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.     

GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE)

All tillers of timothy ( Phleum pratense ) growing in sand culture were labelled at weekly intervals. At each of eighteen dates between June and December a sample of plants was harvested, and dry weight and leaf area were determined for each group of tillers.
Tiller production was continuous throughout the experiment. Only those tillers which appeared before the end of July were able to form inflorescences, but among them the proportion of tillers with ears decreased with increasing lateness of origin.
Dry weight per plant increased rapidly for the first 14 weeks, and then did not change significantly until the end of the experiment. The flowering tillers lost dry weight after seed maturation; vegetative tillers, although smaller in size, continued to increase in number and weight. Dry weight per inflorescences was greatest in the main stem and decreased in subsequent tillers.
Leaf area per plant rose to a maximum soon after ear emergence and then declined, largely because the loss in leaf surface sustained by the flowering tillers was not offset by a corresponding increase in the vegetative tillers. Leaf area ratio decreased at first rapidly but later more gradually, while net assimilation rate was relatively high until maximum leaf area was almost attained, but then fell continuously to negligible values by October. Relative growth rate decreased throughout the experiment.
Initially the growth of the plant was largely determined by the flowering tillers in which, in close resemblance to the cereal plant, leaf area ratio and relative growth rate declined continuously. Tillers which did not flower were successively smaller in size and, because of their later origin, were exposed to less favourable environmental conditions by the time they had increased sufficiently in number to affect the growth of the plant.     

GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE L.): IV. THE EFFECT OF NITROGEN, PHOSPHORUS AND POTASSIUM SUPPLY ON GROWTH DURING THE FIRST YEAR

In a sand-culture experiment lasting 21 weeks plants of timothy grown from seed were maintained at all combinations of three levels of nitrogen, phosphorus and potassium. The number and weight of tillers, leaves and ears, and the weight of roots, were determined at the end of the experiment, and for some of the treatments at intervals of 4 weeks. All three nutrients had significant effects, especially N which at its lowest level of supply tended to mask the effect of the other two elements. Potassium influenced tiller numbers least, especially those of primary tillers, but in the presence of high concentrations of N and P it had a large effect on leaf area and dry weight. Relative growth and net assimilation rates responded to varying nutrient supply only in the early stages of growth, so that in general variations in dry weight were associated with nutrient effects on leaf area.     

GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE L.)

During the first year of growth of timothy, variations in nitrogen supply affected the number of tillers and leaves, leaf area and dry weight, but had little influence on relative growth and net assimilation rates, except at very low levels of nitrogen. Differentiation and ear emergence occurred slightly earlier at high nitrogen and ear length was increased; there was also an increase in the proportion of fertile tillers among the total number produced after the first few weeks of tillering. The effect of nitrogen supply on the number, dry weight and ear length of early primary tillers was small but became larger in later tillers. Irrespective of the level of nitrogen supply, tillers had particularly high net assimilation rates during the first few weeks following their appearance.     

覆膜栽培下春小麦种群的生长冗余与个体大小不整齐性的关系

 增加有效分蘖数被认为是提高小麦(Triticum aestivum)产量的重要方法之一,但是小麦种群在生长进程中也会形成大量的无效分蘖,存在“生长冗余”。研究了覆膜栽培对两个春小麦种群中无效分蘖比率和收获指数的影响,并从植物个体大小不整齐性和生活史策略的种群生态学角度探讨其影响机制。与露地对照相比,覆膜栽培能显著提高春小麦产量(+38.5%);产量的提高源于地上部分生物量（+44.7%）的显著增加。但是, 覆膜种群的繁殖分配（穗重/地上部分生物量,-5.2%）和收获指数(-4.5%)显著降低;在几个主要生     

放牧干扰对根茎冰草无性系种群年龄结构的影响

根茎冰草（Agropyron michnoi)是典型的无性系禾草。在松嫩平原,根茎冰草的分蘖节最老为４龄,可存活５个年度。不同季节的放牧干扰可导致根茎冰草无性系种群分蘖株的年龄结构发生变化,全年放牧样地和夏秋休牧样地均为稳定型年龄结构,两个冬季放牧样地均为增长型年龄结构。１龄分蘖株的生产力和营养繁殖力力均最大。４龄分蘖株均已丧失了营养繁殖力。营养繁殖芽的年龄结构可以更好地预测预报无性系种群和群落的未来。全年放牧可保护稳定型年龄结构,冬季放牧可保持增长型年龄结构,夏秋休牧可使种群发展为增长型年龄结构,两个冬季放牧样地将仍然保持单优势种群落,全年放牧地将仍为混生群落,夏季林牧样地具有向着单优势种群落演替的潜在趋势。     

