Growth and Dry-weight Distribution in Callistephus chinensis as Influenced by Lighting Treatment

Plants of two cultivars of Callistephus chinensis (Queen ofthe Market and Johannistag) were grown in 8 h of daylight perday with one of the following treatments given during the 16h dark period: (a) darkness—‘uninterrupted night’,(b) I h of light in the middle of the dark period—a ‘nightbreak’, (c) I min of light in every hour of the dark period—‘cycliclighting’, (d) light throughout—‘continuouslight’. The plants receiving uninterrupted dark periods remained compactand rosetted in habit with small leaves, while leaf expansion,stem extension, and flower initiation were promoted in all threeillumination treatments (b, c, d). Although these three treatmentsproduced similar increases in leaf area, continuous light wasthe most effective for the promotion of both stem growth andflower initiation while cyclic lighting was generally more effectivethan a I-h night break. Continuous light also caused more dry matter to be divertedto stems at any given vegetative dry weight and it was shownthat the stem weight ratio of both varieties was correlatedwith stem length.     

Effects of Photoperiod on the Apparent Viscosity of Leaf Cytoplasm in Kalanchoe blossfeldiana: 2. Some Long- and Short-term Effects of Daylength and Spectral Composition of Light

The effects of a range of daylength treatments upon the apparentviscosity of the mesophyll cytoplasm were tested in Kalanchoeand some other daylength-sensitive species by means of a centrifugationtechnique. In Kalanchoe, apparent viscosity increases with increasingshort-day induction, the rise being rapid initially but fallingoff subsequently in the same way as the flowering response.Since the response to light-break treatment is equivalent tolong-day conditions, the effect is truly photoperiodic. Theshort-day increase appears to be only partially reversible uponreturn to long-days. Single leaves may be treated and the effect is not translocatedto the opposite member of a leaf pair. The immediate response to change from light to dark and viceversa is oscillatory; e.g. in the dark an initial fall is succeededby a steep rise and then a more gradual fall in apparent viscosity. Light-breaks with red light are equivalent to white light, andthose with far-red light to darkness. No reversal of red effectsby far-red light has yet been demonstrated. In other species tested, apparent viscosity was significantlyhigher under short-day in Chrysanthemum and Michaelmas Daisy,and under continuous light in Epilobium, i.e. in the daylengthswhich induce flowering. The results are discussed in relationto the present theories of photoperiodism.     

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     

The Relationship between Sugar and Amino Acid Export to the Phloem in Young Wheat Plants

The relationship between amino acid and sugar export to thephloem was studied in young wheat plants (Triticum aestivumL. ‘Pro-INTA, Isla Verde’) using the EDTA-phloemcollection technique. Plants grown with a 16 h photoperiod showeda rapid decrease in the concentration of sugars and amino acidsin the phloem exudate from the beginning of the dark period.When plants grown with a 16 h photoperiod were kept in the darkfor longer than 8 h the free amino acid content in leaves andexudate (on a dry weight basis) increased continually throughoutthe 72 h of darkness. During the first 24 h of darkness thesugars in the phloem exudate decreased to 30% of the initialvalue, and returned to the control level when plants were returnedto light. When plants grown under low light intensity for 10d were transferred to high light intensity, they showed an increasein leaf sugar content (dry weight basis) after 3 d but therewere no differences in leaf free amino acid content (dry weightbasis) compared to low-light plants. The sugar concentrationin the phloem exudate was increased by higher light intensities,but there was no difference in the amino acid concentrationof the phloem exudate, and thus the amino acid:sugar ratio inthe phloem decreased in the high-light plants. The present resultssuggest that amino acids can be exported to the phloem independentlyof the export of sugars. Copyright 1999 Annals of Botany Company Sugar exudation, amino acid transport, nitrogen, phloem, transport, wheat, Triticum aestivum L.     

Diurnal Fluctuations in Growth and CO2 Exchange in Dactylis glomerata

Diurnal fluctuations in dry matter accumulation and leaf extensionof seedlings of Dactylis glomerata were followed through a 16-hlight period and a subsequent 8-h dark period at 20 °C.Themeasured increase in dry weight during the light period andthe decrease during the dark period showed a very good agreementwith calculated dry weight changes derived from the rates ofcarbon dioxide exchange of whole seedlings. Although dry weightof the leaf blades decreased during the dark period, leaf expansioncontinued throughout the 24-h period with associated changesin the ratio of fresh weight to dry weight of the leaf blades.     

