Nitrogen Deficiency Slows Leaf Development and Delays Flowering in Narrow-leafed Lupin

Effects of nitrogen (N) supply on leaf and flower developmentinLupinus angustifolius L. cv Merrit were examined in a temperature-controlledglasshouse. Low N supply (0.05 or 0.4 mM N) had little effecton leaf initiation but slowed leaf emergence on the main stemcompared with plants receiving high N supply (6.0 or 6.4 mMN), or with symbiotic N₂-fixation. Plants experiencing transientN deficiency had slower leaf emergence than plants with a continuoussupply of 6.4 mM N. Nitrogen supply did not affect the timeof floral initiation, which occurred within 4 weeks of sowing,by which time nine to ten leaves had emerged. However, the floweringof low-N plants was delayed by 68 to 220 °C d (i.e. 4–14d) even though they had fewer leaves. The effect of N deficiencyon flowering time was largely a result of slower leaf emergence. Lupinus angustifolius L.; nitrogen; leaf; flower initiation; thermal time; plastochron; phyllochron     

Leaf primordia initiation,leaf emergence and tillering in wheat (Triticum aestivum L.) grown under low-phosphorus conditions

In two simultaneous experiments we examined the effects of phosphorus (P) supply on leaf area development in wheat (Triticum aestivum L.) grown in sand with nutrient solutions. In Experiment 1 we studied leaf emergence, leaf elongation, tiller emergence, shoot growth, and P uptake under four levels of P supply (mM) 0.025 (P1), 0.05 (P2), 0.1 (P3), and 0.5 (P4), and. In Experiment 2 there were two levels of P supply, P1 and P4, and we examined the effects of P on leaf primordia differentiation and leaf emergence. The phyllochron was calculated as the inverse of the rate of leaf emergence calculated from the regression of number of leaf tips (PHY-Ltip), Haun index (PHY-Haun), and as the cumulated thermal time between the emergence of two consecutive leaves (PHYtt). The plastochron was calculated from the inverse of the rate of leaf primordia initiation in the apex. P deficiency delayed the emergence of leaves on the main stem and on the tiller 1. Phosphorus deficiency increased the time from emergence to double ridge and anthesis. The final number of leaves was not affected by P. The effects of P on the value of the phyllochron were attributed to both a reduced rate of leaf primordia initiation, and to a reduced leaf elongation rate. P deficiency delayed or even suppressed the emergence of certain tillers. In this work a phosphorus deficiency that reduced shoot growth by 25% at 44 days after emergence significantly modified the structure of the plants by increasing the value of the phyllochron and delaying tillering. These results suggest that any attempt to simulate leaf area development and growth of wheat plants for P-limited conditions should include the effects of the deficiency on leaf emergence.     

The Effects of Copper Supply and Shading on Retranslocation of Copper from Mature Wheat Leaves

Plants of Gamenya wheat (Triticum aestivum L.) were grown inpots of a Cu-deficient sand at two levels of Cu (deficient andsufficient), and harvested on days 13, 22, 28 and 38. In 50per cent of the pots in each Cu treatment, the oldest leaf andleaf 2 of the main stem were shaded when they reached full expansion. The Cu content of the oldest leaf of Cu-sufficient, unshadedplants was high at day 13 and declined rapidly to day 38. Thatof Cu-deficient, unshaded plants was initially relatively lowand declined much more slowly, so that at day 38 it resembledthat of Cu-sufficient plants. Shading the oldest leaf acceleratedthe loss of its Cu in both Cu-deficient and Cu-sufficient plants.The effects of shading and of Cu supply on the loss of Cu fromthe oldest leaf paralleled their effects on the loss of N andchlorophyll. The results suggest that most of the Cu in theoldest leaf does not move out until the leaf senesces. In Cu-deficient plants retention of Cu by old green leaves accentuatedCu deficiency. The release of Cu, resulting from shading theold leaves of Cu-deficient plants, stimulated the growth ofnew leaves. In Cu-sufficient plants, shading depressed growth. copper, shading, retranslocation, wheat, Triticum aestivum L.     

