A Study of the Growth of Four Provenances of Pinus contorta Dougl

A study was carried out on the growth of third- and fourth-yearseedlings of four provenances of Pinus contorta, two of whichwere from high elevations and two from coastal sites. Markeddifferences in height growth were observed, the two coastalprovenances showing significantly greater growth than the twomontane ones. These growth differences were due to differencesin the numbers of needle and stem ‘internode’ primordialaid down in the resting buds in the preceding year, and notto differences in ‘internode’ length in the annualextension shoots. The differences in height growth were paralleledby differences in dry weight. A greater relative height growthrate was shown by one coastal provenance and probably also bythe second, than by the montane provenances. The levels of reservematerials were similar in all provenances. These results arediscussed and it is concluded that the growth of montane provenancesmay be ‘sink limited’ rather than ‘sourcelimited’ when they are grown at lower altitudes.     

Pyrimidine Nucleotide Biosynthesis in Vinca rosea Cells: Changes in the Activity of the de novo and Salvage Pathways during Growth in a Suspension Culture

Marked changes in the activity of the ‘de novo’and ‘salvage’ pathways of pyrimidine biosynthesisduring growth of Vinca rosea cells in a batch suspension culturewere observed. The activity of these pathways was investigated by determiningthe contribution of ¹⁴C of [2-¹⁴Cluracil, 12-¹⁴Cluridine. and[6-¹⁴Clorotate to the cell constituents and by measuring theactivity of the several enzymes of these pathways. During the lag phase of the culture, ‘uracil-’ and‘uridine-salvage’ pathways made the predominantcontribution to nucleotide biosynthesis, but, following theinitiation of cell division, the ‘de novo’ pathwayfor nucleotide biosynthesis operated appreciably. These results suggest that nucleotide synthesis during cellgrowth in a suspension culture can be divided into two stages:a ‘turnover stage’, during the lag phase of cellgrowth, and a ‘true biosynthetic stage’, which isinitiated in the cell division phase.     

Effect of large- and of small-bodied zooplankton on phytoplankton in a eutrophic oxbow

Macrozooplankton and microzooplankton effects on the phytoplanktonwere measured in situ in a eutrophic lake. Indigenous phytoplanktonwere incubated for 5 days in 301 mesocosms with either the macro-and microzooplankton (complete), microzooplankton only (micro)or no zooplankton (none). Changes in phytoplankton biovolumewere investigated. Rotifer densities became significantly higherin the ‘micro’ treatment than in the ‘complete’and ‘none’ treatments. Total algal biovolume changedlittle in the ‘complete’ and ‘none’treatments, but increased significantly in the ‘micro’treatment. The results suggest that macrozooplankton (Daphniamagna) suppressed it and microzooplankton (Keratella cochlearis)enhanced it. They had opposite net effects on the phytoplankton.Suppression of microzooplankton by Daphnia probably had an indirectnegative effect on the phytoplankton.     

Coastal eutrophication: recent developments in definitions and implications for monitoring strategies

The word ‘eutrophication’ has its root in two Greekwords: ‘eu’ which means ‘well’ and ‘trope’which means ‘nourishment’. The modern use of theword eutrophication is related to inputs and effects of nutrientsin aquatic systems. Despite a common understanding of its causesand effects, there is no agreed definition of coastal eutrophication.This communication aims to review recent developments in thedefinitions of coastal eutrophication, all of which focus on‘accelerated growth’, and to discuss the implicationsin relation to monitoring and assessment of ecological status.It is recommended that measurements of primary production, beinga sensitive and accurate indicator of eutrophication, shouldbe mandatory when monitoring and assessing the ecological statusof coastal waters. Written responses to this article should be submitted to KevinFlynn at k.j.flynn@swansea.ac.uk within two months of publication.For further information, please see the Editorial ‘Horizons’in Journal of Plankton Research, Volume 26, Number 3, Page 257.     

Topophysis affects the Potential of Axillary Bud Growth, Fresh Biomass Accumulation and Specific Fresh Weight in Single-stem Roses (Rosa hybrida L.)

