Hydrotime analysis of Lesquerella fendleri seed germination responses to priming treatments

Lesquerella fendleri seeds contain industrial oil, which is increased under arid environments. In such environments, the water needed for germination is available for only a short time, and consequently, successful crop establishment depends not only on rapid and uniform germination of the seedlot, but also on its ability to germinate under low water availability. All of these attributes can be analyzed through the hydrotime model (HT). Priming is a method to improve the speed and uniformity of germination. This technique reduces the hydrotime constant (θ_H) and sometimes displaces the base water potential (ψ_b(50)). This would increase the ability of the seed to germinate under low water availability.The objective of this work was to improve (i) the velocity and uniformity of germination and (ii) the ability to germinate under low water availability condition, in seeds of L. fendleri. We also intended to analyze and model changes in the physiological behaviour of the seedlot caused by the application of the priming treatment with seeds sown both in Petri dishes and containers with soil placed in the field.Seeds were subjected to priming in Petri dishes with a solution of polyethylene glycol (PEG) at 5 (P5) or 20 °C (P20). One-half of the seedlot was used for determination of hydrotime parameters by incubation in Petri dishes at 10, 20, and 30 °C, and in water or PEG solutions calibrated to obtain different ψ_a. The remaining one-half of the seedlot was sown in soil containers. Three different water availability treatments were imposed, field capacity or control, 75%, and 50% of the field capacity with the P5, P20, and untreated seeds. The P20 and P5 seeds germinated faster and more uniformly than the untreated (control) seeds under laboratory and field condition. The HT model analysis revealed that the θ_H constant had been reduced and ψ_b(50) had been shifted towards more negative values in both the P20 and P5 seedlots. This behaviour was consistent with the higher germination percentage attained by the P20 and P5 seeds in the field conditions under reduced water availability (i.e., 75 and 50% of field capacity) compared with that exhibited by the untreated seeds under the same situations.     

Rheological characterization of jet-cooked Lesquerella fendleri seed gum and cornstarch solutions

Lesquerella is a potential new seed crop that contains hydroxy fatty acid triglycerides and approximately 15% seed coat gums. The polysaccharide gum of the Lesquerella fendleri seed was isolated and jet-cooked with cornstarch in a series of laboratory experiments to investigate the viscoelastic properties of gum-modified starch solutions. The Lesquerella gum was combined with cornstarch at 1, 5, and 10% levels to produce a jet-cooked and drum dried material with potential application as a thickening or suspension agent. Flow curves were determined for 1% solutions of jet-cooked starch and gum combinations. All materials investigated were biodegradable and exhibited positive thixotropic behavior.     

Effects of soil water deficit at different growth stages on rice growth and yield under upland conditions. 2. Phenology,biomass production and yield

Phenological development, shoot dry matter production, grain yield and yield components of rice were examined in relation to drought occurring at various stages of growth. Rice was sown three or four times at three-week intervals in the field in each of two years, and performance in three stress trials was compared with that in corresponding irrigation trials, with the aim of quantifying the response of the crop to water stress of 23–34 days' duration developing at different growth stages. When drought occurred during vegetative stages, it had only a small effect on subsequent development and grain yield. The reduction in yield of up to 30% was due to reduced panicle number per unit area in one trial, and reduced number of spikelets per panicle in another. The effect of water stress on yield was most severe when drought occurred during panicle development. Anthesis was delayed, the number of spikelets per panicle was reduced to 60% of the irrigated control and the percentage of filled grains decreased in one crop to zero. This decrease in grain yield to less than 20% of the control was associated with low dry matter production during the drought period as well as during the recovery period following the drought. When drought occurred during grain filling, the percentage of filled grains decreased to 40% and individual grain mass decreased by 20%. The effect of stress was also related to its severity during grain filling. Stress at this stage hastened maturity. The results suggest that variation in yield components due to water availability is related to the variation in dry matter production at particular growth stages. Results of a supplementary shading experiment show that the relationship between spikelet number per panicle or single grain mass and crop growth rate was the same, whether growth rate was varied by availability of soil water or solar radiation. Filled-grain percentage, however, was more sensitive to drought stress than shading when comparison was made at a similar crop growth rate.     