Copper supply and the leaf emergence rate of spring wheat

Copper deficiency can delay flowering and plant maturity. However, the effect of copper deficiency on the rate of leaf emergence has not been quantified. We tested the hypothesis that low copper supply decreases the rate of leaf emergence of wheat (Triticum aestivum L. cv Gamenya). Copper foliar sprays are commonly applied to wheat. We examined the response of the rate of leaf emergence to a foliar application of copper sulphate.Wheat was grown in root cooling tanks (20°C) in the glasshouse. Soil copper treatments were applied as solutions of CuSO₄.5H₂O at three rates: Cu₀=no added Cu, Cu₄₀₀=400 g Cu per 3 kg pot, and Cu₁₆₀₀=1600 g Cu per pot. An additional treatment of a foliar spray of CuSO₄.5H₂O (0.4 mg Cu per plant) was applied to Cu₀ and Cu₄₀₀ plants 45 days after sowing (5.5 leaves on the main stem). Leaves on the main stem were counted and the rate of leaf emergence was estimated from the regression of number of emerged leaves against thermal time (base 0°C). The phyllochron was calculated as 1/rate of emergence.Leaves on Cu₀ and Cu₄₀₀ plants took longer to emerge than on Cu₁₆₀₀ plants, with the phyllochron of Cu₁₆₀₀ plants being 130 compared to 137 for the Cu₄₀₀ plants and 158 for the Cu₀ plants. The foliar application of CuSO₄ at the 5–6 leaf stage resulted in a decrease in the phyllochron of the Cu₀ plants to 127, but no change in that of the Cu₄₀₀ plants.     

Development in wheat as affected by timing and length of exposure to long photoperiod

Seeds of a spring wheat (Triticum aestivum L. cv. ‘Condor’)were vernalized and then grown at 19C in two naturally–litenvironments, one with a moderate (12 h) and the other withlong (18 h) photoperiod. Treatments consisted of transfers ofplants from the moderate to the long photoperiod chamber ondifferent occasions, or for periods of different durations.The main objectives were to determine whether wheat developmentresponds to current and previous photoperiodic environmentsand whether there is a juvenile phase when the plants are insensitiveto photoperiod. Plants under constant 18 h photoperiod had fewerleaves which appeared faster than those under constant 12 hphotoperiod (i.e. phyllochron was increased from 4.4 to 5.1d leaf^–1). Plants transferred from 12 h to 18 h photoperiodat terminal spikelet appearance (TSA) reached anthesis 4 d earlierthan plants retained at 12 h, while plants under continuouslong photoperiod (18 h) completed this phase most rapidly. Thus,there was some evidence for a historic effect of photoperiodon development. Exposure to long photoperiod during the first 5 d after plantemergence accelerated the rate of development towards anthesis,suggesting that there was no juvenile period of photoperiodicinsensitivity. There were, however, changes during ontogenyin the degree of sensitivity to long photoperiod, increasingfrom seedling emergence to a maximum c. 15 d later, and thendecreasing again. Although all treatments were imposed beforeTSA, the response was not limited to the pre-TSA phase, suggestingthat well before the terminal spikelet appeared, the plant wasalready committed to the initiation of this spikelet. Spikeletnumber decreased with delayed transfer to long photoperiod witha minimum for plants transferred to long days from 16-20 d afterseedling emergence. Additionally, there was a trend for an increasein the rate of leaf appearance (decrease in phyllochron) whenthe plants were exposed to long days between 10 and 35 d afterseedling emergence. Although the differences were small, whenconsidered in conjunction with the effects on final leaf numberthey become important in explaining differences in time to anthesis. Key words: Development, flowering, leaf number, photoperiod, phyllochron, Triticum aestivum     

Leaf Blade Dimensions of Rice (Oryza sativa L. and Oryza glaberrima Steud.). Relationships between Tillers and the Main Stem