Topophysis, the effect on growth and differentiation of positionof axillary buds along the shoot, was studied by propagatingfive-leaflet-leaf single-node cuttings which were excised fromseven stem positions and grown as single stemmed plants. InRosahybrida ‘Korokis’ Kiss®, ‘Tanettahn’Manhattan Blue®, and ‘Sweet Promise’ Sonia®,following release of the buds from apical dominance by excision,morphogenetic development was studied until anthesis. The timefrom excision/planting until onset of bud growth, visible flowerbud appearance, and anthesis was generally shorter in plantsoriginating from apical bud positions than from basipetal positions.Topophysis mainly affected the onset of axillary bud growth;the earliest growth and development was found in cuttings fromthe second uppermost node position. This node tended to havethe lowest plastochron value, which indicated the existenceof a transition between sylleptic and proleptic buds. Stem lengthat visible flower bud and at anthesis generally increased asthe cutting position changed basipetally until the second lowestposition, and the number of five-leaflet-leaves at anthesisand the total number of nodes generally increased basipetally.For internode length, growth rate, and fresh biomass efficiencythe cuttings taken from the uppermost and lowermost positionsgenerally had significantly lower values than cuttings fromall medial positions. At anthesis, plants originating from cuttingsexcised from lower medial positions generally had a higher freshweight, greater flower stem diameter, and a significantly higherspecific fresh weight than those plants originating from apicalor basal positions. Among the cultivars, Sonia was the mostefficient in increasing fresh biomass and had the highest growthrate, whereas Manhattan Blue possessed the highest specificfresh weight, indicating a higher plant quality. It is suggestedthat topophysis inRosa is an independent phenomenon intrinsicto the axillary bud. apical dominance; axillary bud growth; fresh biomass accumulation; cut rose; flowering; Rosaceae; Rosa hybrida L.; rose; shoot growth; single-stem roses; specific fresh weight; topophysis; quality     

A radiochemical method for secondary production in planktonic Crustacea based on rate of chitin synthesis

A radiochemical method has been developed to measure the growthrate of aquatic Crustacea, based on the rate of incorporationof [¹⁴C]NAG, from [¹⁴C)UDP-NAG, into the chitinous exoskeleton.Daphnia was used as the test organism. The specific activity(d.p.m. nmol^–1) of the [¹⁴C]UDP-NAG precursor pool increasedlinearly with time, as did the rate of [¹⁴C]NAG incorporationinto exoskeletons. Growth rates were calculated in a manneranalogous to that used in the ¹⁴C ‘primary production’technique. Comparison of growth rates derived from the [¹⁴C]chitinsynthesis method to those obtained by independent conventionalmeans showed agreement to within 5%. This is the first radiochemicalmethod to accurately measure the growth rate in a metazoan.It can potentially be applied to field populations of any organismswhich synthesize chitin.     

Relative Sensitivity and Tolerance of some Gladiolus Cultivars to Sulphur Dioxide

Five Gladiolus cultivars, namely ‘Aldebaran’, ‘BrightEye’, ‘Illusion’, ‘Manisha’ and‘Manmohan’, were exposed to 1 and 2 µg l^–1sulphur dioxide to test their relative-sensitivity toleranceto the pollutant Plants were fumigated experimentally for 2h daily Foliar injury symptoms were observed first in ‘Manisha’followed by ‘Aldebaran’ and ‘Illusion’at the higher dose Photosynthetic pigments and leaf extractpH were significantly decreased, particularly in ‘Manisha’and ‘Illusion’ Overall disturbances in the plantmetabolism due to SO₂ treatment led to retarded growth of plants,as evident from decreased shoot length and phytomass valuesThe order of sensitivity of the five Gladiolus cultivars toSO₂ was as follows, with the greatest first Manisha, Illusion,Aldebaran, Bright Eye, Manmohan Cultivars, Gladiolus, sensitivity, sulphur dioxide, tolerance     