Spectral Dependence of Night-break Effect on Photoperiodic Floral Induction in Lemna paucicostata 441

A single dark period of longer than 8 hr induced flowering inLemna paucicostata 441 cultured in E medium. Monochromatic lightsof 450, 550, 650 and 750 nm with a half-power bandwidth of 9nm given for 10 min at the 8th hour of a 14-hr dark period inhibitedflowering. The fluence rates required for 50% inhibition were10, 0.5, 0.1 and 3 µmol m^–2. sec^–1, respectively.When applied between the 4th and the 10th hour of the dark period,lights of 450, 550 and 650 nm were inhibitory showing a maximumeffect at the 8th hour. But 750-nm light completely inhibitedflowering when applied at any time during the first 8 hr ofthe dark period. The inhibitory effect of 750-nm light givenat the beginning of the dark period was totally reversed bya subsequent exposure to 650-nm light, and the fluence-responsecurves for the effect of 750-nm light given at the 0, 4th and8th hour were essentially the same. This suggests that the presenceof P_FR is crucial for the floral initiation throughout the first8 hr of the inductive dark period. The role of phytochrome inthe photoperiodic flower induction of L. paucicostata is discussed. (Received January 4, 1982; Accepted March 19, 1982)     

Rhythmic changes in ribonuclease activity in relation to nucleic acid synthesis in cotyledons ofChenopodium rubrum L. and to floral induction of the plants

Ribonuclease (RNAse) activity was investigated in cotyledons ofChenopodium rubrum plants subjected to various conditions of illumination (photoperiodic induction, continuous light, induction cancelled by interrupting the dark period by a light-break). At the end of the dark period of the single inductive cycles RNAse activity of induced plants was inferior to that of plants grown in continuous light. At the end of the first two cycles the activity was lowest after the interruption of the dark period by light. The investigation of the enzyme in 6h intervals showed rhythmic changes in activity to occur in induced plants. Enzyme activity followed a pattern opposed to this of nucleic acid (NA) synthesis in the cotyledons. In plants from continuous light the enzyme activity did not show any rhythm and in plants having obtained a light-break during the inductive period the rhythm was less distinct than in the induced ones. The period length of the endogenous rhythm of NA synthesis in the cotyledons is about half as long as this of flowering and the peaks of flowering coincide with the throughs of NA synthesis.     

Export, Mobilization, and Respiration of Assimilates in Uniculm Barley during Light and Darkness

The respiratory losses and the pattern of carbon supply froma leaf of unicuim barley were examined during a complete diurnalperiod using a steady state ¹⁴C-labelling technique. After a delay of c. 1 h a portion of the ¹⁴C exported from acontinuously assimilating leaf was lost in respiration in thelight. This respiratory loss amounted to c. 20% of the total¹⁴C fixed. A further 28% of the total ¹⁴C fixed was respiredduring the dark period. In the light, carbon was fixed at a rate of c. 8·9 mgC dm^{–2 h–1} and exported from the leaf at ^c. 5·3mg C dm^{–2 h–1}. Dark export averaged ^c. 31% of theday-time rate. Carbohydrate was stored in the leaf during the day and was almostcompletely remobilized during the dark. Sucrose, the major reservecarbohydrate, was exported first whilst the starch level remainedconstant. After some 9 h of darkness, sucrose declined to alow level and starch remobilization began.     

Biomass Accumulation and Main Stem Elongation of Durum Wheat Grown under Mediterranean Conditions

Detecting and exploiting genetic variation in biomass accumulationis of great importance for increasing wheat yield when the harvestindex is close to its upper limit. This study was undertakento analyse the pattern of biomass accumulation and main stemelongation in 25 durum wheat (Triticum turgidum L. ‘Durum’)genotypes. Field experiments were conducted over 2 years intwo environments contrasting in the amount of available water,in northeastern Spain. Plants were sampled at the main stagesof Zadoks' scale, and dry weight per plant, crop dry weight(CDW) and main stem length were measured at each stage. Measurementsfor growth traits and thermal time from sowing fitted betterto an asymmetric logistic peak curve than to the Richards logisticmodel. Four biological variables were computed from the curve.Differences among curves describing changes in biomass werefound to be greater between irrigated and rainfed sites thanbetween years. Drought stress had less effect on main stem elongationthan on biomass accumulation. Average dry weight per plant andCDW were reduced by drought by 42 and 38%, respectively, duemainly to similar reductions in the mean rate of growth of thetwo variables. In contrast, cycle length from sowing to themaximum values of dry weight per plant and CDW was only slightlymodified by drought. Copyright 2001 Annals of Botany Company Triticum turgidum L. ‘Durum’, durum wheat, biomass, crop dry weight, stem length, rate of growth, modelling, growth analysis, logistic peak curve     