Plant water stress at various growth stages and growth and yield of soybeans

In the Southern High Plains of the U.S.A., where water for irrigation is being depleted, drought-tolerant crops are extensively grown under limited irrigation where less water is applied than is required for potential evapotranspiration and maximum yield. This study was conducted (1) to determine the effects of plant water stress at various growth stages on growth and yield of soybeans [Glycine max (L.) Merr.] and (2) to assess the adaptability of the soybean plant to limited irrigation in the stressful climate of the Southern High Plains. The 3-year study was conducted on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Soybeans (‘Douglas’, indeterminate, maturity group IV) were grown with different irrigation treatments designed to subject the plants to water deficits at different growth stages. Stress initiated during R1 (early flowering) or R2 (full bloom) and extending to R3 (beginning pod development) reduced seed yields by 9–13%. But, when stress was extended to R4.5, yields were reduced by 46%. Stress beginning at R3 and extending to R4.5 reduced yields by 19%. Stress imposed at R5 and relieved at R6 reduced yields 15% in one year and 46% in a more stressful year. Stress imposed at R5 and extending to the end of the growing period (5 weeks) reduced yields by 45% in the less-stressful year and by 88% in the other. Stress throughout the last 3 weeks of the growing period (beginning at R6) reduced yields by 21 and 65%, respectively, in the two years. Water-use efficiency was not increased under limited irrigation. Soybeans are amenable to limited irrigation under the stressful climate of the Southern High Plains, but their vulnerability to drought stress during seed development complicates management. They are more suited for limited irrigation than is corn (Zea mays L.) but are less suited than are grain sorghum [Sorghum bicolor (L.) Moench], cotton (Gossypium hirsutum L.) or wheat (Triticum aestivum L.).     

Functional properties of protein from Lesquerella fendleri seed and press cake from oil processing

This investigation determined the functional properties of protein in Lesquerella fendleri seed and press cake from oil processing. L. fendleri seeds were heat-treated at 82 °C (180 °F) during 120 min residence time in the seed conditioner, and then screw-pressed to extract the oil. Unprocessed ground, defatted lesquerella seeds and press cakes were analyzed for proximate composition and protein functional properties. Protein from unprocessed lesquerella seed showed the greatest solubility (≥60%) at pH 2 and 10 and was least soluble (25%) at pH 5.5–7. Unprocessed lesquerella protein also had high surface hydrophobicity index (S_o), as well as, excellent foaming capacity and stability, emulsifying properties, and water-holding capacity (WHC) at pH 7. Protein solubility profile of the press cake showed up to 50% reduction in soluble proteins at nearly all pH levels, indicating heat denaturation during cooking and screw-pressing. Foaming capacity of the press cake protein decreased slightly, but foam stability was completely lost. Press cake protein also had markedly reduced values for S_o, emulsifying properties and WHC, further confirming lesquerella protein’s sensitivity to heat treatment.     

增效磷肥对花生生长、产量和磷利用率的影响

采用大田试验,在正阳县酸性砂姜黑土和清丰县石灰性砂质潮土区,研究了磷肥与不同增效剂（腐殖酸、 复合氨基酸和草酸）配施对花生生长、产量及磷肥利用率的影响。结果表明,85%常规施磷与腐殖酸、氨基酸和草 酸配施对花生产量的作用效果受土壤类型影响,砂姜黑土区,分别比85%常规施磷增产8.82%、4.66%和-1.68%,砂 质潮土区分别比85%常规施磷增产8.40%、3.18%和12.08%,砂姜黑土区和砂质潮土区分别以85%常规施磷+腐植 酸和85%常规施磷+草酸处理对花生生长和增产的促进效果最好。施磷增效剂也提高了花生磷积累量和磷肥利用 率,其原因在于磷增效剂促进了土壤难溶性磷组分转化为活性较高磷组分,与85%常规施磷相比,砂姜黑土区85% 常规施磷+腐植酸和砂质潮土区85%常规施磷+草酸处理的花生磷积累总量分别显著增加26.31%和22.89%,磷肥 表观利用率分别提高7.74%和4.99%,磷肥农学效率分别提高5.54 g/kg和5.39 g/kg。因此,酸性砂姜黑土区磷肥减 量15%配施腐殖酸,石灰性砂质潮土区磷肥减量15%配施草酸,可提高磷肥利用率,确保花生不减产,实现磷肥减 量增效目标。     