The effects of genotype and environment on the leaf area indexof rice are well documented, but the rules governing leaf areadistribution among main stem and tillers are less well understood.This study investigated the ontogenetic patterns of leaf bladearea and dimensions on the main stem and tillers of three ricecultivars, IAC47, Javaé (Oryza sativa L.) and CG14 (O.glaberrima Steud.) grown in pots without competition among plants.No differences in phyllochron were observed among culms, butleaves on tillers appeared 0.5 to 0.8 phyllochrons earlier thanthe genealogically corresponding leaves on the main stem (systemof Katayama). Cohorts were thus not fully synchronized. Allculms produced their largest leaves soon after panicle initiation(PI), despite differences in tiller age. Leaves that appearedsubsequently were smaller owing to reduced length but not width,which remained constant. Three different hypothetical rulesgoverning the behaviour of culms were tested: (1) tillers behaveas clones of the main stem; (2) cohorts behave uniformly, and(3) behaviour is determined by leaf position (sum of genealogicalleaf and tiller indices). The results were best explained byhypotheses (2) and (3), with leaf blade width and length showingmarkedly different patterns. Copyright 2001 Annals of BotanyCompany Phenology, phyllochron, leaf area, leaf position, leaf cohorts, summed leaf position, leaf blade length and width     

Effects of soil resistance to root penetration on leaf expansion in wheat (Triticum aestivum L.): composition, number and size of epidermal cells in mature blades

Wheat seedlings {Triticum aestivum L.) were grown on soils withcontrasted resistances to root penetration (measured as penetrometerresistance, R_s. High R_s reduced the rates of leaf appearanceand expansion. Although the duration of expansion was increased,mature leaves were smaller. Underlying changes in leaf anatomywere investigated on cleared mature leaves, focusing on theepidermes. Three leaves were analysed: leaves 1 and 3 whichstarted their development in the embryo, and leaf 5 which wasinitiated on the seedling, after imposition of contrasted soilconditions. In all leaves, high R_s, caused a reduction in maturecell sizes, lengths and widths, and a shift in the relativeproportions of functionally different cell types, with a decreasein the relative proportions of stomata and associated cell types(interstomatal and sister cells) and an increase in the proportionsof unspecialized elongated epidermal cells and of trichomes.In leaves 3 and 5 the number of cellular files across the bladewas also reduced, while in leaf 1 it was similar at the twoR_s. These differences between leaves are attributed to differencesin their developmental stage when root stress was first perceived.Remarkably, R_s had no effect (leaf 1) or relatively small effects(leaves 3 and 5) on the total number of cells per file, suggestingthat this parameter is either largely insensitive to variationin root environment, or is programmed at the outset before stresswas perceived at the apex. Key words: Wheat, anatomy, mature epidermis, root impedance     

Effect of Potassium Deficiency on C3 and C4 Cereals

C₄ cereals (Zea maya L. and Sorghum bicolor L. Moench) and C₃cereals (Triticum aestivum L. and Hordeum vulgare L) were grownin nutrient solutions with constant, interrupted, or absentpotassium supply. The lack of potassium retarded shoot growthand depressed the chlorophyll accumulation in all species ina similar way. After the renewal of potassium, the differencesin the compensation for growth retardation were not correlatedwith the photosynthetic system, but with the recovery of chlorophyllaccumulation in younger leaves. As important for the compensationof shoot growth retardation was a slower senescence of old leavescompared to plants with a constant potassium supply. This wasshown by the chlorophyll content and PEP carboxylase activity.In contrast to C₃ cereals, the C₄ cereals did not react withhigher chlorophyll contents to the same extent after the renewalof the postassium supply. The PEP carboxylase activity, however,was immediately raised higher than in control leaves. Chlorophylland PEP carboxylase activity increased simultaneously only inless aged leaves.     

Flag Leaf Photosynthesis of Triticum aestivum and Related Diploid and Tetraploid Species

Rates of net photosynthesis of the flag leaves of 15 genotypesof wheat and related species were measured throughout theirlife, using intact leaves on plants grown in the field. At thestage when rates were maximal, they were in general highestfor the diploid species, intermediate for the tetraploidspeciesand lowest for Triticum aestivum (means of 38, 32 and 28 mgCO₂ dm^–2 h^–1 respectively). Rates were stronglynegatively correlated with leaf area, leaf width and the meanplan area per mesophyll cell and positvely correlated with stomatalfrequency and number of veins per mm of leaf width. The differencesamong species in these attributes were mainly related to ploidylevel. It was not possible to determine the relative importanceof each anatomical feature, though the changes in stomatal frequencyhad only slight effects on stomatal conductance and the observeddifferences in rates of photosynthesis were much greater thanwould be expected from those in stomatal conductance alone. There was genetic variation in rates of light dependent oxygenevolution of isolated protoplasts and intact chloroplasts butno difference attributable to ploidy. The mean rate, 91 µmolO₂ mg^–1 chlorophyll h^–1, equivalent to 3.9 mg CO₂mg^-1chlorophyll h^-1 was considerably less than the rate of photosynthesisin comparable intact leaves, which was 7.2 mg CO₂ mg^–1chlorophyll h^–1. The total above-ground dry matter yields were least for thewild diploids T. urartu and T. thauodar and the wild tetraploidT. dicoccoides, but the other wild diploids produced as muchdry matter as the hexaploids. The prospects of exploiting differences in photosynthetic ratein the breeding of higher yielding varieties are discussed. Triticum aestivum L., wheat, Aegilops spp, photosynthesis, stomatal conductance, stomatal frequency, polyploidy     

Effects of Constant and Variable Nitrogen Supply on Sunflower (Helianthus annuus L.) Leaf Cell Number and Size

The effects of nitrogen (N) availability on cell number andcell size, and the contribution of these determinants to thefinal area of fully expanded leaves of sunflower (Helianthusannuus L.) were investigated in glasshouse experiments. Plantswere given a high (N =315 ppm) or low (N=21 ppm) N supply andwere transferred between N levels at different developmentalstages (5 to 60% of final size) of target leaves. The dynamicsof cell number in unemerged (< 0.01 m in length) leaves ofplants growing at high and low levels of N supply were alsofollowed. Maximum leaf area (LA_max) was strongly (up to two-fold)and significantly modified by N availability and the timingof transfer between N supplies, through effects on leaf expansionrate. Rate of cell production was significantly (P<0.05)reduced in unemerged target leaves under N stress, but therewas no evidence of a change in primordium size or in the durationof the leaf differentiation–emergence phase. In fullyexpanded leaves, number of cells per leaf (N_cell), leaf areaper cell (LA_cell) and cell area (A_cell) were significantly reducedby N stress. WhileLA_cell and A_cellresponded to changeover treatmentsirrespective of leaf size, significant (P<0.05) changes inN_cellonly occurred when the changeover occurred before the leafreached approx. 10% of LA_max. There were no differential effectsof N on numbers of epidermal vs. mesophyll cells. The resultsshow that the effects of N on leaf size are largely due to effectson cell production in the unemerged leaf and on both cell productionand expansion during the first phase of expansion of the emergedleaf. During the rest of the expansion period N mainly affectsthe expansion of existing cells. Cell area plasticity permitteda response to changes in N supply even at advanced stages ofleaf expansion. Increased cell expansion can compensate forlow N_cellif N stress is relieved early in the expansion of emergedleaves, but in later phases N_cellsets a limit to this response.Copyright 1999 Annals of Botany Company Helianthus annuus, leaf expansion, leaf cell number, leaf cell size, nitrogen, leaf growth, sunflower.     

Morphological Analysis of Leaf and Tiller Number Dynamics of Wheat (Triticum aestivumL.): Responses to Temperature and Light Intensity

In recent literature on Gramineae species, leaf and tiller numberdynamics have been studied by analysing site filling and thephyllochron of the mainstem. However, site filling is influencedby three components: (1) the phyllochron of the mainstem anddaughter tillers; (2) specific site usage (i.e. fraction ofbuds that ultimately develop into a visible tiller at a specificsite); and (3) HS-delay (i.e. difference in Haun Stage (HS)between the parent tiller and daughter tiller above the pointwhere the daughter tiller appears). These three morphologicalcomponents affecting site filling were studied under differentenvironmental conditions in a growth chamber experiment withspring and winter wheat (Triticum aestivumL.). Treatments weretemperature (daily average 10.5, 15.5 or 20.5 °C) and lightintensity (111, 191 or 286 µmol m^-2s^-1). Effects of temperatureand light intensity on phyllochron were well described by equationsalready reported in the literature. Specific site usage washigher at cooler temperatures and greater light intensitiesand was related to tiller position. It is proposed that theseeffects on specific site usage reflect differences in availabilityof local assimilate for tiller appearance. HS-delay of a tillerwas shorter if the expected tiller appearance was later andwas only slightly affected by light intensity or temperature.This new concept, combining HS-delay and specific site usage,can be useful in constructing more general models of the effectsof environmental factors on the dynamics of leaf number andleaf area ofGramineaespecies.Copyright 1998 Annals of BotanyCompany Triticum aestivum; wheat; phyllochron; temperature; light intensity; leaf number; tillering; site filling; site usage.     

A comparison of the impacts of various nitrogen sources on acid-base balance in C3 Triticum aestivum L. and C4 Zea mays L. plants

This work aimed to study the impacts of acquisition and assimilationof various nitrogen sources, i.e. NO₃^–, NH₄⁺ or NH₄NO₃,in combination with gaseous NH₃ on plant growth and acid-basebalance in higher plants. Plants of C₃ Triticum aestivum L.and C₄ Zea mays L. grown with shoots in ambient air in hydroponicculture solutions with 2 mol m^–3 of nitrogen source asNO₃^–, NH₄⁺ or NH₄NO₃ for 21 d and 18 d, respectively,had their shoots exposed either to 320 µg m^–3 NH₃or to ambient air for 7 d. Variations in plant growth (leaves,stubble and roots), and OH^– and H⁺ extrusions as wellas the relative increases in nitrogen, carbon and carboxylatewere determined. These data were computed as H⁺/N, H⁺/C, (C-A)/N,and (C-A)/C to analyse influences of different nitrogen sourceson acid-base balance in C₃ Triticum aestivum and C₄ Zea maysplants. Root growth in dry weight gain was significantly reduced bytreatment with 320 µg m^–3 NH₃ in Triticum aestivumand Zea mays growing with different N-forms, whereas leaf growthwas not significantly affected by NH₃. In comparison with C₃Triticum aestivum, non-fumigated C₄ Zea mays had low ratiosof OH^–/N in NO₃^–3-grown plants and of H⁺/N in NH₄⁺- and NH ₄NO₃-grown plants. Utilization of NH₃ from the atmospherereduced both the OH^–N ratios in NO₃^– -grown plantsand the H⁺/N ratio in NH₄⁺ - and NH₄NO₃ -grown plants of bothspecies. Furthermore, Zea mays had higher ratios of (C-A)/Nin NH₄⁺ - and NH₄NO₃-grown plants than Triticum aestivum. Thismeans that C₄ Zea mays had synthesized more organic anion perunit increase in organic N than C₃ Triticum aestivum plants.Within both species, different nitrogen sources altered theratios of (C-A)/N in the order: NH₄NO₃>NH₄⁺>NO₃^–.Fumigation with NH₃ increased organic acid synthesis in NO₃^–- and NH₄⁺ - grown plants of Triticum aestivum, whereas it decreasedorganic acid synthesis in Zea mays plants under the same conditions.Furthermore, these differences in acid-base regulation betweenC₃ Triticum aestivum and C₄ Zea mays plants growing with differentnitrogen sources are discussed. Key words: Acid-base balance, ammonia, ammonium, nitrate, ammonium nitrate, C₃ Triticum aestivum L., C₄ Zea mays L.     

