The Dielectric Relaxation of Water in Plant Tissue

Thermally stimulated depolarization current (TSDC) measurementson plant leaves and stems of six different species in the temperaturerange of 77–300 K revealed the existence of three differentdispersions. The first dispersion at low temperatures, whichis attributed to the relaxation of loosely bound water moleculeswas studied in detail in an attempt to obtain information onthe possible structures of water in plant tissue. Its characteristicsdiffer for various plant tissues, indicating a different organizationof water in those plant tissues. The dispersion can be describedby a continuous distribution of relaxation times t with boththe activation energy W and the pre-exponential factor To inthe Arrhenius equation being distributed parameters. The spectrumof W and T_o was determined for E. globulus and O. europaea leafsamples. The mean values of T and W are larger and that of T_osmaller than the corresponding values for free (bulk) water.The results favour a model of the organization of water in clustersrather than in multilayers and indicate a stronger binding ofwater in living systems. Key words: Dielectric relaxation, distribution of relaxation times, free and bound water     

Dielectric Study of the Physical State of Electrolytes and Water Within Bacillus cereus Spores

Dielectric measurements revealed that dormant spores of Bacillus cereus have extremely low conductivities at high frequencies (50 MHz) and so must contain remarkably low concentrations of mobile ions both within the core and in the surrounding integuments. Activation, germination, and outgrowth were all accompanied by increases in conductivity of the cells and their suspending medium, and this result indicated that intracellular electrolytes had become ionized and leaked from the spores. High-frequency dielectric constants of spores were consistent with normal states for cell water. These values increased during successive stages of development from dormant spore to vegetative bacillus, and they could be directly related to increases in cell water content. In all, the results refuted a model of the dormant spore involving freely mobile, ionized electrolytes and supported a model involving electrostatically bound electrolytes.     

On the Strength of Herbaceous Vascular Plant Stems

During the past 120 years researchers have tried to providean understanding of the relationship between the arrangementof stiffening tissue in the cross-section of plant stems andtheir mechanical integrity. The mechanical analysis of verticalstems of self-supporting plants has traditionally been concernedwith issues involving global and local stability of the stem,and with stresses developed due to wind loads. Plant stem tissue,considered as a material, is both heterogeneous and highly anisotropic,and this must be reflected in any characterization of its mechanicalbehaviour. This fact strongly influences the type of failurecriterion which should be applied for compressive failure ofthe stem subjected to loads causing bending. It is shown, here,that applying modern ideas as to the appropriate criteria forcompressive failure of fibre-reinforced composite materialscan influence how we assess the efficacy of various stelar arrangementsconcerning their ability to fulfill their mechanical function.Specifically, it is demonstrated that peripheral arrangementsof supporting tissue are, in some circumstances, less advantageousthan more uniform distributions of this tissue. Plant stems; stem bending; compressive strength; stelar types     

A Proton Spin-Echo Study of the State of Water in Frog Nerves

A proton spin-echo study of the water in the sciatic nerve trunk of the bullfrog reveals two distinct types of water as distinguished by their spin-spin relaxation times. The relative concentrations of these two types were determined for nerves which had been treated with normal Ringer's solution and also for nerves which had been treated with potassium-doped (0.15 M) Ringer's solution. In both cases the relative concentrations are the same as those previously determined through signal integration of high resolution proton magnetic resonance spectra obtained for the same systems, although the high resolution studies were performed on nerves doped with paramagnetic ions and the spin-echo studies were performed on undoped nerves. The doping procedure would appear to be a valid and very useful way of studying water in this neural system.     

Plant Height and the Properties of Some Herbaceous Stems

The volume fraction (VF) of lignified tissues and density-specificstiffness (the quotient of the Young's elastic modulus E andbulk tissue-density     

Regeneration of Tissues in Wounded Stems: A Quantitative Study

When a dicotyledonous stem is wounded by longitudinally splittinga young internode into halves, cells near the cut surface proliferateto form a callus within which vascular tissues differentiateand tend to restore a vascular cylinder in each half. Threephases of regeneration after wounding were identified and quantifiedin stems of three Solanaceous species. (1) In an initial ‘lag’phase, lasting about 2 d, neither cell division nor enlargementwere detected, but mitotic figures were observed within about300 µm of the cut surface. (2) Throughout a second, ‘division’phase, from about days 2–10, cell division and enlargementoccurred. Both were initiated mainly in the two cell layersnearest the surface. A mass of callus formed, with new cellwalls mostly parallel to the surface. Cell enlargement laggedbehind cell division for the first few days, so that mean radialcell diameter decreased until day 6, thereafter remaining almostconstant at 30–40 µm. Towards the end of this phase,mitoses ceased within the callus except in the positions ofthe future vascular and cork cambia, where radial cell diameterfell towards a constant 15–20 µm. (3) During a third,‘differentiation’ phase, cell division was restrictedto the cambial zones, and derivatives differentiated into cork,phloem or xylem according to position. The rate of increasein cell number per transect was 1.5–2.0 cells d^–1,of which more than half was xylem. Capsicum annuum L., sweet pepper, Lycopersicon esculentum Mill., tomato, cambium, cell division, differentiation, regeneration, wounding of stems, xylem     

A Study on the Constituents of Stems and Leaves of Astragalus membranaceus

A new saponin was isolated from stems and leaves of Astragalus membranaceus Bunge. On the basis of chemical reaction and spectroscopic (MS, NMR)analysis, it is identified as cycloastragenol 3-O-β-D-glucoside.     