高产优质早籼稻品种粤香占的生长发育特性

1998年早季在广东省农业科学院水稻研究所内,观察研究了粤香占的部分形态生理特性,结果认为这个常规稻新品种属高收获指数型,收获指数达0.6以上,而且是早季稻早熟种,其从播种到始穗历期为84 d。这个品种的生育前期生长优势较强,具有叶鞘/叶片长度比值小、LAI和干物质增长快、有效分蘖数量多的特点。     

THE EFFECT OF RUBIDIUM SULPHATE AND PALLADIUM CHLORIDE ON THE GROWTH OF PLANTS

1. Comparisons have been made between the action of rubidium sulphate and palladium chloride on the growth of barley, wheat, oats peas and beans in complete nutrient solutions.
2. Over a wide range of concentrations rubidium sulphate was not found to exercise either a beneficial or a harmful action on the growth of any of the species tested. The germination of the seeds was likewise not affected.
3. No benefit was derived from palladium chloride , but at a comparatively low concentration a harmful action occurred which became more intense with increasing concentration. Stunting of the main root and laterals was a characteristic feature of this toxicity. With the lower concentrations the check was temporary, and the roots eventually made normal growth, as good as that in the control plants. With increasing amounts of pallahum chloride the poisoning effect became more persistent, until a concentration was reached which did not allow of any root or shoot recovery.
4. The tolerance of palladium varies with the species, as was indicated b. the measure of recovery. Barley appeared to be the least, and oats the most sensitive of the three cereals tested. Peas responded at much the same concentrations as barley, but broad beans made so complete a recovery from the initial checking that the dry weights were ultimately not reduced even by the strongest concentration tested, the plants being indistinguishable from the controls.
5. The effect of palladium poisoning was similar whether the seeds were germinated in the presence of palladium or whether the seedlings were not introduced to it until they were about a week old.     

GROWTH AND PRODUCTION OF LAMINARIA LONGICRURIS (PHAEOPHYTA) POPULATIONS EXPOSED TO DIFFERENT INTENSITIES OF WATER MOVEMENT1

Blade elongation was compared in two populations of Laminaria longicruris de la Pylaie in Shag Bay, Nova Scotia, Canada; one population was exposed to and the other sheltered from high intensity water movement. The maximum and minimum elongation rates were similar for the two populations, but the sheltered coast plants grew more rapidly during 8 mo of the year. Measurements of internal inorganic nitrogen (NO₃^?+ NO₂^?) reserves and dry organic weight indicated that low concentrations of dissolved nutrients in summer and low levels of illumination in fall and winter were more limiting to growth at the exposed site than the sheltered site. Transplant experiments provided evidence that morphological differences between the exposed and sheltered coast plants accounted at least partially for their different responses to varying nutrient conditions and light levels. It is concluded that lower productivity of the exposed coast population is the result of adaptation to high intensity water movement.     

THE GROWTH AND MINERAL COMPOSITION OF THREE SPECIES OF SPERGULARIA AS AFFECTED BY SALINITY AND NUTRIENTS AT HIGH SALINITY

The effects of salinity on the growth of three species of Spergularia and the effects of some levels of different nutrients on the growth and mineral composition of the three species under high salinity were investigated in sand culture. In response to the effects of salinity, S. marina and S. rupicola behaved like true halophytes in terms of survival, mean dry weight and plant part weight ratios. Spergularia rubra also behaved like an ecological halophyte in terms of dry weight but in terms of survival, it behaved like a glycophyte. The poor growth exhibited by the halophytes, S. marina and S. rupicola under high salinity condition was significantly reversed with the addition of most nutrients, while the glycophyte, S. rubra showed no favorable response, rather the combination of some nutrients further reduced its growth. The increased growth in S. marina was as a result of increased root growth while in S. rupicola it was as a result of increased root and stem growth. High salinity conditions resulted in a marked reduction in calcium and potassium content and an increase in sodium and chloride content of leaves of the species. Addition of many of the nutrients to plants under high salinity condition generally resulted in increased sodium, calcium, potassium, and magnesium content of leaves, except that the addition of phosphate resulted in decreased amounts of calcium and magnesium. Results are discussed in relation to the salt tolerance of the species and how the supply of nutrients to these species in their natural habitats might help them overcome high salinity problems.     

ECOLOGY AND NATURAL HISTORY OF IRIDAEA CORDATA (GIGARTINALES,RHODOPHYTA) GROWTH1

The in situ growth, maturation and senescence, of central California Iridaea cordata (Turner) Bory was studied. This ontogenetic progression was quantified by measuring development and growth of: i) individually tagged blades, and ii) populations of blades within cumulative (1-yr duration) and seasonal experimental plots. Greatest growth and longest life span were exhibited by winter-spring initiated blades, and were correlated with a rapid increase, in irradiance, but not with either seawater temperature or nutrients. Tagging studies showed that reproductive maturation and senescence of blades occurred throughout the year, irrespective of date tagged, growth rate or size. Moreover, the majority of blades continued to elongate following maturation, and some matured within 3 mo of initiation at all seasons but winter. At the population level maturation took place primarily during summer-autumn when 90 ±2% of the population was mature. The majority of the population senesces or “dies back” during autumn-winter. It is concluded that in situ, the blades are derived almost totally via vegetative means involving perennation. This indirectly suggests that sexual reproduction or the success of sporeling development are marginal. Additionally, the species is perennial with annually deciduous blades, characterized by both rapid growth and maturation.     

