A Model of Plant Hydraulics Under Non-equilibrium Conditions: I. STEMS

Oscillations in sap flux in two branches of a plant were foundto be non-synchronous but frequently phase-locked, even thoughthe branches had very different energy budgets. Time lags inthe transmission of oscillations along a stem were measured,and analysed in terms of an electrical transmission-line analogy.The equivalent ‘circuit elements’ in the stem wereidentified and their values calculated. These values were usedto derive the expected time lags of oscillations along a stem.Derived values agreed closely with those measured.     

A Dynamic Model for Plant Growth: Validation Study Under Changing Temperatures

A dynamic simulation model to describe vegetative growth ofplants, for which some functions and parameter values have beenestimated previously by optimization search techniques and numericalexperimentation based on data from constant temperature experiments,is validated under conditions of changing temperatures. To testthe predictive capacity of the model, dry matter accumulationin the leaves, stems, and roots of tobacco plants (Nicotianatabacum L.) was measured at 2- or 3-day intervals during a 5-weekperiod when temperatures in controlled-environment rooms wereprogrammed for changes at weekly and daily intervals and inascending or descending sequences within a range of 14 to 34°C. Simulations of dry matter accumulation and distributionwere carried out using the programmed changes for experimentaltemperatures and compared with the measured values. The agreementbetween measured and predicted values was close and indicatesthat the temperature-dependent functional forms derived fromconstant-temperature experiments are adequate for modellingplant growth responses to conditions of changing temperatureswith switching intervals as short as 1 day. Nicotiana tabacum, tobacco, translocation, partitioning, root growth, shoot growth     

Modelling Plant Growth Under Varying Environment Conditions in a Uniform Canopy

A model for the growth of plants is proposed. It extends theconcept of thermal time to include the effects of photosyntheticallyactive radiation and carbon dioxide concentration in a formulathat is analogous to the rate of flow through a set of conductancesin series. The formula transforms time periods of differingor varying environmental conditions to a consistent plant-relatedbasis. The integrated plant environmental time is used in theexpolinear equation of Gourdriaan and Monteith (1990) to providea simple dynamic model for the growth of mutually shading plantsin a uniform canopy of an even-aged monoculture. The model is fitted to data from lettuce and cauliflower. Eachhad been grown, in a glasshouse, at four different times ofyear and at four densities. The plant environmental time relationallows for the different conditions of temperatures and light,and the expolinear equation then predicts the set of growthcurves at the different densities. Parameters values differbetween the species, as would the predicted values of environmentaltime. An improved fit is obtained by using the mutual shading relationto modify the radiation term only, rather than the whole environmentalgrowth rate expression. Most of the observed results differby less than one day in time from the fitted values. Corroborationfor the model is provided by values of an effective leaf arearatio, estimated from the effects of plant density and plantweight upon competition for radiation.Copyright 1993, 1999 AcademicPress Growth, model, temperature, PAR, carbon dioxide, plant environmental time, density, expolinear, monocrop, competition, lettuce, cauliflower     

Thermotolerance of Photosystem 2 of Three Alpine Plant Species Under Field Conditions

The species specific response of photosystem 2 (PS2) efficiency and its thermotolerance to diurnal and seasonal alterations in leaf temperature, irradiance, and water relations were investigated under alpine field conditions (1 950 m) and in response to an in situ long-term heat treatment (+3 K). Three plant species were compared using the naturally occurring microstratification of alpine environments, i.e. under contrasting leaf temperatures but under similar macroclimatic conditions. Thermotolerance of PS2 showed a high variability in all three species of up to 9.6 K. Diumal changes (increases or even decreases) in PS2 thermotolerance occurred frequently with a maximum increase of +4.8 K in Loiseleuria procumbens. Increasing leaf temperatures and photosynthetic photon flux density influenced thermotolerance adjustments. Under long-term heating (+3 K) of L. procumbens canopies with infra-red lamps, the maxima of the critical (T_c) and the lethal (T_p) temperature of PS2 increased by at least 1 K. Thermotolerance of the leaf tissue (LT₅₀) increased significantly by +0.6 K. The effects of slight water stress on thermotolerance of PS2 were species specific. High temperature thresholds for photoinhibition were significantly different between species and increased by 9 K from the species in the coldest microhabitat to the species in the warmest. Experimental heating of L. procumbens canopies by +3 K caused a significant (p>0.01) upward shift of the high temperature threshold for photoinhibition by +3 K. Each species appeared to be very well adapted to the thermal conditions of its microhabitat as under the most frequently experienced daytime leaf temperatures no photoinhibition occurred. The observed fine scale thermal adjustment of PS2 in response to increased leaf temperatures shows the potential to optimise photosynthesis under varying environmental conditions as long as the upper thermal limits are not exceeded.     

Oscillatory Transpiration in a Cotton Plant: II. A MODEL

A generalized conceptual model of oscillatory transpirationin a cotton plant growing in a nutrient solution under constantenvironmental conditions is presented. The model is based uponthe results and observations of an experimental study and thecontemporary literature. It incorporates the values of parameters,of initial and boundary conditions, and of significant variablesin the transpiration stream. A non-linear coupling consistingof a hysteresis loop with a time-variant constraint acting betweenthe guard cell potential and stomatal resistance is proposed.Mathematical equations based upon the network variables weresolved via a simulation language (CSMP—IBM/360). The modelshowed gradually damped oscillations early in the light periodand sustained oscillations later in the light period. The resultingsimulation output agrees satisfactorily with pattern of oscillationsobserved in vivo. Root resistance changes through the day causedminimal effect on oscillation. The principal causal effect foroscillatory behaviour appeared to be due to stomatal effects.     

