Predicting Plant Height of Greenhouse Grown Crops with a Polynomial Growth Rate Model

A prediction model for the growth of plant height is developed, using polynomials in time to describe the growth rate. The growth rate is affected by forcing factors through the polynomial coefficients. A random slope model is used to describe the difference in growth rate for plants grown under similar conditions. Maximum likelihood estimates of model parameters are obtained and a selection procedure is employed to estimate the model complexity using Schwarz' bayesian criterion as a measure of predictive power. The procedure is applied to data sets for greenhouse grown poinsettias. The use of polynomials to describe the time effects on the growth rate makes the strategy versatile, and it can be used to predict the growth of many different crops. Many forcing factors of different types can be incorporated simultaneously in the model. Confidence of predictions are also quantifies, which is important when the results are applied in a practical situation, e.g. in climate control of commercial greenhouses.     

Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass × sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest.     

Studies of the Relationship between the Growth Rate of Young Plants and their Total-N Concentration using Nutrient Interruption Techniques: Theory and Experiments

Alternative assumptions about the utilization of stored nitrogenare used to derive two different models for predicting how thegrowth rate of both the whole plant and its shoot vary withtheir respective total-N concentrations following interruptionof the external N supply. Model 1 predicts that plant growthshould follow monomolecular kinetics after the supply is interrupted,with the resulting relative growth rates linearly related tototal-N concentration. Model 2 predicts that plants grow logisticallyonce N is withheld, with their relative growth rates varyinglinearly with the reciprocal of total-N concentration. The versionsof the models derived for the shoot are similar to those forthe whole plant, but include an additional term to allow fortransfer of N to the roots as deficiency increases. Tests ofthe models were carried out using data from N interruption experimentswith young cabbage and lettuce plants (containing either highor low nitrate concentrations) which were grown hydroponicallyin nutrient recirculating units. The results showed that therewas little statistical difference between the fits of the twomodels to the growth data over the range tested, but that model1 was unsatisfactory because the estimates of its parameterswere inconsistent with assumptions about the physiological processescontrolling growth, and because its predictions became unrealisticwhen extrapolated to conditions of acute N deficiency. Model2 did not suffer from either of these problems and provideda better mechanistic interpretation of the data, yielding predictionsthat were in close agreement with the observed relationshipbetween relative growth rate and total-N concentration for boththe whole plant and its shoot. The curvilinear form of thisrelationship for model 2 differs from the linear form of othermodels derived from measurements in experiments where therewas a continuing but restricted supply of external N to plants.This implies that the relationship between relative growth rateand total-N concentration may vary depending on whether or nota plant has to rely entirely on its internal reserves of N intimes of shortage. The results also showed that the size ofthese reserves governed the amounts of N transferred to theroots as deficiency developed. Transfer of N was greater incabbage than lettuce because of a greater capacity to adaptby increasing root growth at the expense of the shoot.Copyright1994, 1999 Academic Press Cabbage, deficiency, dilution, hydroponics, lettuce, model, nitrogen, nitrate, nutrient recirculation units, relative growth rate, shoot, total-N concentration, whole plant     

Rate of Increase in Size and Dry Weight of Individual Pods of Field Grown Soya Bean Plants

The dry weight of the whole fruit, the pod wall and an enclosedseed of randomly harvested soya beans is estimated from theexternal dimensions of the attached pod. The relations betweendimensions and dry weight are independent of cultivar and growthcondition and can be used on pods from 1 cm in length untilthe seeds reach their maximum fresh weight. Dimensions of tagged pods of three cultivars of field grownsoya beans differing in time to reach maturity were measuredevery 2–3 days from initial pod elongation until maturation.Dry weights for each pod were estimated from the dimensions,and the dry weight accumulation with time was fitted to thelogistic function to find the growth rate that best characterizedthe data for each pod. The final weight, the specific growthrate and the maximum growth rate of the whole fruit, the podwall and a single seed were subjected to analysis of variance. The most significant difference between pods of these cultivarswas the specific growth rate of individual seeds, which decreasedwith increasing maturity group. There were no differences ingrowth of the pod wall. However, most of the variation was betweenindividual pods within a cultivar, where the rate of dry weightaccumulation of the whole fruit, governed largely by the seedgrowth rate times the number of seeds, was highly correlatedwith the earlier growth of the pod wall. This suggests thatthe growth of individual whole fruit was determined early inpod development and was slightly influenced by factors appliedduring the period of rapid seed growth. Glycine max (L.) Merrill, Soya bean, seed growth analysis, specific growth rate     