Responses of Leaf and Tiller Emergence and Primordium Initiation in Wheat and Barley to Interchanged Photoperiod

The influence of constant (9, 13 and 19 h) and reciprocally-interchangedphotoperiods [at terminal spikelet (TS) or triple mound (TM)]on leaf, tiller and primordium development were examined usingphotoperiod-responsive cultivars of spring wheat, ‘UQ189’ and spring barley, ‘Arapiles’. In bothspecies, constant longer photoperiod reduced the duration fromsowing (S) to double ridge (DR), as expected. However, photoperiodsensitivity was not restricted to this mainly vegetative phase.There was also a marked increase or reduction in the durationof reproductive phases between TS/TM and heading (H) when plantswere transferred to shorter or longer photoperiods respectively,compared with controls. These responses were largely independentof the photoperiod during previous phases although minor effectsof the previous photoperiod were observed. For both species,the time course of leaf emergence was linear, or bi-linear,depending on the final leaf number on the main stem. The rateof leaf emergence was faster for the first six to eight leavesthan for the leaves appearing subsequently. The rate of emergenceof early-formed leaves was independent of photoperiod whereasthe rate of emergence of later leaves varied with photoperiod.Photoperiod also affected the dynamics of tillering. The rateof leaf primordium initiation was little affected by variationin photoperiod, but the rate of spikelet initiation increasedwith increases in photoperiod. The rates of leaf and spikeletprimordium initiation were both substantially higher in barleythan in wheat. The fact that the reproductive phase from TS/TMto H was largely independent of the duration of the previousphase provides evidence that this phase might be geneticallymanipulated to increase the time for floret development andhence grain number. Copyright 2000 Annals of Botany Company Photoperiod, rate of development and leaf emergence, tillering, wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)     

The Effects of CO2 Enrichment and Nutrient Supply on Growth Morphology and Anatomy of Phaseolus vulgaris L. Seedlings

Plants of Phaseolus vulgaris were grown from seed in open-topgrowth chambers at the present (P, 350 µmol mol^–1)atmospheric CO₂ concentration and at an elevated (E, 700 µmolmol^–1) CO₂ concentration, and at low (L, without additionalnutrient solution) and high (H, with additional nutrient solution)nutrient supply for 28 d The effects of CO₂ and nutrient availabilitywere examined on growth, morphological and biochemical characteristics Leaf area and dry mass were significantly increased by CO₂ enrichmentand by high nutrient supply Stomatal density, stomatal indexand epidermal cell density were not affected by elevated CO₂concentration or by nutrient supply Leaf thickness respondedpositively to CO₂ increasing particularly in mesophyll areaas a result of cell enlargement Intercellular air spaces inthe mesophyll decreased slightly in plants grown in elevatedCO₂ Leaf chlorophyll content per unit area or dry mass was significantlylower in elevated CO₂ grown plants and increased significantlywith increasing nutrient availability The content of reducingcarbohydrates of leaves, stem, and roots was not affected byCO₂ but was significantly increased by nutrient addition inall plant parts Starch content in leaves and stem was significantlyincreased by elevated CO₂ concentration and by high nutrientsupply Phaseolus vulgaris, elevated atmospheric CO₂, CO₂-nutrient interaction, stomatal density, leaf anatomy, chlorophyll, carbohydrates, starch     

Mixed Nitrogen Nutrition and Productivity of Wheat Grown in Hydroponics

The objective of this study was to study the effects of nitrogen(N) supplied as either mixtures of NO₃ and NH₄ or as all NO₃on the final yield of spring wheat. Two separate greenhouseexperiments evaluated the durum spring wheat (Triticum durumL.) cultivar ‘Inbar’ in 1986, and the hard red springwheat (Triticum aestmum L.) cultivar ‘Len’ in 1987.Nitrogen treatments consisted of all NO, or mixtures (75/25or 50/50) of NO₃ and NH₄. At maturity, plants were harvested,separated into leaves, stems, roots, and grain, and each partanalysed for dry matter and chemical composition Compared to plants receiving only NO₃ as the source of N, mixedN nutrition resulted in greater accumulation of whole plantreduced-N (49 to 108% more), phosphorus (38 to 69% more), andpotassium (25% more) for both cultivars. In all cases, plantsproduced higher grain yields (28% for Len to 78% for Inbar)when grown with mixed N nutrition than with only NO₃. The yieldincrease was not associated with heavier grains or more grainsper ear, but rather with an increase in the number of ear-bearingtillers per plant. For both cultivars, the higher yields withmixed N resulted from the production of more total biomass (36to 76%) as the partitioning of dry matter between plant partswas not altered by N treatment. Under the hydroponic conditionsof this experiment, the utilization of both NO₃ and NH₄ resultedin greater growth, nutrient absorption, and yield than NO₃ alone,which was primarily associated with an enhancement in tillerdevelopment Triticum aestivum L., Triticum durum L., spring wheat, hydroponics, ammonium nutrition, nitrate nutrition, tillering, yield components, partitioning     

