The Growth and Photosynthesis of Seedling Plants of White Clover at Low Temperature

The growth of white clover (Trifolium repens L.) in conditionstypical of April in Southern England (8 °C day/4 °Cnight, 12 h photoperiod of 90 J m^–2 s^–1 visibleradiation) was extremely slow, whether the plants were dependentfor nitrogen on fixation by their root nodules or were suppliedwith abundant nitrate; although growth was slower in the nodulatedplants. The reasons for slow growth were a large root: shootratio and a small leaf area, particularly in the nodulated plants,and a low photosynthetic rate in all plants. The probable effectsof these characteristics on the growth of white clover withgrasses in mixed pastures are discussed. Trifolium repens L, white clover, low temperature, leaf area, photosynthetic rate, nitrogen supply, growth     

Studies in the Physiology of Lichens: With one Figure in the Text: Absorption and Utilization of Some Simple Organic Nitrogen Compounds by Peltigera polydactyla

Peltigera discs can accumulate relatively very large amountsof asparagine from solution by a process which involves theentry and accumulation of asparagine in the tissues as the completemolecule. Utilization of absorbed asparagine occurs at a relativelyslow rate and involves the preliminary deamidation of it toammonia. Asparagine absorption is completely inhibited by sodiumfluoride, and partially inhibited by glucose. Absorption isaccompanied by a release of ammonia in the medium and also byincreases in respiration rates and a change in R.Q. None ofthe absorbed asparagine can be washed out of the tissues. Discsalso show strong powers of absorption from solutions of glutamine,and glutamic and aspartic acids. There is more organic thaninorganic nitrogen in solution in the liquids available to thelichen in its habitat. The amounts of glucose and of phosphate which Peltigera andsome other lichens can accumulate from solution are also verylarge considering the slow growth-rates of these plants. Itis suggested that the possession of strong powers of absorptionof substances from solution may be a general characteristicof lichens and plants of similar habitats: it may representan adaptation to existence in barren conditions where the concentrationof nutrients in solution is very low. Utilization of absorbednutrients at a slow rate may be an adaptation to the need tosurvive long periods of starvation. The ecological implicationsof these suggestions are also discussed.     

The Growth and Reproductive Cycle of Pleurozium schreberi (Brid.) Mitt

The reproductive cycle of the moss Pleurozium schreberi hasbeen investigated by scoring over 600 specimens from Britainand elsewhere, and through regular observations on several populations.P. schreberi is at least functionally dioecious and the stemsare perennial, producing all the inflorescences of a given cycleduring the autumn. On male plants perigonia develop in largenumbers, principally on lateral branches. Relatively few perichaetiaare formed on female stems where they are largely confined tothe main axes. In Britain perigonial development begins in August,the antheridia remaining in the immature stage during the winterresting phase. Young perichaetia are first recorded in Octoberand the archegonia overwinter in the juvenile stage. Rapid gametangialdevelopment takes place in spring prior to the main fertilizationperiod in April and May. Young sporophytes are present fromMay onwards. Setal elongation is delayed until August, but thelate operculum intact stage is reached by October. In Britainthe spores are shed between January and April, nine to twelvemonths after fertilization. Data from the literature and fromFrench, Finnish, and North American specimens suggests a similarcycle in other areas, though with slight differences, notablythat fertilization in parts of Scandinavia may be delayed comparedwith Britain. The results from periodic measurements of marked plants andother techniques suggest that in Britain vegetative growth mayalso show a winter resting phase, stem elongation being recordedonly from April to November.     

More than 400 million years of evolution and some plants still can't make it on their own: plant stress tolerance via fungal symbiosis

All plants in natural ecosystems are thought to be symbioticwith mycorrhizal and/or endophytic fungi. Collectively, thesefungi express different symbiotic lifestyles ranging from parasitismto mutualism. Analysis of Colletotrichum species indicates thatindividual isolates can express either parasitic or mutualisticlifestyles depending on the host genotype colonized. The endophytecolonization pattern and lifestyle expression indicate thatplants can be discerned as either disease, non-disease, or non-hosts.Fitness benefits conferred by fungi expressing mutualistic lifestylesinclude biotic and abiotic stress tolerance, growth enhancement,and increased reproductive success. Analysis of plant–endophyteassociations in high stress habitats revealed that at leastsome fungal endophytes confer habitat-specific stress toleranceto host plants. Without the habitat-adapted fungal endophytes,the plants are unable to survive in their native habitats. Moreover,the endophytes have a broad host range encompassing both monocotsand eudicots, and confer habitat-specific stress tolerance toboth plant groups. Key words: Colletotrichum, fungal endophytes, stress tolerance, symbiosis, symbiotic lifestyle Received 19 June 2007; Revised 25 November 2007 Accepted 30 November 2007     

Biomass Allocation of Erythronium americanum Populations in Different Irradiance Levels

The forest herb Erythronium americanum was collected from threeNew Jersey habitats and grown in 100%, 43%, or 23% glasshouselight to determine if biomass allocation responses to irradiancediffered between populations. Shaded plants had longer petioles,produced fewer runners, and had greater specific leaf areasthan unshaded plants; these responses did not differ significantlyamong populations. All populations produced smaller bulbs whengrown in shade. Over all light treatments, mean leaf area ofplants from a stable, established site was greater than thatof plants from others. In 100 % light, these plants had thegreater bulb growth. The simple architecture of Erythroniummay constrain morphological responses to the light environment. Erythronium americanum(Ker.), forest herb, biomass allocation, light intensity     

On Arborescence in Gahnia clarkei and Gahnia sieberiana

Specimens of Gahnia sieberiana from Brisbane, Queensland, andof Gahnia clarkei from near Orbost, Victoria, were collectedand examined both morphologically and anatomically. The speciesgrow in wet areas and are of interest because they representthe largest arborescent species known in the Cyperaceae. Stemdiameters up to 120 mm and stems up to 10 m long have been observed.Such long stems tend to be supported by nearby vegetation. Althoughfresh stems are tough and woody, they are brittle. Branchingof the stems is sympodial, and numerous branches are producedby plants growing in exposed habitats. There is less branchingin plants from shaded habitats. Basal shoots may also occur.Adventitious roots develop basally on most plants, but withG. sieberiana, some adventitious roots form near the shoot apexand grow in and around leaf bases. Anatomical features of interestare an endodermoid layer composed of sclereids with elongate,undulated, outer tangential walls that are lignified and suberized,short vessel elements with horizontal to oblique simple perforationplates, and relatively short sclereids surrounding vessel elementsin the vascular bundles. Some vascular bundles are bipolar.The presence of short vessel elements here is in marked contrastto the longer tracheary elements in other arborescent monocotyledons. Arborescence, stem anatomy, Cyperaceae, Gahnia, saw sedge, Monocotyledon, bipolar bundles, morphology, endodermoid layer     

The limits and frontiers of desiccation-tolerant life

Drying to equilibrium with the air is lethal to most speciesof animals and plants, making drought (i.e., low external waterpotential) a central problem for terrestrial life and a majorcause of agronomic failure and human famine. Surprisingly, awide taxonomic variety of animals, microbes, and plants do toleratecomplete desiccation, defined as water content below 0.1 g H₂Og^–1 dry mass. Species in five phyla of animals and fourdivisions of plants contain desiccation-tolerant adults, juveniles,seeds, or spores. There seem to be few inherent limits on desiccationtolerance, since tolerant organisms can survive extremely intenseand prolonged desiccation. There seems to be little phylogeneticlimitation of tolerance in plants but may be more in animals.Physical constraints may restrict tolerance of animals withoutrigid skeletons and to plants shorter than 3 m. Physiologicalconstraints on tolerance in plants may include control by hormoneswith multiple effects that could link tolerance to slow growth.Tolerance tends to be lower in organisms from wetter habitats,and there may be selection against tolerance when water availabilityis high. Our current knowledge of limits to tolerance suggeststhat they pose few obstacles to engineering tolerance in prokaryotesand in isolated cells and tissues, and there has already beenmuch success on this scientific frontier of desiccation tolerance.However, physical and physiological constraints and perhapsother limits may explain the lack of success in extending toleranceto whole, desiccation-sensitive, multicellular animals and plants.Deeper understanding of the limits to desiccation tolerancein living things may be needed to cross this next frontier.     

Influence of Soil Moisture on Soil Solution Chemistry and Concentrations of Minerals in the Calcicoles Phleum phleoides and Veronica spicata Grown on a Limestone Soil

Veronica spicata and Phleum phleoides are calcicole plants,mainly occurring on neutral or alkaline soil. An experimentof 16 weeks duration was performed in a glasshouse with theobjective of elucidating the influence of soil moisture levelon soil solution chemistry, and biomass concentrations and uptakeof mineral nutrients by the plants. Seven levels of moisture,corresponding to 35–85% of the water holding capacity(WHC) of the soil, were tested. Soil solution HCO₃, P and Mnconcentrations, and pH, increased, whereas Ca, Mg and Zn concentrationsdecreased, with increasing soil moisture. Concentrations ofK were highest at 50–70% WHC. Concentrations and amountsof P, Zn and Mn in the two species were usually related to soilsolution concentrations; these are elements with low solubilityand availability in calcareous soils. Concentrations of nutrientsin biomass were more influenced by soil moisture in V. spicatathan inP. phleoides . This indicates that P. phleoides is morecapable of controlling its uptake of mineral nutrients, whereasV. spicata is sensitive to variations in soil moisture. It isconcluded that variation in soil moisture regime may greatlyinfluence concentrations of mineral nutrients in calcareoussoil solutions and their uptake by plants. Species able to utilizethese solubility fluctuations may have an advantage in competitionfor nutrients. Variation in soil moisture content might evenbe a prerequisite for adequate acquisition of mineral nutrientsand growth of plants on limestone soils, thereby influencingthe field distribution of native plants among habitats. Copyright1999 Annals of Botany Company Calcareous, calcicole, concentration, mineral, moisture, nutrient, Phleum phleoides, soil, soil solution, uptake, Veronica spicata, water.     

Growth and Survival Responses of Rumex Species to Flooded and Submerged Conditions: The Importance of Shoot Elongation, Underwater Photosynthesis and Reserve Carbohydrates

Plants of Rumex thyrsiflorus Fingerh., R. crispus L. and R.maritimus L., which are zoned along a gradient of elevationin a river foreland ecosystem, and differ in their flood-tolerance,were subjected to different flooding levels. Under conditionsof soil flooding, the growth rates of the flood-tolerant R.crispus and R. maritimus were as high as under drained conditions,but that of the flood-intolerant R. thyrsiflorus was halved.Upon submergence, the low elevation species R. maritimus showedrapid shoot elongation; when elongation resulted in a protrusionof leaves above the water surface, the plants survived. Alternatively,underwater photosynthesis also led to a 100% survival of submergedR. maritimus plants, provided that enough inorganic carbon wasmade available in the water. This could be attributed in partto the use of photosynthetically-derived oxygen for root respiration;in a hydroculture experiment, with 5.0 mM CO₂ in the water inthe shoot environment, photosynthetically-derived oxygen contributedmore than 50% to root oxygen consumption at low oxygen concentrationsin the root environment. The intermediately elevated species R. crispus appeared to bemuch more tolerant towards conditions of prolonged total submergence:older plants survived eight weeks submergence in the dark. Thisresponse was explicable in terms of a dormancy-strategy, whichis characterized by a slow consumption of carbohydrates storedin the tap-root. The differential responses of R. maritimusand R. crispus to total submergence reveal the limitations offlood-tolerance and reflect the different life-histories ofthe species. Key words: Photosynthesis, Rumex, submergence, carbohydrates, growth rate, shoot elongation     

The Significance of Root Starch in Post-fire Shoot Recovery of the Resprouter Stirlingia latifolia R. Br. (Proteaceae)

Stirlingia latifolia, a common shrub of Banksia woodlands ofSW Australia, is a highly successful resprouter species recoveringfrom fire by multiple sprouting of new shoots from its upperroot stock. in comparison with the congeneric fire-sensitive(obligate seeder) species Stirlingia tenuifolia it exhibitsa low shoot:root dry weight ratio and high concentrations ofstored starch in the cortical tissue of its roots. The relationshipbetween root reserves of starch and development of newly sproutingshoot material following fire is examined in S. latifolia afterspring and summer burns. During the initial 2-5 month periodafter fire, levels of stored starch in the roots fall by 50-75%,followed by a slow increase as plants reproduce and the attainmentof pre-fire starch levels by 1·5-2 years after the fire.Starch reserves of roots can be further reduced by shading theregenerating shoots to limit their input of photosynthates andalmost totally eliminated by monthly removal of successive flushesof new shoots over a 10-12 month period. New shoots continueto sprout until all the starch is eliminated. The data are discussedin relation to the fire-induced reproduction of S. latifoliaand its ability to thrive in very frequently burnt habitats.Copyright1993, 1999 Academic Press Fire response, Proteaceae, resprouter, shoot:root ratio, starch storage, Stirlingia latifolia     

Local Differentiation Among Populations of Arabis stelleri var. japonica in a Sand Dune Habitat

