Some environmental effects on the oil yield components of sunflower seeds

Summary and Conclusions Three sunflower varieties were tested at three sowing dates and three spacings, in a field experiment conducted under dryland conditions in Israel. Number of normal and empty seeds per head, weight of thousand seeds, kernel percentage, oil percentage and protein content were determined.Delay in sowing definitely decreased oil yield and its components except kernel percentage which was moderately increased.Protein percentage in kernels increased markedly at the late sowing.Narrowing of spaces between plants decreased the number of seeds per head and their weight, but did not affect composition of seeds. It caused an obvious increase of yield per unit of area.The number of empty seeds per head was not influenced by spacing but was markedly augmented by late sowing, due to a great increase of the central infertile part of the head.The total number of achenes seems to be determined during the vegetative period. Moisture or nutrient deficiencies during flowering and seed set may reduce the number of seeds, by increasing the infertile parts of the heads. Adverse moisture and temperature conditions throughout ripening interfere with the accumulation of oil and carbohydrates in seeds, thus reducing their weight and oil percentage.Kernel percentage was the character least affected by environmental variations, and may therefore be of considerable importance for breeding high oil yielding varieties.

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Zusammenfassung In einem unbewässerten Feldexperiment in Israel wurden drei Sonnenblumen-Sorten in drei Aussaaten zu verschiedenen Zeiten und in verschiedenen Pflanzabständen untersucht. Dabei wurde festgestellt: die Anzahl der normalen und der tauben Körner pro Korb, das Tausendkorngewicht, der Prozentsatz der Kerne, der Prozentsatz des Öl- und Protein-Gehalts.Die Verzögerung der Aussaat beeinträchtigte deutlich den ölertrag und die ihn beeinflussenden Faktoren. Der Prozentsatz des Proteins nahm bei später Aussaat beträchtlich zu.Die Verringerung der Abstände zwischen den Pflanzen beeinträchtigte die Anzahl der Körner pro Korb und ihr Gewicht, hatte aber keinen Einfluss auf die Zusammensetzung der Körner. Sie verursachte eine unverkennbare Zunahme des Ertrages pro Flächeneinheit.Die Anzahl der tauben körner pro Korb war nicht beeinflusst von dem Abstand der Pflanzen, aber auffallend vermehrt durch späte Aussaat infolge einer starken Zunahme des mittleren unfruchtbaren Teiles des Korbes.Es scheint, dass die Gesamtzahl derAchänen während der Vegetationsperiode bestimmt wird. Mangel an Feuchtigkeit oder Nährstoffen während Blüte- und Samenansatz können die Anzahl der Körner herabsetzen, infolge der Zunahme des unfruchtbaren Teiles des Korbes. Ungünstige Feuchtigkeits- und Temperatur-Bedingungen während der Reifezeit wirken störend auf die Bildung von Öl und Kohlehydraten in den Körnern und vermindern dadurch deren Gewicht und den Prozentsatz an Öl.Am wenigsten beeinflusst durch Verschiedenheit der Umweltbedingungen war der Prozentsatz der Kerne. Dieser kann daher von beträchtlicher Bedeutung sein für die Züchtung neuer Sorten mit hohem Öl-Ertrag.