鱼腥藻提取液对水稻生长发育和产量的促进作用

以田间小区试验和大区产量直接对比的方法研究了鱼腥藻提取认对水稻幼苗生长和产量以及产量构成要素的影响,并探讨了方便有效且适宜于大田使用的方法。用藻液处理后水稻幼苗增高,根数、根长增加,分蘖能力增强,秧龄提前,叶面积明显加大。水稻成熟后除株高比对照略有下降外,各项产量构成要素如粒数、粒重、有效分蘖数、植株干重、千粒重、穗长等都优于对照组,但增产幅度随水稻品种和处理方式不同而异。大田使用时以１％鱼腥藻提     

SEX RATIOS,MORPHOLOGY AND GROWTH OF THE AFRICAN BUCK DUCK

Frost, P. G. H., Ball, I. J., Siegfried, W. R. & McKinney, F. 1979. Sex ratios, morphology and growth of the African Black Duck. Ostrich 50:220-233.

Black Ducks Anus sparsa were trapped regularly in the Eerste River Valley near Stellenbosch, South Africa. The sex ratio of adult Black Ducks did not differ significantly from parity. Males were larger and heavier than females and also had proportionately larger wing spurs which are used when fighting over mates and territories. Body mass fluctuated seasonally, being lowest during summer and highest in autumn-winter. In the southwestern Cape breeding took place from July to December after the peak of the early winter rains. Ducklings hatched when waters were dropping and there was an increase in the emergence of aquatic insects. The growth rate of ducklings in the Eerste River Valley was severely retarded compared with that of ducklings reared in captivitly. Black Ducks moulted their body feathers twice a year, the moults corresponding to the pre- and post-nuptial moults of northern hemisphere waterfowl. Moults were not accompanied by any change in plumage coloration. Body and rectrix moult took more than five weeks to complete while remex replacement required about 30 days. Males began wing moult about a month earlier than females which delayed moulting until after their young had been reared. Forty-six percent of Black Ducks trapped had noticeable plumage aberrations; individual recognition among Black Ducks appears to be an important element in their social behaviour.     

水分胁迫下盆栽冬小麦根系生长与苗系生长及某些生理特性的关系

水分胁迫下,盆栽冬小麦根干重和根长密度呈直线正相关。鉴于根长密度反映了土壤中根系最活跃的部分［５］,是研究植物根系吸收水分和养分的最优参数之一［６］,本文用之研究了它与地上部生物量、净同化速率、叶水势和叶片相对含水量、气孔阻力和蒸腾速率的关系。结果表明,根长密度与净同化速率和地上部干重呈直线负相关,与叶水势和叶片相对含水量呈直线正相关;与气孔阻力呈直线负相关,与蒸腾速率呈直线正相关。为实验室进行冬小麦生长控制与生理特性控制提供了一定的基础。     

KINETICS OF NUTRIENT UPTAKE AND GROWTH IN PHYTOPLANKTON1

Microscopic algae can grow rapidly in natural waters that are extremely low in essential macro and micro nutrients. Yet, their nutrient uptake systems exhibit only mediocre nutrient affinities, the saturation constants being often 10–1000 times the (estimated) ambient concentrations. The large difference which exists between the saturation constants for growth (K_u) and short term uptake (K_p) are due to the acclimation capabilities of the organisms. Over the acclimation range, K_u, to K_p the algae can maintain maximum growth rate by modulating both their internal nutrient quotas (Q) and their maximum short term nutrient uptake rates (P_max) in response to variations in external nutrient concentrations. The commonly assumed hyperbolic relationships for steady growth and uptake (viz “chemostat theory”) are coherent with a hyperbolic expression for short term uptake including a variable maximum (P_max). The ratio of the saturation constants for growth and uptake is then directly related to the extreme in quotas and maximum uptake rates: K^μ/K^ρ= Q^min/Q^maxρ^max/ρQ^max. This result is applicable even when the exact hyperbolic laws are not. Published data on Fe, Mn, P and N limitation in algae are generally in accord with the theory and demonstrate a wider acclimation range for trace than for major nutrients.     