Source-sink Relationships, Seed Sucrose Levels and Seed Growth Rates in Soybean

Field experiments using two soybean (Glycine max L. Merrill)cultivars (‘Elgin 87’ and ‘Essex’) wereconducted for 2 years near Lexington, KY, USA to evaluate theeffect of source-sink alterations on seed carbohydrate statusand growth. Sucrose concentrations in developing cotyledonsof control plants were consistently low (<50 m M) early inseed development, but they increased to 100–150 m M byphysiological maturity. The concentrations increased in bothyears by 47 to 59% when 90% of the pods were removed from ‘Elgin87’, but the increase had no effect on individual seedgrowth rate (SGR). Shading (80%) reduced cotyledon sucrose levelsand SGR in both years. The critical cotyledon sucrose concentration(the concentration providing 80% of the maximum cotyledon growthrate) was estimated fromin vitro cotyledon growth at sucroseconcentrations of 0–200 m M. These critical concentrationsvaried from 72–124 m M;in planta control cotyledon sucroseconcentrations were below this critical level during the firsthalf of seed growth but exceeded it in the later stages of growthin all experiments. The estimated critical concentration wasconsistent with the failure of in planta SGR to respond to anincrease in assimilate supply and with the reduction in SGRassociated with a decrease in assimilate supply. The resultssuggest that soybean SGR is generally sink limited if photosynthesisincreases during seed filling, but source limited if photosynthesisis reduced. Copyright 2001 Annals of Botany Company Glycine max(L.) Merrill, soybean, source-sink ratios, sucrose, starch, depodding, shade, in vitro culture     

Homeostasis in Nitrogenous Uptake/Assimilation by the Green Alga Platymonas (Tetraselmis) striata (Prasinophyceae)

When nitrate, ammonium, or urea were the sole nitrogen sourcesfor the growth of Platymonas striata there was a short initiallag period, after which uptake/assimilation occurred at a constantrate. Glycine ‘uptake’ was however non-linear withtime. Addition of ammonium or urea markedly inhibited nitrate‘uptake’ whereas although glycine was initiallytotally inhibitory, nitrate ‘uptake’ recommencedabout 1 h after addition, but at a greatly reduced rate. Ammoniumtotally inhibited urea ‘uptake’, but did not inhibitglycine ‘uptake’. When ammonium, urea, or glycinewere present at the same time as nitrate the total rate of nitrogen'uptake/assimilation was within 40% (or closer) of that of nitratenitrogen ‘uptake’ alone. In the first two casesthis reflected a total switching off of nitrate ‘uptake’whilst the new substrate was assimilated at a rate similar tothe initial nitrate rate, whereas in the case of glycine, bothsubstrates were used simultaneously. Once the concentrationof any of the inhibitory nitrogen sources had been reduced toa low level the ‘uptake’/assimilation of nitraterecommenced. It is suggested that the ability of P. striatato maintain a more or less constant rate total nitrogen ‘uptake’/assimilationirrespective of the mixture of utilizable nitrogen sources presentedto it, is not due to controls at the level of the entry of substrateinto the cell, but to intracellular actions at the enzyme level.The relative constancy of, and high rate of ‘uptake’,irrespective of nitrogen source and over a wide range of extracellularconcentrations, is tentatively considered to be due to saturationof the assimilatory mechanisms under the conditions employed;all the sources lead, either directly or indirectly, to theproduction of amino groupings for entry into nitrogenous metabolism.This homeostasis of nitrogen ‘uptake’/assimilationwould clearly be of considerable benefit to the alga in nature,enabling it to maximize growth in changing environmental conditions. Platymonas striata, nitrogen update, nitrogen assimilation     

Simultaneous measurement of root force and elongation for seedling pea roots

A new method was developed to measure simultaneously, continuously,and non-destructively the elongation rate and the force exertedby the roots of seedlings grown in moist air. A pea (Pisum sativumL. cv. Helka) seedling was suspended inside a modified sampletube on one side of a pulley, with the tip of the radicle pushingon to a force transducer through a hole in the tube. The forceon the root tip was monitored by the force transducer and couldbe adjusted by adding or removing mass from the counterweighton the other side of the pulley. As the root grew, the sampletube was raised and the elongation of the root was monitoredusing a linear variable differential transformer (LVDT) attachedto the thread connecting the sample tube and counterweight.The changes in elongation rate were recorded which occurredin response to increases and decreases in the applied force.Forces of up to 125 mN were exerted on the root, correspondingto forces per unit final cross-sectional area (i.e. root growthpressures) of up to 0.1 MPa. As soon as the force on the root was changed there was a rapidreversible compression or extension of the root. Superimposedon this elastic/viscoelastic deformation, the root elongationrate slowed by more than 50% within 30 min of increasing theforce applied to the root by 100 mN. A similarly fast but smallerincrease in growth rate occurred when the force was removed.Both of these ‘fast’ responses were followed bya longer period of more gradual change in the root elongationrate over a period of 20 h or longer. Both ‘fast’and ‘slow’ responses may be explained in terms ofa modified Lockhart model of growth. The initial ‘fast’response of the root is probably due to the immediate changein the effective pressure (i.e. the turgor pressure minus theyield stress and external resisting pressure) available to drivecell elongation. The reason for the second slower adjustmentof the elongation rate is not known, but is probably due tosome combination of a decrease in the rate of cell productionand/or a stiffening of the cell walls in the longitudinal directionwith increasing mechanical resistance. The increase in rootdiameter in response to mechanical impedance decreased the rootgrowth pressure that the root exerted, but was associated witha slower root elongation rate. Key words: Compaction, mechanical impedance, penetration resistance, root diameter, soil strength     

Effects of 2-Chloroethylphosphonic Acid on Growth, Plastid Pigments, and Sucrose Translocation in Radish

2-Chloroethylphosphonic acid (CEPA) caused a significant declinein chlorophyll content of radish plant within 5 d of treatment.Such effects were greater when plants were treated at the two-than at the four-leaf stage. In early treated plants, concentrationof CEPA increasing from 20 mg/1 progressively increased leafweight, while decreasing root (radish) weight. A concentrationof 10 mg/1, applied at the three-leaf stage, increased leafand root weights by 27 and 30 per cent respectively in the cultivar‘Cavalier’. Similar responses were obtained withthe cultivar ‘Cherry Belle’. While Cavalier showeda discrete 10 mg/1 optimum, ‘Cherry Belle’ exhibiteda range of concentrations (10-40 mg/1) optimal for growth. At relatively high concentrations, early application of CEPAcaused inverse changes in sucrose-¹⁴C in the leaves and theroot, so that decreased retention by leaves was accompaniedby increased transport to roots. Low concentrations of CEPAappear promising for growth stimulation in root-crop plants.     

Philosophical Aspects of Measurements, Equations and Inferences in Plant Growth Studies

Growth analysis is based on equations that are ‘identities’because they are algebraically self-evident, whereas the moredeterministic models of plant growth are based on ‘conditionalequations’ that represent quantitative hypotheses. Growthanalytical studies consequently focus on the values of the componentsand not on the validity of the equations, whereas ‘validation’is a prime concern for other growth models. Implications ofmeasurement theory, of dependent and independent variables andof compensating components arise in the use of both types ofequation for quantifying growth. There is now available a rangeof approaches, from traditional growth analysis, through variousdevelopments of growth analysis including light conversion analysis,to complex mechanistic models of growth. Growth analysis, yield component analysis, light conversion analysis, mathematical models, measurement theory, derived quantities, independent variables, equations of growth     

An electrophysiological investigation into the labellar lobe spreading response in the blowfly Protophormia terraenovae

Stimulation of single ‘largest’ or ‘marginal’labellar chemosensilla can evoke ipsi- and contralateral labellarlobe spreading responses in Protophormia. Measurements of reflexlatencies indicate that the response is triggered by messagescoming from the ‘largest’ ipsilateral chemosensilla.Input from the ‘marginal’ chemosensilla would playa role in maintaining the already triggered response.     

Cultivar Differences in the Performance of Bean Seedlings at Suboptimal Temperatures

Growth analysis of plants raised under controlled environments(10–5, 12, 15, 18 and 20 °C, and 21 h photoperiod)was used to examine whether varietal differences in the minimumgermination temperature of four bean cultivars persist duringgrowth at suboptimal temperatures. A method to estimate theminimum vegetative growth temperature, based on axis relativegrowth rate, was developed. In order to compensate for ontogeneticdrift, the harvests were conducted at the same stage of developmentof the plants. Axis relative growth rates, reduction rates ofthe cotyledons and other growth parameters were calculated inorder to compare the cultivars. Cultivar ‘Marschall’showed better growth potential at 12 °C than the others,‘Pergousa‘ at 15 °C, and ‘Marschall’,‘Olsok’ and ‘Pergousa’ at 18 and 20°C. The effect of temperature on axis RGR was similar for‘Marschall’, ‘Olsok’ and ‘Pergousa’(Q₁₀ = 2·1) and more pronounced than for ‘Processor’(Q₁₀ = 1·3). Although there were significant differencesin the growth parameters among the cultivars within each temperatureused, the differences did not correspond with the differencesduring germination at low temperatures. The minimum vegetativegrowth temperature was close to 10 °C for all the cultivarstested. Phaseolus vulgaris L., beans, suboptimum temperature, growth analysis, minimum germination temperature, minimum vegetative growth temperature     

Experimental Studies of the Relation between Carbon Assimilation and Stomatal Movement: II. The Use of the Resistance Porometer in estimating Stomatal Aperture and Diffusive Resistance

Two purely physical sources of error in the ‘resistanceporometer’ as ordinarily used are considered to be ofappreciable importance, viz. that due to the flow through theleaf being augmented with water vapour which is removed againby a drying agent before the air passes through the standardcapillary, and that due to the leaf temperature differing fromthe capillary temperature. In a bad case the total error mightamount to 10 or 15 per cent. of the ‘leaf resistance’. Modifications to deal with these sources of error and with themore important errors due to the responses of the enclosed stomatato variations in CO₂ supply are described.     

Changes in Levels of Naturally Occurring Gibberellin-like Substances during Germination of Seed of Lycopersicon esculentum Mill.

Naturally occurring gibberellin-like substances possessing acidic,basic, and neutral properties were detected, by paper partitionchromatography, in ethanolic extracts of tomato seed and ofetiolated seedlings after 72 and 116 hours' growth. Dwarf maizemutants of the d-1 and d-5 types, ‘Meteor’ pea seedlingsand young ‘Potentate’ tomato plants were used asbioassay material. Hydrolysis of seed and seedling proteinsby ficin in phosphate buffer, pH 6.2, after removal of ethanol-solublesubstances, liberated more and different ‘bound’gibberellin-like substances. It is suggested that protein hydrolysisduring germination is an important means of liberating thesesubstances at different stages of seedling development. Acidic substances were present in all the extracts prepared,but in general two with Rfs 0.25 and 0.55 in iso-propanol: ammonia:water : : 10:1:1 v/v were differentiated on d-2 and d-5 maizerespectively. Neutral substances in dry seed extracts chromatographedin the same solvent, had Rfs of 0.05, 0.35, and 0.95 and thesewere found only in the ethanolic (‘free’) extracts.They were active on d-1 and d-2 maize and ‘Meteor’pea. Basic gibberellin-like substances with Rfs of 0.05 and0.35 were found in ‘free’ extracts of both dry seedand etiolated seedlings after 116 hours' growth which were activeon d-2 maize only. Two others with Rfs 0.45 and 0.95 were extractedfrom seedlings after 72 hours' growth and these were activeon young ‘Potentate’ tomato plants. It is suggested that certain gibberellin-like substances, capableof reversing dwarfism in test plants, may be responsible formorphogenetic or other responses not involving stem extensionin the parent species. Changes were found in the levels of gibberellin-likesubstances but there was no evidence of changes in levels ofseed inhibitors relative to seed growth substances.     

The Influence of the Plant Growth-regulator, 2-Methyl-4-Chlorophenoxyacetic Acid, on the Metabolism of Carbohydrate, Nitrogen and Minerals in Solanum lycopersicum (Tomato)

The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in ‘available carbohydrate’ (starch,‘total’ and ‘reducing’ sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’and roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatments—‘nutrient’(nutrient supply to roots continued after spraying) and ‘water’(distilled water only supplied to roots after spraying) and‘water’ (distilled water only supplied to rootsafter spraying)—the sub-treatments consisting of ‘MCPA’versus ‘no-MCPA’ for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity ‘residualdry weight’ (total dry weight less ‘available carbohydrate’),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe ‘residual dry weight’ basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in ‘residual dry weight’,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram ‘residual dry weight’ of the ‘tops’)was greatly diminished while uptake of total nitrogen and ofP₂O₅ (estimated as increase in total nitrogen or of P₂O₅ ofthe whole plant per day per 1 g. ‘residual dry weight’of the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof ‘available carbohydrate’ as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The ‘tops’ presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the ‘no-MCPA’plants and also of the ‘MCPA-water’ plants showeda steady increase in available carbohydrate, those of the ‘MCPA-nutrient’plants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe ‘available carbohydrate’ supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first ‘flush’ of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium.     