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Résumé L'étude décrite ci-dessus porte sur trois variétés de tournesol, sémées à trois dates et suivant trois espacement différents. L'expérience a été réalisée en Israël dans des conditions non irriguées. Le nombre de graines normales et vides par capitule, le poids de mille graines, le pourcentage d'amondes, le pourcentage d'huile et de protéines ont été déterminé.Les semailles tardives réduisent nettement le rendement en huile et les facteurs correspondants, sauf le pourcentage d'amandes qui est accru modérément. Le pourcentage de protéines dans les amandes est accru de facon marquée par les semailles tardives. La réduction de l'espacement entre les plants fait décroitre le nombre de graines par capitule et leur poids, sans en affecter la composition; elle produit un accroissement certain du rendement à l'unité de surface.Le nombre de graines vides par capitule n'est pas influencé par l'espacement des plantes, mais il est accru de facon marquée en cas de semailles retardées; ceci est du à un fort accroissement de la partie contrale infertile des capitules.Le nombre total d'akènes semble être déterminé durant la période végétative. Il est possible qu'une déficience d'eau ou de matières nutritives pendant la floraison et pendant la formation des fruits, réduise le nombre de graines en provoquant l'accroissement de la partie infertile des capitules.Des conditions défavorables de température et d'humidité durant la période de maturation affectent l'accumulation d'huile et d'hyrates de carbone dans les graines en produisant une réduction de leur poids et de leur pourcentage d'huile.Le caractère le moins affecté par les variations du milieu fait le pourcentage d'amendes. Celui-ci peut par conséquent être d'une importance considérable dans l'amélioration de varietés à haut rendement en huile.

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with 2 figs.

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Part of the data presented herein were included in a dissertation submitted to the Senate of the Hebrew University, by MosheJ. Pinthus in May 1957.     

Density and relative frequency effects on competitive interactions and resource use in pea–barley intercrops

Intercropping advantages may be influenced by both plant density and relative frequency of the intercrop components. In a field study barley (Hordeum vulgare L.) and pea (Pisum sativum L.) were sole cropped and intercropped at three densities and with two relative frequencies when intercropped.Earlier seedling emergence gave barley an initial growth advantage, assessed using the relative efficiency index (REIc), whereas pea was in general more growth efficient once the initial growth phase had been passed. This reversal in relative growth efficiency along with the observation that early barley dominance did not appear to suppress pea growth indicates that differences in phenology played a role in shaping the prevailing dynamics. Whereas increases in plant density had a positive effect on the growth of pea, the growth of intercropped barley was severely limited by increases in density at the end of the growing period and more so in the pea dominated intercrop. At the final harvest land equivalent ratios (LER) of 0.9–1.2 express resource complementarity in almost all studied intercrops, complementarity that was not directly affected by changes in plant density or relative frequency.Intercropped pea did not increase its reliance on atmospheric nitrogen fixation compared to the pea sole crop. With respect to soil nitrogen uptake there were no effect of plant density but a strong effect of the relative frequency of pea in the intercrop, the greater the proportion the lower the uptake.Changes in the competitive strength of the pea and barley crop over the growing season had a marked effect on the proportion of pea in the final grain yields of the intercrops. At low and recommended density the proportions of pea and barley in the final grain yield was not markedly different from the expected proportions sown; however, at high density the suppression of barley strongly increased the proportion of pea in the final grain yield.Weed infestation levels decreased as density was raised and the suppressing effect of density was clearly stronger the greater the frequency of pea in the crop. Earlier germination and tillering ability of barley are seen as likely explanations of lower weed load in the barley dominated crop treatments.This study points at the potential of employing density and relative crop frequency as “regulators” when specific intercrop objectives such as increased competitiveness towards weeds or specific grain yield composition are wanted.     

Water deficit effects on caraway (Carum carvi L.) growth, essential oil and fatty acid composition

The Mediterranean region suffers of drought which affects plant behaviour regarding biochemical responses. Accordingly, the effects of water deficit on growth, essential oil and fatty acid composition of caraway (Carum carvi L.) seeds were investigated. Plants were treated with different levels of water deficit: control, moderate water deficit and severe water deficit. Plant growth (height, fresh and dry matter weight) was significantly reduced by severe water deficit. This last caused also important reductions of the seed yield and yield components. Drought decreased significantly seed total fatty acid contents and particularly the petroselinic ones whose proportions decreased significantly by 12.17 and 18.47%, in comparison with the control, under moderate water deficit and severe water deficit, respectively. Besides, moderate water deficit increased the essential oil yield (expressed as g/100 g on the basis of dry matter weight). The main essential oil constituents were carvone and limonene which showed an increasing of their contents under water deficit levels. Thus, water deficit induced a significant reduction in growth parameters and fatty acid content, and an increase in the essential oil compounds. These bioactive compounds have been required in many industrial products.     