Local variation in ecological and genetic traits was analysedin the perennial herb Arabis stelleri var. japonica in a sanddune area in western Japan. Plants of this species are establishedin three contiguous habitats (subpopulations): sand dune, forestand an ecotonal zone between both habitats. Morphological, ecologicaland genetic traits of A. stelleri var. japonica plants wereanalysed to discover the extent of microdifferentiation amongthese subpopulations. All plants in nine quadrats were markedand followed during 2 years. The ecotonal zone presented thehighest number of mature individuals per quadrat. Plants mayproduce the same number of shoots per plant but rosette sizewas larger in plants from sand dune and forest subpopulationsthan the ecotone. Plants in the sand dune showed the highestnumber of large capsules per plant. Mortality of seedlings andmature plants was slightly higher in the ecotone than in theother two subpopulations. Sand dune plants had the highest variationamong quadrats in almost all traits measured. In the electrophoreticanalyses, 21 loci were detected on twelve enzyme systems. Fifteenloci were monomorphic and six loci had 1·2 alleles perloci. Genetic distances and genetic identity Nei's values werevery similar among subpopulations (means I = 0·994, D= 0·006). The total genetic diversity (H_T) was 0·340and the within-population component (H_s) was 0·333 indicatinglow genetic differentiation among subpopulations. Gene flowvaried between genes but most of the values were high (meanNm = 188·3). Subpopulations of A. stelleri showed differentiationin morphological and ecological traits and low genetic differentiationin the loci studied. This may be related with the plastic responseof plants to different microenvironments and a significant geneflow between habitats.Copyright 1994, 1999 Academic Press Arabis stelleri var. japonica, Brassicaceae, gene flow, genetic diversity, local differentiation, mortality, plant population, reproduction     

The Decimation of Endemic Hawai'ian Tree Snails by Alien Predators

Endemic terrestrial tree snails of the Hawai'ian Islands, likethose of other oceanic islands and even some continental areas,are extremely sensitive to disturbance because of their lowpopulation numbers and small geographic ranges. Like many otherplants and animals of oceanic islands, they have evolved nodefenses against introduced predators and competitors. The rangeof Achatinella mustelina, a tree-snail species found only ina short mountain range on the island of O'ahu, typifies thisproblem. Mark-recapture studies at two field locations revealthat the snails exhibit slow growth andlate maturity (3–5years). Fecundity is estimated at about 7 offspring per adultper year. The young are born live at about 4.6 mm. Populationgrowth typically depends on considerable longevity (> 10years). Demographic effects of the depredations by alien predators,rats and a North American predatory snail, Euglandina rosea,were documented in two long-term study sites. The predatorysnail eats all sizes of A. mustelina and can rapidly drive populationsto extinction (less than one year). Rats tend to select largersnails as prey and may leave an area before destroying all ofthe prey snails present; while reproductive output is temporarilydestroyed, populations may survive. Actions necessary to conserveHawai;ian tree snails, or indeed any group of relatively sedentaryinvertebrates with small species ranges, must include predatorabatement, but also preservation and restoration of sufficientlyarge and complex forest habitats that the invertebrates mayfind refuge from alien predators.     

Histochemical Localization of Phenolic Deposits in Leaf Blades of Eragrostis racemosa

The distribution of phenolic deposits in the leaves of Eragrostisracemosa from different habitats was investigated during cultivationunder uniform environmental conditions. The plants retainedtheir leaf phenolic distribution pattern over a period of 8months. Plants from dry habitats had phenolic inclusions inboth epidermal layers, whereas phenolic deposits were absentor only occurred in the abaxial epidermal layers of plants occupyingmoist habitats. Eragrostis racemosa, narrow-heart love grass, Poaceae, phenolic deposits, epidermis, histochemistry, anatomy     

SLUG DAMAGE AND NUMBERS OF SLUGS IN OILSEED RAPE BORDERING ON GRASS STRIPS

In 1995, slug damage and numbers of slugs were estimated intwo grass strips and adjacent rape fields. Investigations beganas soon as rape seedlings emerged and lasted for five weeks.Slug damage to rape plants 1 m from the grass strips was significantlyhigher than at greater distances from the strips. Derocerasreticulatum was the most abundant slug species recorded in bothgrass strips and adjacent rape fields. Arion lusitanicus andArion fasciatus were much less abundant than D. reticulatum.In one field, D. reticulatum declined steadily with increasingdistance from the grass strips and therefore appeared to havecaused the majority of severe damage to rape plants close tothe strips. This finding was surprising because until now severeslug damage in oilseed rape beside semi-natural habitats hasbeen observed only where A. lusitanicus was abundant. (Received 12 November 1997; accepted 26 January 1998)     

Does ABA in the Xylem Control the Rate of Leaf Growth in Soil-Dried Maize and Sunflower Plants?