Vegetable Plant Part Relationships. IV. An Interpretation of Growth Regulator Experiments with Root Crops

A quantitative scheme to describe the growth of plant partsduring the vegetative phase of development is extended to includethe concept of hormone directed transport. The expected effecton shoot/storage root d. wt relationships of a single àxternalapplication of a growth regulating chemical is investigatedusing this approach. The theory predicts that the resultingchange in the pattern of assimilate partitioning will modifythe underlying relationship between shoot and storage root weightsin a simple measurable fashion. The theory is inevitably oversimplifiedand speculative in parts but when a derived equation was fittedto data from an experiment in which gibberellic acid and daminozidewere applied to carrots, close agreement was found between thepredictions and experimental data. Daucus carota, carrot, shoot weight, root weight, gibberellic acid, N-dimethylamino-succinamic acid (daminozide), growth analysis     

Light Distribution and Photosynthesis in Field Crops

In a new model of light distribution in field crops a parameters is the fraction of light passing through unit leaf layer withoutinterception. Radiation profiles measured with solarimetersand photocells give values of s from 0.7 for grasses to 0.4for species with prostrate leaves. Knowing s, leaf transmissionT and leaf-area index L the light distribution in a field cropmay be described by a binomial expansion of the form {s+(I-s)T)^L.To calculate crop photosynthesis at given light intensity thisexpansion is combined with two parameters describing the shapeof the light-response curve of single leaves. Finally, the assumptionthat solar radiation varies sinusoidally allows daily totalphotosynthesis to be estimated from daylength and insolation. The theory predicts about the same potential photosynthesisin a cloudy temperte climate with long days as in a more sunnyequatorial climate with short days. When L < 3 photosynthesisincreases as s decreases, i.e. as leaves become more prostrate;but when L > 5, photosynthesis increases as s increases,i. e. as leaves become more erect. Assuming that respirationis proportional to leaf area, estimated dry-matter productionagrees well with field measurements on sugar-beet, sugar-cane,kale, and subterranean clover. Estimates of maximum gross photosynthesis(for sugar-cane and maize) range from 60 to 9 g m^–2 day^–1depending on insolation.     

Response of Insect Relative Growth Rate to Temperature and Host-Plant Phenology: Estimation and Validation from Field Data

Between 1975 to 2011, aphid Relative Growth Rates (RGR) were modelled as a function of mean outdoor temperature and host plant phenology. The model was applied to the grain aphid Sitobion avenae using data on aphid counts in winter wheat at two different climate regions in France (oceanic climate, Rennes (western France); continental climate, Paris). Mean observed aphid RGR was higher in Paris compared to the Rennes region. RGR increased with mean temperature, which is explained by aphid reproduction, growth and development being dependent on ambient temperature. From the stem extension to the heading stage in wheat, there was either a plateau in RGR values (Rennes) or an increase with a maximum at heading (Paris) due to high intrinsic rates of increase in aphids and also to aphid immigration. From the wheat flowering to the ripening stage, RGR decreased in both regions due to the low intrinsic rate of increase in aphids and high emigration rate linked to reduced nutrient quality in maturing wheat. The model validation process showed that the fitted models have more predictive power in the Paris region than in the Rennes region.     

Effects of Ultraviolet Radiation on Amphibians: Field Experiments

SYNOPSIS. Numerous reports suggest that populations of amphibiansfrom a wide variety of locations are experiencing populationdeclines and/or range reductions. In some cases, unusually highegg mortality has been reported. Field experiments have beenused with increasing frequency to investigate ultraviolet radiationas one of the potential factors contributing to these declines.Results from field experiments illustrate that hatching successof eggs is hampered by ultraviolet radiation in a number ofspecies, while other species appear to be unaffected. Continuedmortality in early life-history stages may ultimately contributeto a population decline. Although UV-B radiation may not contributeto the population declines of all species, it may play a rolein the population decline of some species, especially thosethat lay eggs in open shallow water subjected to solar radiationand in those that have a poor ability to repair UV-induced DNAdamage.     

Effects of Deltamethrin on Field Grown Potato Plants:Biochemical and Ultrastructural Aspects

The effects of repeated spraying of field grown plants of Solanumtuberosum L. with deltamethrin 24, 41 and 55 d after emergence,on chlorophyll level, oxygen uptake, RuBisCo activity and leafultrastructure, were studied. Chlorophyll amount increased in treated plants after the secondand third spraying, whereas RuBisCo activity showed a highervalue than in the controls only after the last treatment. Incontrast, the respiratory activity was stimulated by the firstspraying and no significant differences were found with theensuing treatments. The general ultrastructure of mesophyllcells was not altered by deltamethrin, but morphometric analysisof electron micrographs showed that the fractional volume ofchloroplasts and starch in the treated leaves were consistentlylower than in controls. The biochemical and ultrastructural data suggested that thevegetative cycle of the sprayed plants had been extended.Copyright1993, 1999 Academic Press Solanum tuberosum L., potato plant, deltamethrin     

Biological Control of Crown Gall: Field Measurements and Glasshouse Experiments

S ummary : An ecological study showed that the pathogeniec form of Agrobacterium radiobacter (A.r. var. tumefaciens ), biotype 2 was present in soil near galled almond seedlings, where it formed a significant proportion of the total biotype 2 population; the pathogen was not detected near healthy plants. One nonpathogenic biotype 2 isolate was able, when present in numbers approximately equal to the pathogen, to prevent crown gall induction in tomato and peach seedlings. This isolate gave complete biological control of crown gall in a glasshouse test. Six other nonpathogenic isolates did not significantly inhibit gall induction by equal numbers of the pathogen. In the field, gall induction probably depends on the size of the population of the pathogen (both absolutely and relative to that of the nonpathogen) at a wound site and on the inhibitory efficiency of the nonpathogen.     

Interrelationship Between Plant Developmental Stage, Plant Growth Rate, Nitrate Utilization and Nitrogen Fixation in Hydroponically Grown Soybean

The growth rate of the indeterminate soybean plant [Glycinemax (L.)Merr.] slows as it proceeds from vegetative phase intoreproductive growth. Yet, the well-nodulated plant acquiresmost of its nitrogen during reproductive growth. Thus, the interrelationshipbetween plant developmental stage and nitrogen fixation wasexamined. It is shown that, regardless of the age of the hydroponicallygrown soybean plant at the time of its inoculation with Bradyrhizobiumjaponicum, the highest rate of nitrogen fixation occurs duringthe pod-filling stage (R5). Nevertheless, maximum total nitrogenfixation is generally achieved when inoculation occurs at thefull-bloom stage (R2). It is shown, however, that flower budsand flowering are not responsible for the enhanced nodulationand nitrogen fixation. Rather, the data suggest that the onsetof rapid nodulation occurs soon after the initiation of thedevelopmentally programmed drop in foliar nitrate reductaseactivity. The ensuing increase in nitrogen fixation providesthe plant with much of its needed nitrogen and hence stimulatesplant mass accumulation during pod-fill. It is suggested thatnitrogen fixation enhances growth of the soybean plant by increasingits net photosynthetic efficiency during reproductive growthand by providing the needed nitrogen at the appropriate timefor maximum seed growth. Key words: Glycine max, nitrate, nitrogen fixation, nodulation     

Relationship Between N:P Ratio and Growth Rate During the Life Cycle of Calanoid Copepods: An in situ Measurement

The mean nitrogen and phosphorus contents of the calanoid copepodMixodiaptomus laciniatus Lilljeborg were measured to the stagelevel throughout the ice-free period of a high mountain lake.Our results indicate large intraspecific variations in calanoidelemental composition. While mean N as dry weight increasedfrom 3.0 ± 1.3 in nauplii to 6.0 ± 2.1 in copepodites,mean P content showed the opposite trend, varying intraspecificallyfrom 0.98 ± 0.26% in nauplii, to 0.87 ± 0.21%in copepodites and 0.51 ± 0.16% in adults. Thus, themean N:P ratio increased ontogenetically from 3.3 in naupliito 13.3 in copepodites and 24.6 in adults. Two ontogenetic parameters,the growth rate and body size, were associated with zooplanktonstoichiometry. Among all 11 copepod stages, growth rate waspositively related to %P and negatively related to %N and N:Pratio. A two-part analysis of these relationships, before andafter metamorphosis, showed that the nauplii growth rate explainednearly all the variance in naupliar P content. A high P contentin nauplii may reflect a high content of RNA, translating intorapid growth rates. Overall, these results tend to support thehypothesis linking specific growth rate with P content for copepods,but these results also suggest that the validity of this hypothesisis robustness when differences in the life history of copepodsas a consequence of metamorphosis are accounted for. We suggestthat the intra-stage variation in P content is associated withpeaks of intensive metabolic activity during the process ofmolting in copepods, and we emphasize the importance of newempirical evidence to examine this hypothesis further.     

转基因作物田间试验的频次分析

通过对加拿大转基因作物田间试验数据库19年数据的统计分析,揭示转基因作物研究的特点与发展趋势.采用EXCEL"数据透视表与数据透视图"功能进行数据分析.分析结果表明,至2006年8月止,加拿大转基因作物田间试验累计达6 927次,涉及31种作物,20多种性状和40多家公司或研究机构.1988～1998年间,试验次数呈指数方式上升,其后呈乘幂方式下降.2006年试验物种数由最高峰时期的22个降到12个,其中油菜的田间试验次数占81%.80%以上的转基因作物田间试验由孟山都和拜耳等7～8家私人公司完成.转基因田间试验的频次分布反映了转基因技术应用和发展的自身规律,是利益与风险博弈的结果.结论是只有经济价值高、风险小、消费者容易接受的转基因产品才有广阔的产业化前景.建议我国加强转基因技术在非粮食作物的应用,重视引进消化和加强转基因作物安全生产体系的建设,促进转基因技术的产业化应用.     

Integrated Control of Nitrate Uptake by Crop Growth Rate and Soil Nitrate Availability under Field Conditions

There is still disagreement about whether crop growth rate orsoil nitrate concentration control nitrogen absorption by cropsunder field conditions. The influence of these factors on thecontrol of N uptake rate was examined in the absence of waterstress, using data on dry matter production, above-ground nitrogenaccumulation and soil nitrate concentration from several N-fertilizerexperiments on winter wheat, winter oilseed rape and maize.The results confirmed that crops can accumulate nitrogen farin excess of the ‘critical dilution curve’, whichdefines the minimum amount of nitrogen needed for maximal growthrate: the N concentration in plants could exceed the criticalN concentration by 70 to 80% for the three species studied.The nitrate uptake rate index (NUI) was calculated as the ratioof actual and critical N uptake rates, at intervals of 1 week.NUI varied with nitrate concentration in the 0–30 cm soillayer according to a Michaelis–Menten equation (with oneor two components). This response was compared with the kineticsof saturation of the nitrate uptake systems: the high affinitytransport system (HATS) and the low affinity transport system(LATS). As a result, it is proposed that there is a criticalN dilution curve delimiting two domains of N use by plants.This is linked to the two nitrate transport systems, with HATSworking at low nitrate concentrations, below the critical dilutioncurve, and LATS at high nitrate concentrations, above the curve.NUI provides another method for calculating the actual nitrateuptake rate, which depends on the maximal crop growth rate (withoutN deficiency) and on the external nitrate concentration. Copyright2000 Annals of Botany Company Nitrate, uptake rate, growth rate, wheat, maize, oilseed rape, soil N availability     

Growth and Virulence of Salmonella typhimurium Grown in Different Foods

Experimental data indicate that the virulence of Salmonella typhimurium grown in different foods varies. The possibility exists, therefore, that ingestion of foods containing the same number of salmonellae may not constitute a similar health hazard.     

External Potassium Supply is not Required for Root Growth in Saline Conditions: Experiments with Ricinus communis L. Grown in a Reciprocal Split-Root System

Ricinus communis L. (castor bean) plants were grown in the absence(control) and in the presence of 100molm^–3NaCl with areciprocal split-root system, in which K⁺ was supplied to oneand NO₃^– to the other part of the root system. In theseplants shoot and, to a lesser extent, total root growth wereinhibited compared to plants with non-split roots. Without andwith NaCl, growth of roots receiving NO₃^– but noK⁺ (‘minusK/plus N-roots’) was substantially more vigorous thanunder the reverse conditions (‘plus K/minus N-roots¹).100mol m^–3 NaCl inhibited growth of minus K/plus N-roots¹to the same extent as that of non-split roots, indicating thatexternally supplied K⁺ was not required for root growth undersaline conditions. In growth media without added K⁺ the rootdepleted the external low K ⁺ levels resulting from chemicalsdown to a minimum value C_mln (1.0 to 1.4 mmol m^–3); inthe presence of 100 mol m^–3 NaCl, C_min, was higher (10–18mmol m^–3) and resulted from an initial net loss of K ⁺.C_min, was pH-dependent The distribution of K⁺, Na⁺ and Mg²⁺along the root was measured. In meristematic root tissues, K⁺ concentrations were scarcely affected by external K⁺ or byNaCl, where Na ⁺ concentrations were low, but somewhat elevatedat low external K+ and/or high NaCl. In differentiated, vacuolatedtissues K ⁺ concentrations were low and Na⁺ concentrations high,if K ⁺ was not supplied externally and/or NaCl was present.The longitudinal distribution of ions within the root was usedto estimate cytoplasmic and vacuolar ion concentrations. Thesedata showed a narrow homoeostasis of cytoplasmic K+ concentrations(100–140 mol m^–3) independent of external K ⁺ supplyeven in the presence of 100 mol m ^–3 NaCl. CytoplasmicNa ⁺ concentrations were maintained at remarkably low levels.Hence, external K⁺ concentrations above C_min, were not requiredfor maintaining K/Na selectivity, i.e. for controlling Na⁺ entry.The results are discussed with regard to mechanisms of K/Naselectivity and to the importance of phloem import of K⁺ forsalt tolerance of roots and for cytoplasmic K⁺ homoeostasis. Key words: Ricinus communis, nitrate, potassium, root (split-root), salt tolerance, phloem transport     

油菜素甾醇类化合物调控园艺作物生长的研究进展

油菜素甾醇类化合物是一类对植物的生长发育具有重要影响的新型植物激素。本文综述了油菜素甾醇类化合物在园艺作物地上部、根系、花和果实的生长中,以及器官离体培养和快速繁殖中的主要生理功能及分子机制。     

Rate of Contaminant Bioavailability in Artificial Soil-Water Column Experiments

Bioavailability of organic contaminants is a key parameter in estimating the fate and transport of contaminants in the environment. Its quantification is necessary for assessing the bioremediation potential of a contaminated site or for evaluating the hazard associated with the presence of the contaminant. However, there is a lack of methods that quantify biovailability under flow-through conditions. Therefore, a method was developed based on mass-balance analysis of contaminant breakthrough curves to quantify a bioavailability rate. The method was performed on an eight-column study where pentachlorophenol (PCP) was injected through saturated columns packed with a blend of sterile or inoculated sand and PCP-sorbing resin. Columns varied in sorption capacity, pore-water velocity and biodegradation activity. Breakthrough curves were modeled using a classic approach that includes advection-dispersion, equilibrium and first-order sorption, as well as biodegradation. Results showed that the bioavailability rates (non-dimensional numbers ranging from 0.02 for a sorptive column to 0.32 for a non-sorptive one) were directly related to the limiting kinetic mechanism. It was also demonstrated that the contaminant aqueous phase concentration does not adequately represent its bioavailability under flow-through conditions.