加工工艺对菜籽油主要挥发性风味成分的影响

采用固相微萃取(Solid Phase Microextraction,SPME)方法顶空萃取富集预榨菜籽毛油、浸出菜籽毛油、一级菜籽油、冷榨菜籽油和脱皮冷榨菜籽油中的挥发性成分,经气相色谱-质谱联用仪(Gas Chromatography-Mass Spectrometry,GC-MS)检测和初步分析发现,硫甙降解产物、氧化挥发物(醛、醇、烃、酮等)、杂环类物质是构成菜籽油的主要挥发性风味成分;2-甲代-1-丙烯基-氰、5-己腈、1-丁烯基-异硫氰酸酯、苯基丙氰、2-苯基乙基异硫氰酸酯是主要硫甙降解产物;反2-反4-庚二烯醛、反2-反4-癸二烯醛、4-羟基-3,5-二甲氧基苯甲醛、壬醛等醛类物质是氧化挥发物中的主要成分。加工工艺对菜籽油风味影响显著,经高温蒸炒、压榨获得的预榨毛油中杂环类物质种类和相对含量明显高于其它菜籽油。毛油经脱胶、脱酸、脱色、脱臭、脱水等处理后,一级油中产生的醛、醇、酮、烃等氧化挥发物种类增多,相对含量提高;在一级油中未检测到硫甙降解产物。     

Frequency of symptomatic trees removal in small citrus blocks on citrus huanglongbing epidemics

Among the recommended measures for citrus Huanglongbing (HLB) management, the systematic elimination of symptomatic trees is the most argued and difficult to be accepted and accomplished by citrus growers. Elimination of recently affected HLB trees represents a short term yield loss and cost increase due to the need of frequent inspections and removal operations. This work aimed to evaluate the effect of different frequencies of inoculum reduction applied at individual citrus blocks scale (or local inoculum reduction) on HLB temporal progress. Eight experiments were carried out in new planted and older citrus blocks with 504–1290 trees/plot. In all experiments, inspections to detect symptomatic trees were done in a fortnightly or monthly frequency. The treatments of frequencies of local inoculum reduction varied from fortnightly to 6 months. Annual disease progress rate was estimated by logistic model for each plot. No difference on HLB progress rates among treatments was observed, except in experiments 1 and 3 where less frequent tree removal resulted in higher disease progress rate. This ineffectiveness of local inoculum reduction on the disease progress rate was explained by the higher weight of primary spread on HLB epidemics than the secondary spread within plots associated with small size and narrow shape of treated plots (except for experiments 1 and 3), high dispersal capacity of HLB-insect vector among plots and groves, and strong control of psyllid within the plots (except for experiment 1, with poor insecticide spray program). Also, the high amount of inspections to detect symptomatic trees before the eradication treatment, which reduced the escapes (asymptomatic and non visual detectable diseased trees) contributed for these results. It is important to note that these results were obtained with only small citrus plots (0.8–2.9 ha) and they cannot be extended to larger groves and farms amenable to HLB management by the symptomatic tree removal and vector control.     

茶叶籽油的加工工艺及其保健功效研究进展

茶叶籽油是一种纯天然高级木本可食用油脂,具有很高的营养价值和保健作用,其不饱和脂肪酸含量超过80%,维E含量丰富,具有降血脂、抗氧化及调节免疫功能、抗癌、美容护肤等保健功效。经初加工的茶叶籽油色泽深,带有苦涩味,需精加工。本文就茶叶籽油的理化特性、成分组成、加工工艺及其保健功能作一综述,以期为茶叶籽油的综合开发利用提供参考和依据。     

Inhibitory effects of Sage extract on the growth of enteric bacteria

Antibacterial activity of Sage extract at concentrations of 0.1, 0.05, 0.025, 0.0125, 0.00625, 0.003125, 0.00156, 0.0005 and 0.00025 g dL(-1) against Salmonella typhi, Shigella sonnei, S. flexneri, Proteus vulgaris, Staphylococcus aureus, ETEC Escherichia coli and Pseudomonas aeruginosa was evaluated. Susceptibility testing of bacterial strains against 18 antibiotics was also performed for comparison. The results showed that P. aeruginosa and ETEC E. coli were completely resistant to Sage extract even at concentration of 0.1 g dL(-1). Its antibacterial activity (0.1 g dL(-1)) against P. vulgaris, S. flexneri and S. sonnei was the same as nitrofurantoin and ampicilline respectively. Sage extract (0.1 and 0.05 g dL(-1)) exhibited the same effects as ampicilline and streptomycin against S. typhi. Its antibacterial activity (0.1, 0.05 and 0.25 g dL(-1)) against S. aureus was the same as ceftazidim, chloramphenicol, gentamycin, neomycin and nitrofurantoin and was more significant compared to streptomycin and vancomycin. The results suggest Sage can be considered as an alternative herbal in the treatment of infections caused by the above-mentioned bacteria.     

Some effects ofRhizoctonia solani on growth and yield of potatoes

Summary Below ground infection byRhizoctonia solani had little effect on the development of potato haulm. Severe infection caused an increase in the number of tubers initiated, but a reduction in the total weight of tubers. Tubers often formed in leaf axils of severely infected plants. It is suggested that these effects occur because assimilate production is not markedly affected by infection, but the compounds need to be redistributed when lesion development on the stolons blocks transport to the usual sinks.     

桉树叶水浸提液对香根草根系生长及部分生理指标的影响

为探讨香根草能否作为桉树人工林可选的林下经济植物,通过土培试验,研究桉树叶水浸提液对香根草根系生长及叶片部分生理指标的影响。结果表明:桉树叶水浸提液对香根草根系伸长和干重呈现出先促进后抑制的作用,但与对照相比差异不显著;香根草根系活力、叶绿素含量受桉树化感效应非常敏感,均随浓度的升高而呈现出先明显增加后显著下降的趋势;各浓度处理的香根草植株内丙二醛含量均高于对照,处理浓度≤40%时,差异不显著;高浓度≥60%,差异极显著。研究结果表明,香根草对桉树化感物质有较强的抗逆性,浓度≤40%桉树叶水浸提液促进了香根草的生长,仅在浓度≥60%时才表现为抑制作用。香根草有作为发展桉树人工林林下经济栽培植物的应用价值。     

Preventive effects of flaxseed and sesame oil on bone loss in ovariectomized rats

A study was designed to examine the effects of dietary flaxseed oil (FO) and sesame oil (SO) which are rich successively in n-3 and (n-9 and n-6) on biochemical parameters and histological status of bone. Sixty-four 90-day-old female wistar rats were randomly assigned to 6 groups: sham-operated rat (sham)+ control diets, ovariectomized rat (OVX) + control diets, OVX + 7% FO, OVX + 7% SO, OVX + 10% FO, OVX + 10% SO. After 4 weeks of treatments, rats were euthanized; blood and tissues were collected for analyses. Markers of bone formation which is alkaline phosphatase activity and markers of bone resorption which is tartrate resistant acid phosphatase activity were measured. Present results showed that OVX increased significantly ALP and TRAP activity and the examination of bone tissue showed disruptive and lytic bone trabeculae. Animals fed 10% FO and 10% SO of fat reduced these parameters and improved bone microarchitecture. Whereas, there was no improvement in biochemical and histological states in OVX rats that received 7% of PUFAs successively provided from FO and SO diets. In conclusion, our results are encouraging because they suggest that PUFAs intake may help to prevent osteoporosis associated with estrogens deficiency. However, further studies are needed to determine the mechanism by which a diet rich in n-3 or lignans modulate bone tissue.     