Copper Supply in Relation to Content and Redistribution of Copper Among Organs of the Wheat Plant

The relationship of copper supply to the content and movementof copper among organs of wheat plants was examined at sevenstages in their growth from seedlings to maturity on a copperdeficient sand. In the absence of copper (Cu₀), plants becameseverely copper deficient and produced no grain; developmentof tillers, leaves, stems, and inflorescences was delayed andgrowth of roots strongly depressed; leaf senescence was retardedand tiller growth was prolonged. Application of a marginal supplyof copper (Cu₁) overcame all symptoms and promoted growth andgrain production. Increasing copper supply eightfold (Cu₂) didnot change vegetative or grain production. Copper concentrations in stems, individual leaves, and wholetops were highest and responded most strongly to copper supplywhen they were young. As they aged, Cu₁ and Cu₂ leaves lostcopper rapidly; the first Cu₀ leaves retained their copper andremained healthy for more than 7 weeks even though younger leavesdeveloped severe copper deficiency. In all treatments, lossof copper from the oldest leaf paralleled senescence and theloss of nitrogen. It is suggested that copper does not move out of plant leavesuntil they lose organic nitrogen compounds. As a result, copperbehaves in non-senescent leaves as if it is not mobile in plantphloem. But under conditions favouring senescence, copper ishighly mobile: in the present experiment, 67 per cent of thecopper present in vegetative organs of the Cu₂ primary shootat flowering moved from them during grain development and thiscould account for all of the copper found in the grain at maturity. The retention of copper by leaves before senescence, its rapidloss during senescence, and the effect of copper deficiencyin delaying senescence resulted in the oldest leaf of severelydeficient Cu₀ plants in the present experiment having a highercopper concentration than that of copper adequate Cu₁ and Cu₂plants. This behaviour could account for the many reports ofanomalous C-shaped ‘Piper-Steenbjerg’ curves inthe relationship of yield to copper concentrations in planttops. The coupling of copper movement from leaves to nitrogenmovement can also account for the unusually high values reportedfor critical concentrations of copper in tops of plants givenhigh levels of nitrogen fertilizers. Old organs should not be included in samples for diagnosis ofcopper deficiency. Only young organs should be used. In thepresent experiment, the copper concentration of young leavesgave a good indication of the copper status of wheat: a valueof 1 µg g^–1 in young leaves indicated copper deficiency. copper, nitrogen, phloem transport, mineral transport, deficiency diagnosis, wheat, Triticum aestivum L.     

Rate of Leaf Appearance and Final Number of Leaves in Wheat: Effects of Duration and Rate of Change of Photoperiod