Study of Bound Water of Poly-Adenine Using High Frequency Dielectric Measurements

The high frequency dielectric constant of poly-adenine (poly-A) was measured between 1 MHz and 1 GHz. The purpose of these experiments was to investigate the state of water molecules that are bound to the charged groups of the poly-A molecule. Analysis of the data using the Maxwell's mixture equation revealed the dielectric constant of bound water higher than we expected. Using Onsager's internal field in Debye's equation, we calculated the dielectric constant of water in the vicinity of a charged ion. The result of this computation demonstrates that the dielectric constant of bound water is much smaller than the normal value only in the immediate proximity of charged ions (within 2 Å). The dielectric constant increases rapidly to the normal value as the distance increases from 2 to 4 Å. This observation indicates that charged sites of polyions have only short range interactions with the surrounding water molecules. However, this conclusion pertains only to rotary diffusion of bound water since dielectric measurement is unable to detect translational diffusion.     

东北刺人参茎次生木质部结构植物学研究

东北刺人参为五加科植物,本文对其茎次生木质部进行结构植物学研究,发现其为环孔材,射线为异形Ⅱ型。在离析材料中,发现其导管分子穿孔板有单穿孔板和梯状穿孔板2种。具不同穿孔板的导管分子可分为8种。还有维管管胞、纤维管胞和韧型木纤维。8种导管分子是只有中央具1个单穿孔的导管;中央有2个穿孔的导管,其中一个孔是单穿孔,另一个是梯状穿孔;一端是梯状穿孔板,另一端为孔纹增厚的导管;一端是单穿孔。另一端是孔纹增厚的导管;一端为单穿孔板。另一端为梯状穿孔板的导管;两端都是梯状穿孔板的导管;侧壁具有3个穿孔的导管;两端都具单穿孔的导管。在东北刺人参的个体发育中重演了系统发育过程中导管分子穿孔板的演化过程。     

植物光合机构的状态转换

植物光合机构的状态转换是一种通过光系统Ⅱ的捕光天线色素蛋白复合体（LHCⅡ）的可逆磷酸化调节激发能在两个光系统间的分配来适应环境中光质等短期变化的机制．一般植物光合机构的LHCⅡ磷酸化主要受电子递体质醌和细胞色素b6f复合体氧化还原状态的调节,从而影响其在两种光系统间的移动。植物光合机构的状态转换也可以通过两种光系统相互接近导致激发能满溢来平衡两个光系统的激发能分配。外界离子浓度骤变可以引起盐藻LHCⅡ磷酸化,其调节过程与电子递体的氧化还原状态无关。绿藻的状态转换可以调节细胞内的ATP供求关系。     

Significance of the Occurrence of Time Lags in the Transmission of Hydraulic Shock Waves through Plant Stems

Hydraulic shock waves were introduced into plants by pruning.These shock waves were monitored by a sap flux meter attachedto the plant at some distance from the excision. The measuredshock waves occurred a short time after pruning. An electricalanalogy is proposed to explain the time lags. The analogy suggestedthat, in plants undergoing auto-oscillatory behaviour, thereshould be a time lag in the transmission of oscillations insap flux along a stem. A plant undergoing auto-oscillatory watermetabolism showed a time lag of this type.     

Computer Simulation of the Dielectric Properties of Liquid Water

Abstract

Monte Carlo simulations of water in the NVT ensemble using three models (SPC, TIP4P and TIPS2) are reported. The internal energy, dielectric constant, and the site-site radial distribution functions of liquid water (temperature 300 K and mass density 1 gm cc^?1) were calculated and compared with experiment. It was found that of the three intermolecular potential models, SPC gives the best dielectric constant. Since SPC also yields acceptable results for the energy and structure, it is judged to be the best among the three models studied.     

On-line Estimation of the Rate of Sap Flow in Plant Stems Using Stationary Thermal Response Data

The heat pulse method for the measurement of the rate of sapflow in plants suffers from two drawbacks, viz. the discontinuousnature of the measurements and the lack of a precise mathematicalformulation of the heat fluxes. To overcome these drawbacksa random noise heat signal has been used as an input and twosensor pairs have been used for the measurement. A model isgiven that employs the signal from one sensor pair as inputand the signal from the second pair as output of a heat transportsystem. Thus the adverse effects of radial heat conduction havebeen eliminated. Simulation models with the rate of sap flowas one of the parameters have been fitted to the stationaryresponse data with an on-line parameter optimization algorithm.The method has been validated in applications to artificialdata and to real data obtained from a plastic tube and fromtomato plants. Key words: Sap flow, Heat pulse method, Continuous measurement     

The State of Water in Polarized and Depolarized Frog Nerves: A Proton Magnetic Resonance Study

The high resolution proton magnetic resonance spectrum of the sciatic nerve of the frog was studied in both the polarized and depolarized states. Paramagnetic salts were introduced into the system in order to separate the signals from the intra- and extracellular environments. It was determined that about 65% of the proton signal from the nerve trunk was accounted for by the intracellular environment in the polarized nerve trunk and that this percentage decreased to about 34% in the depolarized case.

The temperature dependence of the line widths of the intracellular proton signal was studied. The enthalpy and entropy of activation for proton exchange between the intra- and extracellular environments were found to be 11.1 kcal/mole and -17.1 cal/deg-mole respectively. The pseudo-first-order rate constant for proton exchange between the intra- and extracellular environments was determined at 20°C and shown to agree with the measured permeability coefficients of similar cells.

Data are presented which indicate that the pseudo-first order rate constant for proton exchange between the two environments decreases upon depolarization of the nerve trunk and that the proton spin-spin relaxation time of the protons of intracellular water decreases significantly with depolarization.

These results indicate a possibly quite important role of water in neural phenomena.

     

Estimating Water Flux through Stems of Scots Pine with Tritiated Water and Phosphorus-32

The radioisotopes of tritium (³H) and phosphorus-32 (³²P) weresimultaneously injected into the conducting tissue of more than40 Scots pine trees over a 6 month period. Analysis of coresamples indicated that ³²P and ³H are transported by mass movementat similar rates. ³H exhibits diffusion as well as mass flowproperties. The strong beta emission of ³²P at the bark surfacewas monitored to determine the velocity of the pulse. Core samplesprovided an estimate of the volume of waterfilled conductingtissue. The calculations of flux were compared with actual uptakeby two trees severed at their bases and supported in water-filledcontainers. Over a 5 d period, periodic estimations of cumulativewater uptake showed an excellent linear relationship with measureduptake (r² 0.98). Refinements in the model are discussed, emphasizingthe importance of assessing diurnal variation in sapwood watercontent.     

An Investigation of the Bound Water in Tendon by Dielectric Measurement

The dielectric constant of natural tendon in the frequency range of 200 Hz to 100 kHz has been determined as a function of temperature (300-450°K) for water concentrations ranging from about 6 to 16% by weight. The results compare well with the approach taken by Haggis and his coworkers. Based on the assumption that at low concentration of water the probability of water-water bonding is small and hence may be disregarded, a structure for water in the collagen matrix is proposed in which the water is either bonded in one of four possible states to the polar groups of the polypeptide chains, or is unbound. In determining the distribution of the water among these states an approach similar to that of Haggis and his co-workers, in conjunction with the order-disorder theory of Bragg and Williams, is used. The number of water molecules per unit volume is then determined experimentally by relating it to weight loss as a function of temperature, as determined by thermogravimetric analysis. The dispersion which is normally found in dipolar substances has not been found for tendon. A maximum in the value of the dielectric constant is observed to occur between 25 and 80°C, the temperature depending upon the heating rate.     

植物根系吸水过程中根系水流阻力的变化特征

以植物根系吸水的人工模拟试验所测得的数据为依据,运用水流的电模拟原理,定理分析了不同土壤水分水平处理下植物根系吸水过程中根系水流阻力各主要分量的大小、变化规律及其相对重要性．结果表明,在同一水分水平处理中,植物根内木质部传导阻力（Ｒｃ）随生长时间的推移而减小,随土层深度的加深而增大,土根接触阻力（Ｒｓｒ）、植物根系吸收阻力（Ｒｒ）随生长时间表现出先下降后上升阶段的动态变化特征;在不同水分水平处理中,Ｒｃ、Ｒｓｒ、Ｒｒ均随土壤湿度减小而大幅度增大;在植物根系水流阻力各分量中,Ｒｒ占根系水流阻力的比例为５５％～９６％,Ｒｓｒ约占根系水流阻力的４％～４５％,而Ｒｃ仅占根系水流阻力的７×１０－６,故Ｒｒ是决定植物根系吸水速率的重要因素     

A New Dendrometer for the Measurement of Small Stems in the Laboratory

A new highly sensitivo dondrometor designed principally foruse in the laboratory or in growth rooms is described. The apparatuscaused minimal disturbance to, and distortion of, the stem beingmeasured. Typical readings obtained with the apparatus are showntogether with measurements of sap flux, made with an improvedmagnetohydrodynamic sap flux moter.