species, nor were there male biased sex ratios. However, plant size was related to flowering status in A.psychrocharis with the 65 quadrats that did not flower having lower vegetative cover than the 175 flowering quadrats indicating that there may be a minimum size/ cover required prior to flowering in this species. For A.alpina, all but two of the 185 quadrats randomly sampled flowered. There was no effect of altitude on plant size and very little effect of altitude on floral display for either species, apart from a slight increase in the number of inflorescences per quadrat with increasing altitude for A.psychrocharis, and slight decrease in number of flowers per inflorescence with increasing altitude for A.alpina females.     

Tillering in grain sorghum over a wiide range of population densities: modelling dynamics of tiller fertility

The prediction of tillering is poor or absent in existing sorghum crop models even though fertile tillers contribute significantly to grain yield. The objective of this study was to identify general quantitative relationships underpinning tiller dynamics of sorghum for a broad range of assimilate availabilities. Emergence, phenology, leaf area development and fertility of individual main culms and tillers were quantified weekly in plants grown at one of four plant densities ranging from two to 16 plants m(-2). On any given day, a tiller was considered potentially fertile (a posteriori) if its number of leaves continued to increase thereafter. The dynamics of potentially fertile tiller number per plant varied greatly with plant density, but could generally be described by three determinants, stable across plant densities: tiller emergence rate aligned with leaf ligule appearance rate; cessation of tiller emergence occurred at a stable leaf area index; and rate of decrease in potentially fertile tillers was linearly related to the ratio of realized to potential leaf area growth. Realized leaf area growth is the measured increase in leaf area, whereas potential leaf area growth is the estimated increase in leaf area if all potentially fertile tillers were to continue to develop. Procedures to predict this ratio, by estimating realized leaf area per plant from intercepted radiation and potential leaf area per plant from the number and type of developing axes, are presented. While it is suitable for modelling tiller dynamics in grain sorghum, this general framework needs to be validated by testing it in different environments and for other cultivars.     

Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata

Herbivores may damage both leaves and reproductive structures, and although such combined damage may affect plant fitness non-additively, this has received little attention. We conducted a 2-year field experiment with a factorial design to examine the effects of simulated leaf (0, 12.5, 25, or 50% of leaf area removed) and inflorescence damage (0 vs. 50% of inflorescences removed) on survival, growth and reproduction in the perennial herb Arabidopsis lyrata. Leaf and inflorescence damage negatively and independently reduced flower, fruit and seed production in the year of damage; leaf damage also reduced rosette size by the end of the first season and flower production in the second year. Leaf damage alone reduced the proportion of flowers forming a fruit and fruit production per plant the second year, but when combined with inflorescence damage no such effect was observed (significant leaf × inflorescence damage interaction). Damage to leaves (sources) caused a greater reduction in future reproduction than did simultaneous damage to leaves and inflorescences (sinks). This demonstrates that a full understanding of the effects of herbivore damage on plant fitness requires that consequences of damage to vegetative and reproductive structures are evaluated over more than 1 year and that non-additive effects are considered.     

On the Relationships of Net CO(2) Assimilation and Leaf Expansion to Vegetative Growth in Lycospersicum esculentum, var Jubilee

Relationships between net plant CO₂ exchange rate (CER) and canopy development were examined in `jubilee' tomato over the initial 4 weeks of vegetative growth. A comparison was made between two plant groups that were alternatively exposed to 200 or 800 microeinsteins per square meter per second midday irradiation to establish a differential in net CER. Plants exposed to higher irradiation demonstrated a 2- to 4-fold greater net photosynthetic rate per leaf area and 100% average higher net CO₂ assimilation rate/plant· day. However, leaf-stem growth differed by <50% suggesting a poor relationship to CER. Leaf area growth rate (LAGR) of individual leaves appeared closely related to CER during initial leaf expansion but a greater function of order of emergence in successive leaf growth. LAGR on a per plant basis increased linearly with leaf dry weight but appeared more limited by factors determining maximum leaf enlargement and rate of new leaf development. Net CO₂ assimilation/leaf area and leaf starch consistently declined with time while net CO₂ assimilation plant/day approached a constant rate following 2 to 3 weeks growth. Composite results suggested a simple relationship for sucessive growth where accumulated leaf carbohydrate in excess of 200 milligrams/plant·day could be expected to be partitioned to other plant segments.     

施肥对降香黄檀营养生长和生殖生长的影响

研究施肥对降香黄檀（Dalbergia odorifera T.Chen.）营养生长和生殖生长的影响,为不同经营目标的降香黄檀人工林培育提供技术支撑。本研究以8年生降香黄檀为对象,设置N（185.6 g N/株）、P（120 g P₂O₅/株）、K（120 g K₂O/株）、PK（120 g P₂O₅+120 g K₂O/株）、NPK（185.6 g N+120 g P₂O₅+120 g K₂O/株）以及不施肥（对照）等六个处理,调查施肥后盛花期内一年生新梢、叶、花的生长情况。结果表明：6个施肥处理间降香黄檀营养生长和生殖生长均差异显著（P<0.05）。N处理的营养枝率、营养枝复叶数和小叶宽分别比对照提高40.25%、21.75%和9.52%,花序直径和花序生物量则降低12.75%和48.63%,显示N肥能促进降香黄檀营养生长,抑制生殖生长,有利于大径材培育;P、PK处理的营养枝率较对照显著降低47.96%和46.84%,表明P肥和K肥能促进生殖生长,有利于良种选育;NPK处理能同时显著促进营养生长和生殖生长,其营养枝率、营养枝长度、营养枝复叶数、营养枝小叶长、宽和枝生物量比对照提高26.04%、68.16%、32.98%、15.20%、11.40%和83.60%,花序数量和花序生物量亦提高54.20%和49.84%。因此,在降香黄檀人工林培育实践中,可通过调整肥料的NPK配比（偏向N或PK）以实现营养生长或生殖生长调控之目的。     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.