The effect of short periods of shading at different stages of growth on the development of tuber number and yield

Summary Shading potato plants at the beginning of tuber initiation for a period of 12 days reduced the rate of tuber formation and growth; but after the shades were removed tuber formation continued to give more tubers and the shaded plants eventually produced 30% more tubers than the unshaded, with similar yield. Shading for 12 days during the early stages of rapid tuber bulking had no effect on tuber number or survival, though bulking rate was temporarily reduced, leading to a reduction in final yield. These number results indicate that tuber number can be influenced by the weather during the period of tuber initiation.     

Water usage by potato plants at different stages of growth

Three groups of single-halm potato plants were tested for water usage at different stages of growth under growth chamber, greenhouse and field conditions by conducting 24-hour uptake studies at weekly intervals. Although the water usage was higher and more variable in the greenhouse and field than in the growth chamber because of varying environmental conditions during the 24-hour test periods, similar patterns were obtained. From emergence, the potato plant appeared to have four growth stages based on morphological development and water use. The young plant stage from emergence to tuber initiation is characterized by rapid growth, high transpiration rate per unit of plant material (essentially foliage), transpiration significantly correlated with the amount of foliage and a higher percentage of moisture being retained in the plant. The second stage is essentially a short transition stage of tuber initiation where top growth continues, transpiration levels off and a lower percentage of moisture is retained in the plant. The third stage is the tuber bulking stage where transpiration and water use remain relatively static because of non-expanding top growth and a lower percentage of moisture being retained in the plant during the bulking process. The final stage of senescence and tuber ripening is characterized by a marked reduction in water use primarily because of lower transpiration and loss of functioning foliage.     

Relationships between plant density,row spacing,depth of root penetration and water-use efficiency and the reproductive yield of dryland cotton

The influence of plant population and spacings on (a) extent and depth of root penetration and the rate of evapotranspiration of winter-stored water, (b) efficiency of water-use for reproductive yield, (c) earliness of maturity, and (d) decreased yield due to insect pest damage was investigated in cotton cultivars of two species,Gossypium hirsutum L. andG. barbadense L., during three growing seasons.The highest plant densities favored, mainly inG. hirsutum L. (Acala 1517 C), root penetration and increased water uptake up to 60 m³/1000 m². The maximum yield per unit area and water-use efficiency for production of seed-cotton was obtained with intermediate to dense plant populations. The intracultivar variations in water-use efficiency induced by plant spacings and densities ranged from 0.451 to 1.099 kg/m³ in Acala 1517 C and from 0.497 to 0.938 kg/m³ in Pima 32.Estimates of partial correlation indicated a closer dependence of yield of seed-cotton on the number of bolls per plant than on the boll weight. The degree and significance of the correlation with boll weight varied with plant density. It was also determined that the yield of seed-cotton per plant is greatly affected by the assigned soil area and volume distribution around it.The estimated yield regression curves indicated that yield of seed-cotton does not depend merely upon the plant density but is to a large extent affected by the type of spacing. In two-direction spacing variations, plant densities up to 150,000 plants/ha exhibited a symmetric parabolic relationship with yield of seeds and of lint. In Acala 1517 C, the maximum yield of lint (690 kg/ha) was estimated as obtainable at 107,790 plants/ha.Plant density interacted with cultivars in its effect on lint percentage. It considerably affected earliness (up to 30%) and the loss in yield due to damage inflicted byEarias insulana Boisd. The cultivars also responded differentially to the number of plants per hill. G. hirsutum cultivars, and in particular Acala 1517 C, exhibited a more favorable production ability under subtropical dryland conditions than didG. barbadense cultivars.