Maize (Zea mays L.) and sunflower (Helianthus annuus L.) plantswere grown in large volumes of soil and leaf growth rate wasmonitored on a daily basis. Half the plants were given a soildrying treatment and when they showed a significant restrictionof growth rate (compared to both their daily growth rate beforedrying and the average growth rate of well-watered plants onthe same day), leaf water relations were measured and xylemsap was extracted using several techniques. There was a significant negative log-linear relationship betweenthe rate of leaf growth and the concentration of ABA in thexylem for both species. There was no clear relationship betweenleaf growth rate and leaf water potential or turgor for eitherspecies. Assessment of different methods for sampling xylemsap suggests that exudates collected from stem stumps or samplescollected by pressurizing the whole root system are suitablefor estimating ABA concentration in xylem, at least with largeplants of maize or sunflower, provided the first few hundredcubic millimetres of collected sap are used for the assay. Centrifugationof sections of stems resulted in dilution of ABA in the xylemsap with sap squeezed from parenchyma tissue. This is because,at least in plants subjected to mild soil drying, the concentrationof the ABA in the xylem is far higher than that in the cellsap of stem tissue. Results support the proposal that ABA plays a major role asa chemical signal involved in the root-to-shoot communicationof the effects of soil drying. The non-hydraulic restrictionof leaf growth by a chemical signal can be explained by theextra root-sourced ABA in the xylem and may be an importantcomponent of the modification of growth and development whichresults from prolonged soil drought. Key words: Soil drying, ABA, leaf growth, Zea mays L., Helianthus annuus L.     

Inheritance of Chloramphenicol Resistance, a Trait Selected in Cell Cultures of Nicotiana Sylvestris. Speg. and Comes

Three cell lines with improved resistance to growth inhibitionby chloramphenicol were selected from cell cultures of Nicotianasylvestris. Resistance was retained in callus cultures of twoout of three plants regenerated from one of the lines, but notin cultures of plants regenerated from the other two lines.Sexual progeny of the two resistant plants were either sensitiveor showed slow segregation for chloramphenicol resistance. Incallus from only two of the seedlings was inheritance of chloramphenicolresistance clearly demonstrated. Nicotiana sylvestris, cell culture, choramphenicol resistance     

The Influence of Leaf Water Status and ABA on Leaf Growth and Stomata of Phaseolus Seedlings with Hypoxic Roots

The objective of this study was to assess the relative rolesof leaf water status and root-sourced signals in mediating beanleaf responses to root hypoxia. To do so, the roots of beanplants under varied VPD (0.95 kPa to 0.25 KPa) were made hypoxic.Under all conditions, leaf growth rates and stomatal conductanceswere reduced. There was a transitory decline in leaf water potentialat high VPD which accounted for the initial reduction in leafgrowth rates and stomatal conductance. At low VPD, no waterdeficits were detected. Leaf growth inhibition and reduced stomatalconductance under low VPD treatments were unrelated to leafwater status and must be induced by some other factor. In vitrogrowth of leaf discs was reduced by xylem sap collected fromhypoxic roots. Exogenously applied ABA, at high concentrationsin KCl and sucrose, or at low concentrations diluted in xylemsap from aerated plants, inhibited in vitro growth of leaf discs.Applications of ABA in the transpiration stream reduced stomatalconductance.     

The Importance of Light Intensity for Pollen Tube Growth and Embryo Survival in Wheat x Maize Crosses

The success of Triticum aestivumxZea mays crosses, used to producewheat doubled haploids, is influenced by light intensity. Toexamine the basis for this response, pollen tube growth, embryosurvival and indicators of photosynthetic rate were measuredin two wheat cultivars (‘Karamu’ and ‘Kotuku’)crossed with maize at two irradiance levels (250 or 750 µmolm^-2s^-1, PAR). Pollen tube growth was significantly affectedby light intensity in ‘Karamu’ plants but not in‘Kotuku’ plants, despite both cultivars being pollinatedby the same maize source. The percentage of pollen tubes reachingthe cavity between the ovarian wall and integuments, or in themicropyle of ‘Karamu’ plants at high light intensity(65%) was nearly three-times greater than that at low lightintensity (22%). Thus, either low light intensity can affectthe maternal wheat plant in a way that inhibits pollen tubegrowth and/or high light intensity may promote pollen tube growthin ‘Karamu’ plants. Significant differences in ratesof electron transport in plants grown at the two light intensitiesindicated that the rate of photosynthesis may also have an effecton pollen tube growth. These results have importance for improvingthe efficiency of wheat x maize crosses and other wide cerealcrosses. Copyright 2001 Annals of Botany Company Intergeneric hybridization, light intensity, pollen tube growth, embryo survival, Triticum aestivum, wheat,Zea mays , maize     