Growth, Development, and Yield of Spring Wheat in Artificial Climates

Spring wheat was grown to maturity in three growth rooms providing:(a) 18 h of light at 20° C and 6 h of darkness at 15°C (hot long days, HL); (b) 18 h of light at 15° C and 6h of darkness at 15° C (cold long days, CL); (c) 14 h lightat 20° C and 10 h of darkness at 15° C (hot short days,HS). Plants were moved between environments at spikelet initiationand anthesis, so dividing the growth period into three. Meanlengths in days of these periods in the different environmentswere: Period 1: HL 16, CL 18, HS 25; Period 2: HL 42, CL andHS 61; Period3: HL 53, CL 83, HS 63. The length of periods 2and 3 also depended on previous treatments. Grain dry weight was affected by environmental differences inall periods and effects in successive periods were additive.Compared with HL, CL or HS in period I before initiation increasedgrain yield by 6 per cent by increasing grain number per ear,HS in period 2 between initiation and anthesis decreased itby 24 per cent by decreasing the number of grains per spikeletand the proportion of spikelets that contained grain; CL inperiod 2 increased it by 21 per cent by increasing the numberof ears; CL in period 3 after anthesis increased it by 16 percent because leaves died later; HS in period 3 decreased itby 14 per cent because there was less radiation and hence lessphotosynthesis. Dry weight of shoot and root at maturity wasincreased by CL or HS in periods 1 or 2, and increased by CLand decreased by HS in period 3. The effects on final yieldof treatment during periods 1 and 2 were the consequence ofsimilar effects already produced at anthesis, and shoot androot dry weight changed little during period 3. The effects of environmental differences on grain dry weightcould not be explained by differences in leaf-area durationafter anthesis (D₃), except that CL in period 3 increased bothyield and D₃ but not proportionately, so that, as with HS inthe same period, grain: leaf ratio was decreased. Environmentaldifferences in periods 1 and 2 appeared to affect grain weightby altering the capacity of the ear to accumulate carbohydrates,determined by the number of grains per ear, rather than by alteringthe supply of carbohydrates, determined by D₃. There were some interactions between environments in differentperiods which were usually small compared with the main effects.     

Effect of Source-to-sink Ratio on Partitioning of Dry Matter and14C-photoassimilates in Wheat during Grain Filling

Increasingly, wheat (Triticum aestivumL.) is being grown intropical environments, but there is inadequate information aboutthe physiological processes limiting yield. In this investigation,the source:sink ratio was manipulated to examine the performanceof source-sink interactions after anthesis and the factor(s)limiting grain filling in tropical conditions. Plants of threewheat cultivars, Cuba C-204, Candeias and IAC-60, were artificiallymodified to give different source:sink ratios. The treatmentswere: I, Control; II, all spikelets on one side of the spikeremoved; III, all spikelets removed except the four centralspikelets of the spike; and IV, flag leaf blade removed. Thedistribution of dry matter between kernels and stem internodeswas analysed at harvest in all three cultivars. Partitioningof¹⁴C-photoassimilates was measured on three occasions afteranthesis in the cultivar Cuba C-204. Modifications of source:sinkratio led to different patterns of allocation of dry matterbetween cultivars and sowing dates. The reduction in sink sizein treatment II produced no significant change in the mass pergrain in the January sowing, but this was enhanced in two cultivarsin the November sowing. In treatment III, both mass per grainand translocation of¹⁴C-photoassimilates declined, apparentlydue to feedback inhibition of photosynthesis. The participationof stem reserves in grain filling and the existence of genotypicdifferences in response to availability of photoassimilateswere corroborated. The pattern of partitioning of dry matterobserved in plants in this investigation suggests a source limitation,particularly during the November sowing. This pattern differedmarkedly from that in other studies, most of which have beenmade in temperate areas.Copyright 1999 Annals of Botany Company Photoassimilates, sink, source, partitioning, grain filling, wheat.     