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Zusammenfassung Die Wirkung der Bestandesdichte — und Abstände auf (a) den Umfang des Wurzelwerkes und die Verwurzelungstiefe bei Baumwolle und auf die Evapotranspiration des während des Winters im Boden aufgespeicherten Wassers, (b) die Leistungsfähigkeit des Wassers für die Bildung der reproduktiven Pflanzenteile, (c) die Frühzeitigkeit der Reife und (d) den Ertragsverlust durch Schädlinge wurden unter subtropischen Trockenbedingungen bei Baumwolle-Sorten zweier Arten:Gossypium hirsutum L. undG. barbadense L. und zwar im Verlauf von drei Wachstumsjahren (1959–1962), untersucht.Die erreichten Ergebnisse bewiesen, daß der dichteste Pflanzenbestand, hauptsächlich inG. hirsutum L'Acala 1517 C die Wurzelvertiefung beförderte und die Wasseraufnahme bis 600 m³/ha erhöhte. Der Höchst-Ertrag je Einheitsfläche sowie die Leistungsfähigkeit des Wassers für die Erzeugung von Faser-und-Körnern wurde mit Pflanzenbeständen mittlerer (Tab. I, VII) und höherer, (Tab. I, Acala 1517 C) Dichte erreicht. Die von den Pflanzenbestand-und-Abständen beeinflußte Sorten-innerliche Schwankungen der Leistungsfähigkeit des Wassers erstreckten sich auf einem Bereich von 0.451–1.099 kg/m³, bei Acala 1517 C und 0.497–0.938 kg/m³ bei Pima 32.Die berechneten Teilkorrelationen ergaben daß ein engerer Zusammenhang besteht zwischen Faser-und-Körner-Ertrag und Anzahl der Kapseln je Einzelpflanze als der mit dem Gewicht der Einzelkapsel. Ausmaß und Signifikanz der lezterwähnten Korrelationen variierten je nach Dichte der Bestände (Tab. II). Fernerhin wurde festgestellt daß der Ertrag pro Einzelpflanze von der Verteilungsweise des ihr zugewiesenen Bodenfläche-und-Volumen weitgehend beeinflußt wird.Die berechneten Ertrags-Regressionskurven weisen daraufhin daß der Ertrag pro Flächeneinheit nicht nur von der Pflanzenbestandesdichte, sondern auch von der Art und der Richtung der Pflanzenbestände stark abhängig ist. Der durch zwei Richtung-Abstände versorgte Bestandesbereich von bis 150 Tausend Pflanzen je ha, ergab eine symmetrisch-parabolisches Verhältnis mit dem Ertrag von Faser, bzw. Körner (Ansicht 4 b,c). Für die Sorte Acala 1517 C wurde der Höchstertrag für eine Bestandesdichte von 107790 Pflanzen/ha errechnet.Weiterhin wurde eine bedeutende Wechselwirkung zwischen Sorten und Bestandesdichte festgestellt hinsichtlich: Prozentsatz der Faser, Frühzeitigkeit der Reife (bis zu 30%) und Ausmaß des durch Schädlinge, hauptsächlichEarias insulana Boisd., verursachten Ertragsverluste. Die erwähnten Sorten reagierten außerdem unterschiedlich je nach der Anzahl der Pflanzen pro Abstands-Stelle. G. hirsutum Sorten, und besonders Acala 1517 C, erwiesen eine bessere Eignung für subtropische Trockenwachstumsbedingungen alsG. barbadense Sorten.