Survivorship and Spatial Development of Spartina alterniflora Loisel. (Gramineae) Seedlings in a New England Salt Marsh

Patterns of survival and spatial arrangement of tillers of Spartinaalterniflora were examined in natural and in artificially producedbare areas, and in pure stands of adult S. alterniflora in aNew England salt marsh. Seedling growth and survival were highin naturally occurring bare patches and in artificial patches,whether created by continual clipping of adult plants to groundlevel throughout the growing season or by providing bare substrateafter removal of adult plants. Seedling growth and survivorshipincreased with increasing size of bare area. S. alternifloraseedlings were also common in areas dominated by adult plants,but no seedlings survived a whole first growing season underthe mature canopy, probably because of competition from adultplants. In large bare areas, S. alterniflora seedlings grew non-directionally,reaching heights of 0.5 m, and producing as many as 36 tillersin one growing season. Examination of leaf area ratios suggestedthat the production of tillers increased photosynthetic capacityin seedlings with several tillers in contrast to seedlings withouttillers. Thus, seedlings can apparently tiller and colonizefree space radially without a loss of photosynthetic capacity. These results suggest that while seedling success is generallylimited by adult plants in monocultures of S. alterniflora,in disturbed spaces seedling success is high and results ina rapid non-directional proliferation of sexually generatedclones that ultimately preclude the successful invasion of futureseedlings. Clones, directional growth, leaf area ratio, salt marsh cordgrass, seedling survivorship, Spartina alterniflora Loisel     

Effects of Temperature Variation at Different Times on Growth and Yield of Sugar Beet and Barley

Sugar-beet and barley were grown in pots outdoors (environmentN) and, for five successive 4-week periods starting at sowing,batches of plants were transferred to three growth rooms whosetemperatures were either similar to the outdoor mean (environment^M), or 3° C hotter (environment H) or 3° C colder (environmentC). Some plants were harvested immediately after treatment;others were returned to environment N and harvested when mature. At the end of period 1, sugar-beet plants from environment Mhad more dry weight and leaf area than those outdoors. Immediatelyafter spending later periods in environment M, plants had smallerleaves and similar dry weight to those continuously outdoors.These differences disappeared by maturity. Warmth in the growthrooms (i.e. the difference H—C) during periods 1, 2, and3, while leaf area was increasing, increased the number andsize of leaves and usually also dry weight; in later periodsit had no effect. The effects induced during periods 2 and 3,but not period 1, persisted to maturity to give greater totaland root dry weight and yield of sugar. The final effects ondry weight were much larger than those immediately after treatment,and were the result of differences in growth outdoors aftertreatment which depended on differences in leaf area; the efficiencyof the leaves was not affected by previous treatment. Transferring barley to environment M from N had inconsistentimmediate effects on leaf area and dry weight which disappearedby the final harvest. Transfer during periods 2 and 3, beforethe ears had started emerging, increased shoot number and delayeddevelopment. The proportion of the ears that ripened and theyield of grain were usually less for plants that had spent aperiod in environment M than for plants permanently outdoors,which also had some green ears. Warmth in the growth rooms duringperiods 1 and 2 increased dry weight and leaf area immediately,but had negligible effects at maturity because the increasesin leaf area did not persist after ear emergence. Warmth laterhastened death of leaves, decreased total dry weight immediatelyand also at maturity, but increased the proportion of ears thatripened and hence usually grain weight. Variation in leaf areaduration after ear emergence (D), determined by effects on thetime the ears emerged and the rate the leaves died, accountedfor most of the variation in grain yield, but warmth after theears emerged decreased grain yield less than proportionallyto the decrease in D. Net assimilation rate (E) of sugar-beet was greater than ofbarley, and decreased less with age. E of both species was usuallygreater in environment M than outdoors in spite of less radiation.It was only slightly affected by temperature. Nitrogen and potassium uptake were increased by treatments thatincreased dry weight. The percentage contents suggest that extrauptake was a consequence and not a cause of the increase indry weight.