This study was conducted to test the hypothesis that photoperiodor its rate of change significantly affects the rate of leafappearance (RLA) and final number of leaves (FNL) in wheat,as suggested from several time-of-sowing experiments. Two wheatcultivars (Condor and Thatcher) were sown in the field on 2Sep. 1992 at Melbourne (38°S). Photoperiod was extendedartificially to give five treatments up to terminal spikeletinitiation (TS) viz.: natural photoperiod (rate of change ofphotoperiod = 2 min d^-1), two faster rates of change (8·5and 13·3 min d^-1) and two constant photoperiods of 14·0and 15·5 h. After TS, the two constant photoperiods wereextended to 15·0 and 16·5 h, respectively, andtreatments were re-randomised, i.e. some plots received differentphotoperiod regimes before and after TS. The rate of leaf appearance maintained strong linear relationshipswith thermal time. It was greater for Condor [0·012-0·013(°C d)^-1] than for Thatcher [0·011-0·012 (°Cd)^-1] and did not alter during plant development or in responseto the change in photoperiod at TS. Rate of leaf appearanceon the main culm was not influenced by the rate of change ofphotoperiod nor by the average photoperiod. Cultivar and photoperiod significantly affected FNL on the mainculm. Condor produced more leaves than Thatcher under long butnot under short photoperiods. The rate of change of photoperioddid not affect FNL independently of the effect of average photoperiod.Most of the variation in FNL due to photoperiod resulted fromdifferences in duration of leaf initiation. The lack of effects of the photoperiod treatments on RLA contrastwith previous reports of its effects on the rate of phasic developmentfrom seedling emergence to double ridge. Therefore, the numberof visible leaves on the main culm (NL) at double ridge andat TS were not constant. However, NL on the main culm at doubleridge was closely correlated with FNL.Copyright 1994, 1999 AcademicPress Triticum aestivum L., wheat, leaf appearance, phyllochron, photoperiod     

Growth Analysis of Solution Culture-grown Winter Rye, Wheat and Triticale at Different Relative Rates of Nitrogen Supply

At low nitrogen (N) supply, it is well known that rye has ahigher biomass production than wheat. This study investigateswhether these species differences can be explained by differencesin dry matter and nitrogen partitioning, specific leaf area,specific root length and net assimilation rate, which determineboth N acquisition and carbon assimilation during vegetativegrowth. Winter rye (Secale cereale L.), wheat (Triticum aestivumL.) and triticale (X Triticosecale) were grown in solution cultureat relative addition rates (R_N) of nitrate-N supply rangingfrom 0.03–0.18 d^-1and at non-limiting N supply under controlledconditions. The relative growth rate (R_W) was closely equalto R_Nin the range 0.03–0.15 d^-1. The maximalR_W at non-limitingnitrate nutrition was approx. 0.18 d^-1. The biomass allocationto the roots showed a considerable plasticity but did not differbetween species. There were no interspecific differences ineither net assimilation rate or specific leaf area. Higher accumulationof N in the plant, despite the same relative growth rate atnon-limiting N supplies, suggests that rye has a greater abilityto accumulate reserves of nitrogen. Rye had a higher specificroot length over a wide range of sub-optimal N rates than wheat,especially at extreme N deficiency (R_N=0.03–0.06 d^-1).Triticale had a similar specific root length as that of wheatbut had the ability to accumulate N to the same amount as ryeunder conditions of free N access. It is concluded that thebetter adaptation of rye to low N availability compared to wheatis related to higher specific root length in rye. Additionally,the greater ability to accumulate nitrogen under conditionsof free N access for rye and triticale compared to wheat maybe useful for subsequent N utilization during plant growth.In general, species differences are explained by growth componentsresponsible for nitrogen acquisition rather than carbon assimilation.Copyright 1999 Annals of Botany Company Growth analysis, nitrogen, nitrogen productivity, partitioning, specific root length, Secale cereale L.,Triticum aestivum L., X Triticosecale, winter rye, winter wheat, winter triticale.     

Kinetic parameters of Zn uptake by wheat are affected by the herbicide chlorsulfuron

Kinetic parameters of Zn uptake were determined for wheat plants(Triticum aestivum cvs Excalibur and Gatcher, and Triticum turgidumconv. durum cv. Durati) pre-grown at deficient or sufficientZn supply and with 0 or 4 mg m^-3 sulphonylurea herbicide chlorsulfuron(2-chloro-N-(((4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino)carbonyl)-benzenesulphonamide].Net Zn uptake generally showed a saturable response to increasingsolution Zn concentrations; this response fitted a modifiedMichaelis-Menten equation incorporating the C_min term (solutionconcentration when net uptake is