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Résumé L'influence de la densité et de l'espacement de la population de plantes sur: (a) l'étendue de la profondeur de la pénétration de la racine et sur la quantité d'évapotranspiration d'eau accumulée dans le sol durant l'hiver, (b) l'efficacité d'usage d'eau pour la production reproductive, (c) la precocité de la maturité et (d) les degáts parasitaires à la récolte a été etudiée dans des conditions d'un climat subtropical sec sur des variétés du cottonier apartenants à deux espèces:G. hirsutum L. etG. barbadense L. au cours de trois saisons de culture (1959–1962).Les résultats obtenues ont montré que la population la plus dense des plantes (essai 2) a favorisé, surtout dansG. hirsutum L., var. Acala 1517 C, la pénétration de la racine et a augmenté la quantité d'eau absorbée — par 600 m³/ha. Tandis que le rendement maximum par unité de surface et la meilleure efficacité d'usage d'eau pour la production — de coton-graine — ont été obtenus avec des populations intermédiaires (Tables I, VII) jusqu'aux denses (Table I, Acala 1517 C).La variation intra-varietale en efficacité d'usage d'eau dérivant des variations en densités des plantes et en leurs espacements se range à 0.451–1.099 kg/m³ dans Acala 1517 C et à 0.497–0.938 kg/m³ dans Pima 32.Les évaluations de la corrélation partielle ont revelé que le rendement (en coton-graine) par plante dépend plutôt du nombre des capsules que de leur poids. Le degré de la dernière corrélation et sa signification statistique ont variés avec la densité des plantes. Il a été constaté également que le rendement (en coton-graine) par plante dépend grandement du mode da la distribution du sol en surface et en volume par rapport à la plante individuelle.Les courbes des régressions evaluées indiquent que le rendement en fibres, respectivement en graines, par unité de surface ne depend pas seulement de la densité des plantes, mais aussi dans une grande mesure, de la façon dont l'espacement des plantes est arrangé.Dans une rangée jusqu'à 150 milles plantes par ha, obtenue par l'espacement en deux directions, une relation parabolique symmétrique a été trouvé par rapport au rendement des fibres, respectivement des graines. Pour la variété Acala 1517 C le rendement maximum en fibre (690 kg/ha) a été evalué, avec 107,790 plantes par ha.Une interaction entre les variétés et les densités de plantes a en son effet sur le pourcentage de la fibre sur la precocité de la maturité (jusqu'à 30%) et sur le taux de la recolte endommagée par les parasites, et surtout par l'Earias insulana Boisd. Les variétés essayées ont réagi d'une manière différentielle sur le nombre des plantes par coteau.L'espèceG. hirsutum L., et spécialement l'Acala 1517 C, ont fait preuve d'une meilleure adaptation en culture sèche dans conditions subtropicales que l'espèceG. barbadense L.

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Contribution from The Volcani Institute of Agricultural Research (N.U.I. A.), Bet Dagan, Israel. 1969 Series; No. 1504-E.     

Study of water stress effects in different growth stages on yield and yield components of different rice (Oryza sativa L.) cultivars

A field experiment was conducted during 2001-2003 to evaluate the effect of water stress on the yield and yield components of four rice cultivars commonly grown in Mazandaran province, Iran. In northern Iran irrigated lowland rice usually experiences water deficit during the growing season include of land preparation time, planting, tillering stage, flowering and grain filing period. Recently drought affected 20 of 28 provinces in Iran; with the southeastern, central and eastern parts of the country being most severely affected. The local and improved cultivars used were Tarom, Khazar, Fajr and Nemat. The different water stress conditions were water stress during vegetative, flowering and grain filling stages and well watered was the control. Water stress at vegetative stage significantly reduced plant height of all cultivars. Water stress at flowering stage had a greater grain yield reduction than water stress at other times. The reduction of grain yield largely resulted from the reduction in fertile panicle and filled grain percentage. Water deficit during vegetative, flowering and grain filling stages reduced mean grain yield by 21, 50 and 21% on average in comparison to control respectively. The yield advantage of two semidwarf varieties, Fajr and Nemat, were not maintained under drought stress. Total biomass, harvest index, plant height, filled grain, unfilled grain and 1000 grain weight were reduced under water stress in all cultivars. Water stress at vegetative stage effectively reduced total biomass due to decrease of photosynthesis rate and dry matter accumulation.     

The effect of moisture stress at three growth stages on the yield,components of yield and processing quality of eight potato varieties

A study was conducted over a three year period in southern Alberta to establish the yield and quality responses of eight potato varieties-Atlantic, Conestoga, Norchip, Niska, Shepody, Ranger Russet (Idaho clone), Ranger Russet (Amisk clone) and Russet Burbank to a single transient moisture stress (-80 kPa) at three growth stages in crop development (early, midseason and late). Early and midseason moisture stress had the greatest negative impact (P<0.05) on tuber yield. Of the eight varieties, Atlantic and Conestoga appear to be particularly sensitive to stress at these two growth stages. Midseason stress also appeared to reduce specific gravity. A year x stress interaction (P<0.05) for fry color suggests that the influence of moisture stress on fry color can be modified by other environmental factors. The results of the study demonstrate the importance of maintaining adequate soil moisture at all stages during crop development.     

Grain yield,starch, protein,and nutritional element concentrations of winter wheat exposed to enhanced UV-B during different growth stages

In order to alleviate the damage of UV-B on plants, it is important to determine at which growth stages are plants more sensitive to enhanced UV-B. The objective of the study was to evaluate the effects of UV-B on wheat yield and quality during different growth stages. Enhanced UV-B during heading, flowering and the whole growth stages (UCK, from seedling to grain filling) decreased yield by 6.6, 4.4 and 9.6%, respectively. Protein content in grain was decreased by enhanced UV-B during flowering and UCK over the control. Amylose, amylopectin and total starch content were not affected by UV-B treatments. UCK treatment resulted in a decrease of nitrogen (N), phosphorus (P) and iron (Fe) concentrations, while zinc (Zn) and manganese (Mn) concentrations increased. Enhanced UV-B during tillering, heading and flowering stages reduced Fe concentration, but increased Mn, copper (Cu) and Zn (except for flowering) concentrations. The results indicated that the changes in wheat yield and quality induced by enhanced UV-B during the whole growth stage were probably from the effects of UV-B radiation during heading and flowering stages. Therefore, to better defend the damage of UV-B to wheat, some methods should be undertaken during heading and flowering stages.     

Tolerance of selected weed species to broadcast flaming at different growth stages

Organic producers rank weeds as the most important pests that limit their crop production. In order to optimize the use of propane flaming as a weed control tool, the objective of this study was to test tolerance of selected weed species to broadcast flaming performed at different growth stages. Six annual species, including one grass [barnyardgrass (Echinochloa crus-galli)] and five broadleaves [field bindweed (Convolvulus arvensis), kochia (Kochia scoparia), ivyleaf morning glory (Ipomoea hederacea), velvetleaf (Abutilon theophrasti) and Venice mallow (Hibiscus trionum)] were flamed at three growth stages with six doses of propane. The propane doses applied were 0, 12, 31, 50, 68 and 87 kg/ha. Flaming treatments were applied utilizing a custom built flamer mounted on a four-wheeler moving at a constant speed of 6.4 km/h. Species response to propane were described by log-logistic models based on visual injury ratings and dry matter (DM) for each weed species. Overall response to flaming varied among species, growth stage and propane dose. Broadleaf weeds were more susceptible to flaming than the grass regardless of the growth stage. A dose of 76 kg/ha of propane was needed to obtain 90% DM reduction for 7-leaf (L) barnyardgrass compared to much lower doses of 40, 49, 55, 56 and 51 kg/ha propane for 8-L bindweed, 6-L kochia, 10-L morning glory, 7-L velvetleaf and 5-L Venice mallow, respectively. Moreover, the tolerance of both grassy and broadleaf weed species to broadcast flaming increased with increase in plant size. A 90% DM reduction in velvetleaf was obtained with 42, 56 and 102 kg/ha of propane for 5-L, 7-L and 16-L stages, respectively. The tested broadleaf weed species were effectively controlled (90% DM reduction) with propane dose of 30–60 kg/ha when flamed at early growth stages (3-L to 14-L), while the same dose of propane provided only 80% DM reduction in barnyardgrass when flamed at vegetative stages (4-L to 7-L). It was not possible to obtain 90% DM reduction in barnyardgrass when flamed at flowering stage with the propane doses tested in this experiment.     

Effect of water stress at different development stages on vegetative and reproductive growth of corn

A field study was carried out from 1995 to 1997 in order to determine the effect of irrigation and water stress imposed at different development stages on vegetative growth, grain yield and other yield components of corn (Zea mays L.). The field trials were conducted on a silty loam Entisol soil, with Pioneer 3377 corn hybrid. A randomised complete block design with three replications was used. Four known growth stages of the plant were considered and a total of 16 (including rain fed) irrigation treatments were applied. The effect of irrigation or water stress at any stage of development on plant height, leaf area index, grain yield per hectare, as well number of ears per plant, grain yield per cob and 1000 kernels weight, were evaluated. Results of this 3-year study show that all vegetative and yield parameters were significantly affected by water shortage in the soil profile due to omitted irrigation during the sensitive tasselling and cob formation stages. Water stress occurring during vegetative and tasselling stages reduced plant height, as well as leaf area development. Short-duration water deficits during the rapid vegetative growth period caused 28–32% loss of final dry matter weight. Highest yields were observed in the fully irrigated control (VTCM) and the treatment which allowed water stress during the vegetative growth stage (TCM). Even a single irrigation omission during one of the sensitive growth stages, caused up to 40% grain yield losses during dry years such as 1996. Much greater losses of 66–93% could be expected as a result of prolonged water stress during tasselling and ear formation stages. Seasonal irrigation water amounts required for non-stressed production varied by year from 390 to 575 mm. Yield response factor (k_y) values (unitless parameter) relating yield loss to water deficits) obtained for the first, second and third experimental years were determined to be 1.22, 1.36 and 0.81, respectively.     

灵芝子实体不同生长阶段多糖与三萜类物质含量的研究

采用分光光度计法研究了灵芝芝蕾、芝柄、分化菌盖及成熟子实体等生长阶段的多糖与三萜类物质含量。结果表明,芝蕾发育阶段多糖含量最高,随着灵芝的生长发育,多糖含量逐渐降低;而三萜类物质含量则相反,芝蕾发育阶段最低,随着灵芝的生长发育逐渐升高,到成熟子实体阶段含量又略有降低。     

Cardinal temperatures for germination and early growth of two Lesquerella species

Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as ‘L. pallida aff.’ because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 °C, whereas L. fendleri germinated earlier at 18 °C, but grew faster at 22 °C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 °C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 °C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 °C) and optimal (22 °C) temperatures than non-dormant seeds (>7 °C and 28 °C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.     

Growth and yield response of common buckwheat (Fagopyrum esculentum Moench) to waterlogging at different vegetative stages

ABSTRACT

This study identified timing (1st, 3rd, or 5th leaf stage) and duration (1, 3, 6, or 10 days) of waterlogging treatment during the vegetative stage that had the most severe effect on yield and elucidated yield determining process. Yield was reduced the most by the waterlogging treatments at the 3rd leaf stage. Among stages, yield was significantly depressed, when the treatment duration was longer than 6 days. Seed weight of the 1st branches declined more under waterlogging treatments than did that of main stem and 2nd branches, accounting for approximately 55% of total seed weight in all treatments. On the other hand, the decline in node and branch numbers was more pronounced for 2nd branches than 1st branches at the ripening stage. The development of the 2nd branches during ripening did not contribute much to increase sink capacity. Development of the main stem and the 1st branches was almost complete until the full flowering stage and shoot dry weight did not increase from the full flowering stage to the ripening stage. Shoot dry weight at the full flowering stage was determined by both leaf number and net assimilation rate (NAR). Flower cluster number at that stage was significantly correlated with total seed weight. These results showed that the critical timing was at the 3rd leaf stage and the critical duration was longer than 6 days and indicated that maintenance of leaf number and NAR and development of flowers on the 1st branches until the full flowering stage would ensure the yield.

Abbreviations: NAR - net assimilation rate, SLA - specific leaf area, g_s - stomatal conductance.     

Genetic differences in water-use efficiency,stomatal conductance and carbon isotope fractionation in potato

Summary Potato (Solanum tuberosum L.) cultivars were grown in pots and containers under a rain shelter to examine differences in stomatal conductance, water-use efficiency, and carbon isotope fractionation. Conductance was measured on abaxial leaf surfaces with a steady state diffusion porometer. Carbon isotopic analyses were made with an isotope ratio mass spectrometer. Water-use efficiency (WUE) was obtained by dividing total dry matter production by cumulative transpiration. Significant genetic variation was observed for each trait. WUE was positively related to carbon isotope fractionation (¹³∈) and was inversely related to stomatal conductance. Carbon isotope analysis and porometry show potential as indirect screening methods to identify genetic differences in water-use efficiency.     

Carbon dioxide enrichment and temperature effects on cotton canopy photosynthesis,transpiration, and water-use efficiency

The objectives of this study were to evaluate effects of ambient and double ambient [CO₂] at a range of growing temperatures on photosynthesis, respiration, transpiration, water-use efficiency and dry matter accumulation of cotton plants (Gossypium hirsutum L., cv. DPL 50). In Experiment I, plants were grown outdoors until first bloom, then transferred into naturally lit growth chambers and grown for 22 days at 30/18°C with five CO₂ concentrations varying from 350 to 900 μl l⁻¹. In Experiment II, air temperatures were maintained at 20/12, 25/17, 30/22, and 35/27°C day/night during a 70-day experimental period with [CO₂] of 350 and 700 μl l⁻¹ at each temperature. Photosynthesis increased with [CO₂] from 350 to 700 μl l⁻¹ and with temperature. Plants grown at 35/27°C produced fewer bolls due to abscission compared with plants grown at optimum temperatures (30/20°C). At higher [CO₂], water-use efficiency increased at all temperatures due mainly to increased canopy photosynthesis but also to more limited extent to reduced canopy transpiration. Increased photosynthesis at higher [CO₂] resulted in greater dry matter accumulation at all temperatures except at 20/12°C. Respiration increased as dry matter and temperature increased. Plants grown at higher [CO₂] had less respiration per unit dry matter but more per unit area. These results indicate that future increases in [CO₂] are likely to benefit cotton production by increasing carbon assimilation under temperatures favorable for cotton growth. Reduced fruit weights at higher temperatures indicate potential negative effects on production if air temperatures increase as projected in a high-CO₂ world.     

Relationship of growth parameters and nutrients uptake with canola (Brassica napus L.) yield and yield contribution at different nutrients availability

A field experiment was conducted to evaluate the effect of different nutrients on canola (Brassica napus L.) growth parameters, nutrient uptake and ultimately on seed yield. For this purpose a split plot experimental design, with 10 treatments in 4 replications was carried out in 2004-2005, in silt-clay soil at Baiecola Agricultural Research Station, Mazandaran Iran. Canola seed yield, growth parameters (CGR, LAI, RGR and NAR), dry matter accumulation and HI and nutrient content of the leaf were examined. NPK fertilizers together with S and Zn, singly or in combination were applied. The results showed that at treatments T5 (NP), T8 (NPK), T9 (NPKS) and T10 (NPKZn) the higher seed yield (> 2600 kg ha(-1)) coincided with TDM > 880 g m(-2) the peak CGR > or = 13.9 g m(-2) day(-1) and the maximum LAI > or = 4.1. The higher seed yield at T5, T8, T9 and T10 coincided with higher concentrations of nutrients: N, P, K, S and Zn in leaf at flowering having > or = 3.40%, > or = 0.25%, > or = 1.53%, > or = 110 ppm and > or = 22.7 ppm, indicating substantial levels of translocation of nutrients at various stages of plant growth and higher number of pods per plant (> or = 179). Combined application of NPKZn at T10 resulted in maximum seed yield (3090 kg ha(-1)), coinciding with the maximum number of pods per plant (230), maximum TDM (1043 kg ha(-1)), maximum CGR (20.09 g m(-2) day(-1)) and maximum LAI (4.69).