The Influence of Water Deficit on the Factors Controlling the Daily Pattern of Growth of Phaseolus Trifoliates

Phaseolus seedlings were grown in liquid culture under controlledtemperature and irradiance and measurements were made of dailyvariation in growth of the first trifoliate leaves. Leaf growthrate was significantly enhanced within a few hours of the startof the light period. Over a similar time, a small decrease inleaf turgor and an increase in cell wall plasticity were recorded.Slowly declining growth rates as the light period progressedmay have been caused by decreases in turgor during this time.When water availability to the leaves was restricted by growingthe plants for several days in nutrient solution maintainedat a low temperature (12°C), the daily pattern of growthof the trifoliates was changed quite markedly. Dark-growth rateswere slightly enhanced, while light-growth rates were significantlyreduced when compared to growth rates of plants well-suppliedwith water (roots at 20°C). Relative ‘plateau’growth rates of plants well-supplied (ww) with water or sufferinga restricted supply (ws) in the light (L) and in the dark (D)were as follows: ww L > ws D > ww D > ws L. In thelight, turgors of the two groups of plants were similar, suggestingthat the reduced growth rate of the cooled plants resulted froma change in cell wall structure and/or properties. Immediatelybefore the lights were switched on, plants grown with a restrictedwater supply showed relatively high turgors in the trifoliatesand these were presumably responsible for the enhanced growthrates at this time. Restriction of water availability may haveslightly increased the plasticity of cell walls and decreasedthe yield threshold for growth. The control of leaf growth inplants developing water deficit is discussed. Key words: Leaf growth turgor, Cell wall plasticity, Water deficit, Light     

Studies on the Growth in Culture of Plant Cells: I. GROWTH PATTERNS IN BATCH PROPAGATED SUSPENSION CULTURES

Techniques are described for following increases in total cellnumber, fresh weight and dry weight, and changes in mean cellsize, and in the relative number of free cells to cell aggregatesduring the growth of batch-propagated suspension cultures oftissues derived from several species of angiosperms. When totalcell number is plotted against time it is seen that there canbe distinguished in sequence a lag phase, phases of acceleration,maximum rate, and negative acceleration of cell division and,finaly, a stationary phase. Studies with Parthenocissus tricuspidatacrown-gall tissue, growing in a synthetic liquid medium, haveshown that the total cell production per culture in the firstinstance is limited by nitrate supply rather than by the supplyof other inorganic ions, sucrose supply aeration, or the releaseof endogenous inhibibors. Studies, particularly with Acer pseudoplatanustissue, have shown that during the period of high cell-divisionrate, mean cell size reached its minimum value and average numberof cells per cell aggregate its maximum value. Cell separationdoes not occur to a significant extent until cell-division activityhas almost ceased and it is dependent upon cell expansion. Thebalance between cell division and cell expansion determinesthe ‘cellular unit’ composition of the cultures.Refinement of the control of growth patterns in plant suspensioncultures calls for further study of the ‘conditioning’of media, of factors which limit the duration of the periodof high mitotic activity, and of the conditions necessary forfull and rapid cell expansion.     

Mycorrhizal Response of Two Tomato Genotypes Relates to their Ability to Acquire and Utilize Phosphorus

The purpose of this study was to determine how a plant's responseto colonization by mycorrhizal fungi relates to its abilityto acquire and utilize phosphorus for growth and reproduction.Two tomato genotypes previously found to be either responsive(‘LA1709’) or unresponsive (‘large cherry’)to mycorrhizal colonization during early vegetative growth wereexamined in detail. Plants were grown at four levels of addedphosphate or with mycorrhizal inoculum. Vegetative and reproductivegrowth, phosphorus uptake and root length density were measuredduring the course of plant development. Mycorrhizal symbiosissignificantly increased above-ground dry mass, root length,phosphorus content and yield under low phosphorus conditionsin ‘LA1709’, while it had less effect on these characteristicsin ‘large cherry’. When uninfected, however, ‘LA1709’grew and reproduced poorly unless high amounts of phosphoruswere added to the soil, while ‘large cherry’ grewwell under very low phosphorus conditions. This was because‘large cherry’ had significantly higher root lengthdensities than ‘LA1709’, enabling plants from thisgenotype to explore more soil volume and acquire greater amountsof phosphorus when grown without mycorrhizal fungi in low phosphorussoil. ‘Large cherry’ also had higher phosphorususe efficiency and allocated a greater proportion of phosphorusto reproduction when uninfected than ‘LA1709’. Itappears traits that affect a plant's ability to acquire andutilize phosphorus efficiently for growth and reproduction canalso affect its response to mycorrhizal colonization in tomato.Copyright1998 Annals of Botany Company. Tomato,Lycopersicon esculentum,mycorrhiza,Glomus etunicatum,phosphorus, reproduction, lifespan.