KINETICS OF NUTRIENT UPTAKE AND GROWTH IN PHYTOPLANKTON1

Microscopic algae ran grow rapidly in natural waters that are extremely low in essential macro and micro nutrients. Yet, their nutrient uptake systems exhibit only mediocre nutrient affinities, the saturation constants being often 10–1000 times the (estimated) ambient concentrations. The large difference which exists between the saturation constants for growth (K_μ) and short term uptake (K_ρ) are due to the acclimation capabilities of the organisms. Over the acclimation range, K_μ to K_ρ, the algae can maintain maximum growth rate by modulating both their internal nutrient quotas (Q) and their maximum short term nutrient uptake rates (ρ_max) in response to variations in external nutrient concentrations. The commonly assumed hyperbolic relationships for steady growth and uptake (viz “chemostat theory”) are coherent with a hyperbolic expression for short term uptake including a variable maximum (ρ_max). The ratio of the saturation constants for growth and uptake is then directly related to the extreme in quotas and maximum uptake rates: K_μ/K_ρ= Q_min/Q_max·ρ^lo_max/ρ^hi_max. This result is applicable even when the exact hyperbolic laws are not. Published data on Fe, Mn, P and N limitation in algae are generally in accord with the theory and demonstrate a wider acclimation range for trace than for major nutrients.     

不同放牧强度下矮嵩草（Kobresia humilis）无性系分株种群的动调

以矮嵩草无性系分株和分蘖分别作为其种群的基本单元,对不同放牧强度下种群的动态与调节进行了研究。结果表明：随着放牧强度的增加,每分株的分蘖数、叶片数及分株个体地上生物量均增加．分蘖死亡率和叶片死亡率在各处理间差异不显著。分蘖死亡率的高峰出现在生长季末,叶片死亡率在生长初期和末期较高,而且都不属于密度制约性的死亡。矮嵩草多重种群结构水平的数量调节是由最外层次（叶片层次）的数量变化引起的,进而影响到较内层次上结构单元的大小和数量。     

冬小麦(Triticum aestivum)分蘖冗余生态学意义以及减少冗余对水分利用效率的影响

通过盆栽试验,以旱作冬小麦(Triticum aestivum)为材料,分别在拔节和抽穗期对分蘖进行人工干扰,来模拟不可预测的自然干扰,对冬小麦分蘖冗余的生态学意义以及减少这些冗余对水分利用效率影响进行研究.设置3个处理:从拔节期开始剪去所有小的分蘖,仅保留主茎和一个大的分蘖(A);在拔节期剪去主茎和两个大的分蘖,保留所有小的分蘖(B);在孕穗期剪去主茎和有效分蘖,保留无效分蘖(C).没有被干扰的植物作为对照(CK).通过花期测定叶片的叶绿素含量、叶绿素荧光参数、气孔导度和蒸腾速率等生理指标来评价植物的生理与生化活性.结果显示,在拔节期和抽穗期去除主茎和大蘖后,无效分蘖的生理活性被激活,开始执行有效分蘖的功能.到花期时,这些无效分蘖已经在生理活性上满足了补充和替代有效茎的要求.虽然株高和穗的整齐度、穗数和产量显著下降,但并没有防碍小麦的繁衍子代,因此,正是这些由早期"无效分蘖"补充而来的有效茎,避免了小麦绝种的风险.而在拔节期去除无效分蘖后,对小麦产量没有显著影响,但提高了水分利用效率,和对照相比水分利用效率提高了10%.因此,可以认为小麦在分蘖上存在着对水分利用不利的生长冗余,减少这些冗余有望节约用水、提高作物的水分利用效率.     

ABSORPTION OF NUTRIENTS AND PLANT GROWTH IN RELATION TO HYDROGEN ION CONCENTRATION

The absorption of nutrients depends to a large extent on the reaction of the substrate. At maximal growth the intake of salt is at minimum. Different ions are very differently affected. The intake of water is independent of the absorption of salts.     

EXPERIMENTAL STUDIES OF THE EVOLUTIONARY SIGNIFICANCE OF SEXUAL REPRODUCTION. V. A FIELD TEST OF THE SIB-COMPETITION LOTTERY HYPOTHESIS

Sexually and asexually derived tillers of Anthoxanthum odoratum were planted directly in the field to test the hypothesis that competition among groups of sexual and asexual siblings favors the maintenance of sexual reproduction in populations. The results showed a substantial fitness advantage for sexual tillers. However, in contrast with the models, the advantage of sex did not increase with increasing numbers of colonists in the patch, there were multiple survivors among colonists, and an advantage was observed even for singly planted tillers. When a truncation-selection scheme was imposed ex post facto on the data, the relative performance of sexual tillers was similar to that predicted by the Bulmer (1980) model, suggesting that sib-competition models fail due to the violation of the assumption of truncation selection. The advantage of sex was not correlated with the presence of other species, total percentage cover, or species diversity, although sites where sex was favored were physically clustered.