Perithecial formation in Gelasinospora reticulispora III. Inhibitory effects of near-UV and blue light during the inductive dark period

Growing hyphae of Gelasinospora reticulispora required a continuousdark period prior to photoinduction of perithecia. The inductivedark period was interrupted by brief exposure of the hyphaeto white light so that the formation of perithecia no longertook place. Photosensitivity of the hyphae in terms of the light-breakeffect gradually changed during the inductive dark period. Sensitivityreached its maximum at the 18th hr of the dark period when anirradiation of 1?10⁵ ergs cm^–2 of near-UV light or 4?10⁴ergs cm^–2 of blue-light was sufficient for the light-break.Red and far-red light had no effect at all. The light-breakeffect was limited to the irradiated portion of the hyphae anddid not affect any unirradiated portions. Inhibitory effecton perithecial formation of continuous white light could betotally replaced for several days with intermittent irradiationof near-UV or blue light if given for 5 min every 4 hr. (Received December 18, 1973; )     

Variation in the Photoperiodic Control of Flowering of Two Cultivars of Antirrhinum majus L.

The susceptibility to photoperiodic induction of an early (PinkIce) and a late (Orchid Rocket) flowering variety of Antirrhinummajus was investigated. At various times during developmentplants of both varieties were subjected to 1, 2, 3 or 4 long-daycycles. The early variety became increasingly more responsiveto long-days while the late variety showed no positive responsethroughout the course of the experiment. One hour light-breaksgiven midway through the 16-h dark period evoked a decreasein the leaf number of Pink Ice plants. The leaf areas of bothvarieties increased to levels equivalent to long-day grown plants.The net CO₂ uptake of plants grown in light-breaks increasedin proportion to the increase in leaf area. However the specificuptake of CO₂ per unit area was similar for light-break andshort-day grown plants but was substantially lower than thelong-day plants. Suggestions are made to explain the differencesin photoperiodic response of the two varieties in terms of variationin assimilation rate.     

Changes in the Free Amino Compounds in Young Tomato Plants in Light and Darkness with particular Reference to {gamma}-Aminobutyric Acid

Tomato plants were grown to the five-leaf stage under uniformconditions in a growth room with a daily light period of 15h. Plants were sampled at intervals through 24 h periods andthe free ninhydrin-positive compounds determined in roots, bleedingsap, stems and shoots (mainly leaves), using ion-exchange columnchromatography and a lithium-buffer separation system. The compoundspresent and their range of concentrations are given for twooccasions: after illumination for 8 hand after 5 h of darkness. Data for -aminobutyric acid (GAB), glutamic acid, glutamine,alanine, aspartic acid and ammonia are summarized graphicallyfor all occasions and for all parts of the plant; asparaginefor sap only. The data were examined for correlations betweenthese substances for both light and dark conditions. Relative amounts of free acids were: root glutamine> glutamicand GAB > aspartic > alanine; bleeding sap glutamine >asparagine > GAB > aspartic> alanine; stem glutamine> glutamic > GAB and aspartic > alanine; shoot (leaf)GAB and glutamine > aspartic > alanine and glutamic. Patternsof change were as follows: in the root GAB and glutamic weresimilar and unlike glutamine; alanine did not change;sap ammonia,GAB and alanine were parallel, glutamine was similar to theseonly in light; in the stem glutamine and glutamic tended toaccumulate in parallel in light, but GAB did not; in the shoot(leaf) GAB and glutamine were similar except that the formeraccumulated more rapidly in the initial light period; glutamicacid and alanine were similar to each other but distinct fromGAB and glutamine. The relatively large amounts of GAB in tomato plants and themagnitude of the changes occurring in light and darkness seemindicative of its importance as a temporary storage productfor protein amino acids, but the factors controlling accumulationand utilization in different parts of the plant are unknown.     