Development of Dry Skin in the NOA Mouse Under Individual Housing Conditions: A Potentially Useful Animal Model for Evaluating Moisturizing Effects.

In a previous study, we reported the development of grossly observable dry skin in all of the Naruto Research Institute Otsuka Atrichia (NOA) mice that were housed individually. In the present study, dermal physiological function tests were conducted and the usefulness of this dry skin model for evaluating the efficacy of topical moisturizers was assessed. As a result, we have confirmed a marked reduction in the water content of the stratum corneum in these animals. Therefore, the development of dry skin in the NOA mouse strain under individual housing conditions may be expected to serve as a useful animal model for evaluating topical moisturizers. Specifically, the water content of the stratum corneum was restored in proportion to the oil content of the ointment base used to treat the animals, and the moisturizing effects of urea were confirmed in animals treated with urea-containing ointment. In addition, when the animals that had been housed individually were returned to group housing conditions, the water content of the stratum corneum was restored, with a corresponding improvement in dry skin. This finding suggests that socio-psychological factors are involved in the etiology of dry skin in individually housed NOA mice.     

Plant Growth and Photosynthetic Characteristics of Soybean Seedlings Under Different LED Lighting Quality Conditions

Journal of Plant Growth Regulation - Light-emitting diodes (LEDs) have recently been widely used as light sources for the cultivation of plants in controlled environments. However, before LEDs can...     

Biophysical Characterization and Folding Studies of Plant Protease,Wrightin: Identification of Folding Intermediate Under Different Conditions

Wrightin, a serine protease from Wrightia tinctoria, has been used as model system to examine structure-function and stability. Our studies show high stability of the enzyme with major elements of secondary structure being β-sheets. Under neutral conditions the enzyme is stable in 8 M urea and high temperature. GuHCl induced unfolding of wrightin at lower pH cannot be satisfactorily fit to a two state model for unfolding. Multiple intermediates were identified during unfolding of wrightin. Further, two intermediates, early and late are identified in the urea induced unfolding pathway at pH 3.0. Spectroscopic properties of intermediate states are analyzed and interpreted.     

新型禾本科模式植物——二穗短柄草

文章介绍二穗短柄草这一种新型的禾本科模式植物的分类地位、生物学特性和基因组学等方面的研究进展.     

The Translocation of Sulphonamides in Higher Plants: II. ENTRY INTO THE LEAVES OF WHEAT

Uptake of a number of suiphonarnides and p-aminobenzoic andsuiphanilic acids can be represented by equations derived fromPick's Law of diffusion. The diffusion constants so derivedhave a Q¹⁰ of the order of 1.4 or 1.7, indicating that the processis primarily physical. The Fick's Law equations provide a measureof the permeability of the system and of the size of the effectivevolume into which the compound is diffusing. Assuming that thebasic process is diffusion from water outside the tissue intowater inside the tissue, the size of the effective volume isconditioned by the absorption of the compound from the aqueousphase of the free space. With sulphanilaniide the effectivevolume is finite while with p-amino benzoic acid the effectivevolume is infinite within the limits of the experiment and concentrationsup to three times that of the treating solution may be attained.A proportion of the suiphanilamide will diffuse out of shootsimmersed in water but p-aminobenzoic acid is held irreversiblyby the tissue.     

Copper Nanoparticle Application Enhances Plant Growth and Grain Yield in Maize Under Drought Stress Conditions

Journal of Plant Growth Regulation - Abiotic stresses, including drought, detrimentally affect the growth and productivity of many economically important crop plants, leading to significant yield...     

螺旋藻连续培养与动力学模型

在内循环气升式光生物反应器中 ,研究了钝顶螺旋藻 (SpirulinaplatensisGeitler)细胞的连续生长及其对碳源底物的利用特性。结果表明 :随着稀释率的增大 ,反应器中碳源浓度和细胞浓度分别呈上升和下降趋势 ,它们之间的关系可用Monod类型的方程很好地加以关联。细胞产率和碳消耗速率与稀释率的关系存在峰值现象 :在本实验条件下 ,最大细胞产率为 0 .36 2g/(L·d) ,最大碳消耗速率为 0 .177g/(L·d) ,此时稀释率为 0 .45 /d ,细胞浓度为OD560 =1.2 82 ,细胞对碳的得率系数为 2 .0 5 0g/g。所提出的连续培养动力学模型与实验数据拟合较好     

The Circadian Rhythm of Leaf Movement of Coleus blumei x C. frederici, a Short Day Plant. I. Under Constant Light Conditions

A new instrument for the recording of leaf movement rhythm is described. Coleus blumei x C. frederici, a short day plant, exhibits a circadian rhythm of leaf movement. The period length of the free running rhythm is shortest in continuous darkness and is increased with an increase in the light intensity. The amplitude of the rhythm tends to damp in continuous bright light.