Microwave irradiation effects on the structure,viscosity, thermal properties and lubricity of soybean oil

Soybean oil is a highly valuable agricultural commodity for the United States. To further add value to soybean oil, chemical and physical modifications, as well as additives, have been extensively used to change the oil characteristics and properties, broadening the potential industrial applications. Heat treatments such as heat-bodying have been implemented to change soybean oil properties, but no research has studied the effects of microwave-irradiation on soybean oil structure and properties.Soybean oil (SBO) was heat-bodied (HB) or microwave-irradiated (MI). HB and MI (200–250 °C for 20–60 min) oil had similar Gardner bubble viscosity (B–C range). SBO that was HB or MI had increased viscosity compared with untreated SBO. ¹H NMR analysis showed no oxidation occurred for all treatments. However, HB and MI oil formed a cyclic ring structure with polymerization that most likely contributed to the increased viscosity. Pour point decreased from −9 °C for the untreated SBO, −15 °C for the HB, and −18 °C for the MI despite viscosity increases. Pour point anomaly is likely due to triacylglyceride cyclic ring formation. Pressurized DSC analysis showed higher oxidative stability for HB oil with even higher stability for MI oil. Compared with untreated SBO, HB and MI oil increased friction coefficient and decreased film percentage, whereas MI oil tended to leave larger wear scratches on the ball and disk during friction measurements. MI oil improved SBO cold-flow behavior, but reduced its potential as a lubricant.     

Tocotrienol and fatty acid composition of barley oil and their effects on lipid metabolism

Barley oil was extracted with hexane from the grain of a high oil waxy hull-les barley. Twelve male broiler chicks were fed corn-based diets with either 10% barley oil, 10% corn oil or 10% margarinead libitum for ten days. Total plasma cholesterol concentration of the chicks fed barley oil was 34% lower (p<0.05) than that of the chicks fed margarine. Plasma low density lipoprotein cholesterol concentration of chicks fed barley oil was 53% and 59% lower (p<0.05) than those of chicks fed corn oil and margarine, respectively. Plasma high density lipoprotein cholesterol and triglyceride concentration of the barley oil group were similar to those of the margarine but higher (p<0.05) than those of the corn oil group. Chicks fed the barley oil gained more (p<0.05) body weight than those fed the corn oil and margarine. Barley oil had an effect in suppression of TC and LDLC in chicks compared to margarine. Barley oil supressed LDLC but not HDLC in chicks compared to corn oil. A greater weight gain of the chicks fed barley oil suggested that these chicks had normally functioning digestion and absorption. -Tocotrienol and -tocotrienol content of the barley oil were 24 and 17 times greater, respectively, than those observed in the corn oil, while the same fractions were not detectable in the margarine. Polyunsaturated fatty acid content of the barley oil was more than threefold that of margarine. These data suggest that -tocotrienol and polyunsaturated fatty acids are hypocholesterolemic components in barley oil.Contribution No. J-2617, Montana Agricultural Experiment Station. This research was supported, in part, by grants from the Montana Wheat and Barley Committee, Great Falls, MT and Ross Laboratories, Columbus, OH.     

Comparative toxicity of selected insecticides to pea plants and growth promotion in response to insecticide-tolerant and plant growth promoting Rhizobium leguminosarum

Laboratory and field/pot experiments were conducted to determine the effect of two insecticides, fipronil and pyriproxyfen, on growth, symbiotic properties (nodulation and leghaemoglobin content), amount of N and P nutrients in plant organs, seed yield and seed protein of pea plants. In addition, the role of the most promising fipronil and pyriproxyfen tolerant Rhizobium leguminosarum strain MRP1 having plant growth promoting traits such as, production of phytohormones and siderophores, was also assessed in the presence and absence of both insecticides. Generally, fipronil and pyriproxyfen at the tested rates (recommended and higher doses) decreased the growth of both R. leguminosarum inoculated or uninoculated pea plants. Of the various concentrations of the two insecticides, pyriproxyfen at all concentrations in general, showed comparatively more severe toxicity to pea plants by decreasing plant biomass, symbiotic attributes, nutrients (nitrogen and phosphorus) uptake, seed yield and grain protein over the uninoculated control. The sole application of 3900 μg pyriproxyfen kg⁻¹ soil (three times the recommended dose) showed the highest toxicity and decreased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, seed yield and grain protein by 20%, 27%, 25%, 29%, 15% and 2% respectively, compared to the control. Interestingly, when the inoculant strain MRP1 was used with any concentration of the two insecticides, it significantly (P ≤ 0.05) increased the measured variables (plant dry weight, nodule numbers, dry nodule biomass, leghaemoglobin, nitrogen and phosphorus uptake, seed yield and grain protein) when compared to the plants grown in sandy clay loam soils treated solely (without inoculant) with the same individual treatment of each insecticide. For instance, three times the recommended dose of pyriproxyfen with strain MRP1 showed a highest stimulatory effect and increased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, seed yield and grain protein by 108%, 124%, 119%, 153%, 112% and 6% respectively, compared to the plants grown in soil treated solely with three times the recommended dose of pyriproxyfen.     

Fungal endophyte diversity in Paspalum and effects on plant growth

In natural ecosystems, plants appear to be in symbiosis with diverse fungal endophytes which can have impacts on plant communities. Paspalum is one of the most important grass genera in South American grasslands. The aim of this work was to determine the presence of fungal endophytes in two Paspalum species and evaluate their effects on plant growth. Sixty plant samples were collected for Paspalum notatum in a rangeland in northeastern Argentina, and the same number for Paspalum dilatatum in central Argentina. A triple-sterilization process was carried out by submerging small pieces of leaves and stems for the isolation of fungi from the collected plants. In order to identify endophytes, morphological characters and fungal sequences corresponding to the ITS (Internal Transcribed Spacer) region were analysed. A total of eight genera were identified: Acremonium, Alternaria, Aspergillus, Bipolaris, Cladosporium, Fusarium, Penicillium and Trichoderma. A greenhouse trial was conducted to determine the effects of fungal endophytes on growth. Trichoderma significantly increased relative chlorophyll content in P. notatum and Acremonium endophytes increased tiller number, and above- and below-ground biomass in P. dilatatum. The diversity of fungal endophytes that was present in P. notatum and P. dilatatum was described. In conclusion, some aspects of growth of these Paspalum species seem to be positively affected by Trichoderma and Acremonium.     

Profiling the effects of microwave-assisted and soxhlet extraction techniques on the physicochemical attributes of Moringa oleifera seed oil and proteins

There is a constant search for biomaterials from natural products like plants for food and industrial applications.The work embodied in this report aimed at investigating the effects of microwave-assisted and soxhlet extraction(MAE and SE) techniques on the functional physicochemical quality characteristics of Moringa oleifera seed oil and proteins extracts. M. oleifera seeds were ground to fine powders and oil was extracted by microwave-assisted and soxhlet extraction techniques using petroleum...     

Waterlogging effects on growth and yield components in late-planted soybean

A major agronomic problem in the southeastern USA is low yield of late-planted soybean [Glycine max (L.) Merr.]. This problem is aggravated by the adverse effect of waterlogging on crop growth. Our objectives were to identify soybean growth stages sensitive to waterlogging; identify yield components and physiological parameters explaining yield losses induced by waterlogging; and determine the extent of yield losses induced by waterlogging under natural field conditions. Greenhouse and field studies were conducted during 1993 and 1994 near Baton Rouge, LA, (30 degrees N Lat) on a Commerce silt loam. Waterlogging tolerance was assessed in cultivar Centennial (Maturity Group VI) at three vegetative and five reproductive growth stages by maintaining the water level at the soil surface in a greenhouse study. Using the same cultivar, we evaluated the effect of drainage in the field for late-planted soybean. Rain episodes determined the timing of waterlogging; redox potential and oxygen concentration of the soil were used to quantify the intensity of waterlogging stress. Results of the greenhouse study indicated that the early vegetative period (V2) and the early reproductive stages (R1, R3, and R5) were most sensitive to waterlogging. Three to 5 cm of rain per day falling on poorly drained soil was sufficient to reduce crop growth rate, resulting in a yield decline from 2453 to 1550 kg ha-1. Yield loss in both field and greenhouse studies was induced primarily by decreased pod production resulting from fewer pods per reproductive node. In conclusion, waterlogging was determined to be an important stress for late-planted soybean in high rainfall areas such as the Gulf Coast Region.     

Modeling the effects of light, carbon dioxide, and temperature on the growth of potato

This study examined the effects of light, temperature and carbon dioxide on the growth of potato (Solanum tuberosum L.) in a controlled environment in order to ascertain the best growing conditions for potato in life support systems in space. 'Norland' and 'Russet Burbank' were grown in 6-L pots of peat-vermiculite for 56 d in growth chambers at the University of Wisconsin Biotron. Environmental factor levels included continuous light (24-h photoperiod) at 250, 400, and 550 micromoles m-2 s-1 PPF; constant temperature at 16, 20, and 24 degrees C; and CO2 at approximately 400, 1000, and 1600 microliters L-1. Separate effects analysis and ridge analysis provided a means to examine the effects of individual environmental factors and to determine combinations of factors that are expected to give the best increases in yields over the central design point. The response surface of Norland indicated that tuber yields were highest with moderately low temperature (18.7 degrees C), low CO2 (400 microliters L-1) and high light (550 micromoles m-2 s-1 PPF). These conditions also favored shorter stem growth. Russet Burbank tuber yields were highest at moderately low temperature (17.5 degrees C), high CO2 (1600 microliters L-1) and medium analyses will be used to project the most efficient conditions for growth of potatoes in closed ecological life support systems (CELSS) in space colonies.     

The effects of temperature and fertilizer nitrogen on the spring growth of tall fescue and cocksfoot

A detailed study of the spring growth curves of two forage grasses, tall fescue and cocksfoot, over three successive years showed a large variability of growth over the vegetative phase. This variability was evident at levels of fertilizer N which were considered to be non-limiting (60 kg N ha^-1 in autumn plus 120 kg N ha^-1 in February).
At this level of N there was a relationship between yield in the vegetative phase and accumulated temperatures from the last cut in the autumn which was described by a regression common to the three years. The slope of this regression represents the potential growth of a variety. At a lower level of N a separate regression was needed in each year to relate growth to accumulated temperature.
Variation in spring growth was not related to accumulated net radiation. Growth in the reproductive phase was related to accumulated temperature and accumulated net radiation from the 10-cm ear stage.     

赤霉素对粤西香根草种子发芽动态的影响

采用100、200、300、400 mg/kg浓度的赤霉素（GA3）溶液,分别对7~12月采集的粤西香根草种子浸种处理8 h,研究不同浓度赤霉素处理对不同月份的粤西香根草种子发芽动态的影响。结果表明：7~10月采集的粤西香根草种子的发芽势、发芽率和发芽指数逐渐增加,而后11、12月的香根草种子则呈下降趋势;赤霉素浓度为100~400 mg/kg时均可促进香根草种子的萌发,其中100 mg/kg赤霉素处理10月的粤西香根草种子,其发芽势、发芽率和发芽指数最高,分别为12.00％、14.00％和15.51,但移栽成活率低。旨在为提高香根草种子的发芽率提供依据。