Pathway of dark inorganic carbon fixation in two species of diatoms: influence of light regime and regulator factors on diel variations

Planktonic algae submitted to vertical mixing with a short periodicitycommute many times a day from low to high irradiance levels.To study the influence of this light periodicity, two diatoms,Skeletonema coslatum and Nitzschia turgiduloides, were cultivatedunder alternating conditions of 2 h light/2 h dark (2 h/2 h),simulating vertical mixing in the natural environment. Two otherlight regimes were used: continuous light (CL) and alternatecycles of 12 h light/12 h dark (12 h/12 h). Products synthesizedin the dark by S.costmum during 60 s incubation for 2 h/2 hculture or during 5 min for 12 h/12 h culture were determined.They were essentially sugars, malate, aspartate and glyceratefor 2 h/2 h cells and 12 h/12 h cells taken at the beginningof the light period. In contrast, 12 h/12 h cells taken duringthe darkness or in the middle of the light period and set inthe dark synthesized only amino acids. Our results corroborateprevious reports on dark CO₂ fixation via phosphoenolpyruvatecarboxykinase (PEPCKase, enzyme allowing the fixation of CO₂on PEP and the synthesis of amino acids) with involvement ofa substrate synthesized during the light period, but demonstratethat incorporation also occurs by the C-3 pathway (pathway responsiblefor the major CO₂ fixation in the light) in the very early stagesof the dark period. Another important result highlighted bythis study is the appreciable rate of dark fixation: on average6.7, 8.3 and 12.7% of photosynthesis at saturating photon fluxdensity for N.turgiduloides cultivated under 2 h/2 h, CL and12 h/12 h regime respectively and nearly 12% for S.costatumin the 2 h/2 h light regime. Variation of dark fixation wasinvestigated as a function of hour in the two species. Skeletonemacostatum cells submitted to the 2 h/2 h cycle show a constantrate of light-independent assimilation throughout the day. Bycontrast, both N.turgiduloides grown under the 12 h/12 h or2 h/2 h regime and S.costatum cultured under the 12 h/12 h cycleundergo fluctuations in the rate of dark fixation over the light/darkcycle. The mean dark fixation rate is controlled by the lengthof the photoperiod or the frequency of light fluctuations, dependingon species. We argue that this phenomenon must be taken intoconsideration in primary production calculations. Dependingon whether they are synthesized at the beginning or at the endof the light period, products are somewhat different and therate of fixation varies. This leads us to suggest that the pathwayof dark fixation may be regulated by at least two factors: amountof available substrate and enzyme (RuBPCase and PEPCKase) activityand/or amount.     

Influence of Carbohydrates on Photosynthesis in Single, Rooted Soybean Leaves Used as a Source-Sink Model

The single rooted leaf of soybean (Glycine max L. Merr.) wasused to study source-sink relationships in photosynthesis. Whenthe leaves were kept under a regime of 10 h light (410–480µmol photons m^–2, 400–700 nm)–14 h dark,they did not expand, the increase in leaf dry weight almoststopped, and photosynthetic activity remained at a high andconstant level for 8 d while the dry weight of the roots increasedat a constant rate throughout the period. Thus, under this conditionthe leaf and the root system served as the only source and sinkorgans, respectively. When leaves grown for 7 d under this conditionwere placed under continuous light to alter the source/sinkbalance in photosynthate, the root dry weight increased at aconstant rate equal to that found under the 10 h light–14h dark condition. The leaf dry weight markedly increased andby day 5 of continuous light had increased 1.6-fold, mainlyas a consequence of accumulation of starch and sucrose, whichwere not translocated for root growth. The continuous lightcaused an abrupt decrease in the photosynthetic activity (40%of initial value by day 5). However, the activity recoveredalmost completely after a 32-h transfer to darkness. Significantnegative correlations existed between photosynthetic activityand the sucrose and starch contents in the rooted leaves placedunder continuous light. When the plants were treated with variouslight conditions, there was no significant difference (p<0.01)among the regression line slopes for photosynthetic activityon the sucrose content, but there was some deviation among thosefor the photosynthetic activity on the starch content. Thisresult suggests that sucrose accumulated in the leaf has a moredirect influence on photosynthetic activity when the source/sinkbalance was altered. (Received September 9, 1985; Accepted February 21, 1986)     

Floral Induction of Xanthium strumarium in Long Days

An efficient method of inducing flowering in the normally strictshort-day plant, Xanthium strumarium L., in long days is described.Plants were grown in 16-h long days and subjected to two thermocycleswith a root application of gibberellic acid at the 8th h ofthe light period. A thermocycle was defined as follows. Forthe first 8 h of the 24-h cycle, the temperature was 4 °C;for the remaining 16 h, it was 23 °C. The light was on forthe first 16 h and off for the remaining 8 h. Xanthium strumarium L., floral induction, thermoperiod, gibberellic acid     

SUCCESSIVE PROCESSES INVOLVED IN THE GERMINATION RESPONSE OF NASTURTIUM SEEDS

1. The seeds ofNasturtium palustreDC. do not germinate, eitherin the light or darkness, at various constant temperatures,but require for their full germination a certain period of alow temperature (5°) applied immediately after light irradiation.These results indicate the existance of at least two processes,a light-dependent process and a low temperature-requiring process,in the initiation of germination ofNasturtiumseeds. Experimentalevidence indicated further that the light exposure causes twodifferent processes in the seed germination. 2. When a dark period at 23° was inserted between the lightirradiation and the low temperature treatment the germinationwas suppressed. The inhibitory effect of the inserted dark periodat 23° was eliminated by a short irradiation during thedarkness (light-break). 3. Prolonged exposure ofNasturtium seeds to any concentrationof gibberellin brought about no germination when exposure wasgiven in complete darkness. The germination was promoted onlywhen light irradiation was applied to the seeds. A short applicationof gibberellin at a fairly high concentration was, however,remarkably effective for the germination even in the darkness,and the germination was inhibited as the gibberellin applicationwas lengthened. It was considered that gibberellin could substitutefor the combined effect of light irradiation and low temperaturetreatment to induce the germination of Nasturtium seeds, andthat gibberellin was inhibitive toward the reactions followingthe above treatments which induced the germination (Received October 31, 1996; )     

Flower Opening in Asiatic Lily is a Rapid Process Controlled by Dark-light Cycling

In commerce, Asiatic lilies are picked in bud, each stem holdingseveral buds. We found flower opening was rapid, taking lessthan 4 h both on the stem and for excised buds. Opening wasalso strongly synchronous. For a 12 h day-night cycle, openingbegan late in the dark period, reaching a mid-point after 11h of darkness. This was equally true of buds that were excisedwhen nearly ready to open, and those with 3–4 d of developmentto complete. Reversing day and night reversed the time of opening,and red light was as effective as white light in providing ‘day’conditions. A 15 min light break during the night did not affectthe opening. Lengthening the night (8, 12, 16 h) and shorteningthe day delayed opening from 9, to 11, to 13 h after the startof darkness, respectively. In continuous light and continuousdark, synchronicity was lost. If opening flowers were held inextended darkness, two phases of opening could be discriminated.In a ‘dark phase’, petals opened to approx. 40°,and anthers remained intact. When such flowers were returnedto light, there was a ‘light phase’, where petalsopened further, became more pigmented and began to recurve,and the anthers dehisced, these events taking only 2–3h. The net result was that flowers became fully open and anthersdehisced approx. 2 h after dawn, regardless of daylength. Copyright2000 Annals of Botany Company Asiatic lily, Lilium hybrid, flower opening, timing, endogenous rhythm, synchronicity     

Effects of Low Temperature on Growth and Nutrient Accumulation in Rye (Secale cereale) and Wheat (Triticum aestivum)

Rye (Secale cereale cv. Rheidol) and wheat (Triticum aestivumcv. Mardler) were grown at shoot/root temperatures of 20/20°C (warm grown, WG plants), 8/8 °C (cold grown, CG plants)and 20/8 °C (differential grown, DG plants). Plants fromcontrasting growth temperature regimes were standardized andcompared using a developmental timescale based on accumulatedthermal time (°C d) at the shoot meristem. Accumulationof dry matter, nitrogen and potassium were exponential overthe time period studied (150–550 °C d). In rye, therates of plant dry matter and f. wt accumulation were linearlyrelated to the temperature of the shoot meristem. However, inwheat, although the rates of plant dry matter and f. wt accumulationwere temperature dependent, the linear relationship with shootmeristem temperature was weaker than in rye. The shoot/rootratio of rye was stable irrespective of growth temperature treatment,but the shoot/root ratio of wheat varied with growth temperaturetreatment. The shoot/root ratio of DG wheat was 50% greaterthan WG wheat. In both cereals, nutrient concentrations anddry matter content tended to be greater in organs exposed directlyto low temperatures. The mean specific absorption rates of nutrientswere calculated for the whole period studied for each species/temperaturecombination and were positively correlated with both plant shoot/rootratio and relative growth rate. The data suggest that nutrientuptake rates were influenced primarily by plant demand, withno indication of specific nutrient limitations at low temperatures. Nutrient accumulation, relative growth rate (RGR), rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat