Dry Matter Partitioning in a Determinate and an Indeterminate Cultivar of Vicia faba L. Under Contrasting Plant Distributions and Densities

Models for root: shoot, vegetative: generative and stem: leafpartitioning are presented to quantify dry matter partitioningof two contrasting genotypes of Vicia faba, an indeterminateand a ‘topless’. A third plant type, a determinateof which two to three inflorescences had been removed, was alsoincluded but behaved similarly to the intact plant. The root:shoot partitioning model predicts linear relationships betweenroot proportion and the product of air vapour pressure deficitand relative growth rate. Data from field experiments were consistentwith model prediction and coefficients estimated were similarfor both genotypes. Partitioning into pods was modelled as proportionalto the number of actively growing pods younger than 1000°Cd. Coefficients estimated were similar in both genotypes butdifferent between densities and years. In the indeterminategenotype, stem: leaf ratio was allometric throughout, whereasleaf growth ceased but stem growth continued in the determinateafter formation of the terminal inflorescence. Relatively moredry matter was allocated to stems than to leaves in high thanin low densities. In conclusion, the main differences in drymatter partitioning between genotypes concern leaf: stem partitioningduring early pod filling and pod partitioning due to pod numberdifferences. Partitioning, root, shoot, leaf, stem, Vicia faba L.     

Peroxidase Activity in Linum usitatissimum L.

Peroxidase activity was measured at three stages, from seedlingto maturity, in stem tissue of two genotypes of Linum usitatissimum,and their reciprocal F₁ hybrids. The plants were grown throughoutin growth chambers, allowing close control over the environmentalconditions. There were large and consistent differences betweenthe activities of the parental genotypes, and between dialysedand undialysed extracts. Activities in both parents and theF₁ were expressed on a logarithmic scale. The activity of theF₁ fell, with one exception, between the activities of the twoparents. The relationship of F₁ activity to the mean of theparental activities fluctuated with the stage of growth.     

Senescence in Leaves of Acer pseudoplatanus L. and Parthenocissus tricuspidata Planch: 1. Changes in Some Leaf Constituents during Maturity and Senescence

Data are recorded of the changes in chlorophylls, carotene,sugar, shikimic acid, and anthocyanin in leaves of sycamore(Acer pseudoplatanus L.) and Virginia creeper (Parthenocissustricuspidata Planch.) during leaf maturity and senescence. InParthenocissus the losses of chlorophylls, carotene, sugar,and shikimic acid during senescence were closely correlated,and were inversely related to the accumulation of anthocyanin.The losses of chlorophylls, carotene, and sugar by Acer leaveswere also closely correlated. No evidence was found to supportthe suggestion that anthocyanin formation was caused by accumulationof sugar during senescence, but marked differences in shikimicacid content were found between leaves of Acer, which did notform anthocyanin, and Parthenocissus. which did. It is suggestedthat autumn senescence of these leaves involves the rapid senescenceof an increasing proportion of the leaf tissue during a periodof 80 days, and that measurements of the content of constituentsgive an estimate of the proportion of the leaf tissue whichhas senesced.     

Influence of Leaf Age, Soil Moisture, VPD and Time of Day on Leaf Conductance of Various Musa Genotypes in a Humid Forest-Moist Savanna Transition Site

Leaf age effects on the leaf conductance to water vapour diffusionof the adaxial and abaxial leaf surfaces were measured in themorning and in the afternoon on 17 different plantain and banana(Musa spp.) genotypes. The irradiance levels increased three-foldwhile leaf to air vapour pressure deficit levels increased two-to four-fold from morning to afternoon during the sampling periodin a field site located in the humid forest-moist savanna transitionzone of Nigeria. Conductance values were reduced in older, andsenescing leaves relative to the young and mature leaves bothin the morning and in the afternoon. Conductances were higherfor the abaxial leaf surfaces than the adaxial surface and higherin the afternoon than in the morning, with some genotypic differences.Lower values of leaf conductance to water vapour in the afternoonunder a short dry spell was sufficiently variable (P 0·05)among the test genotypes to indicate potential adaptation totransient dry conditions. Differential and relative leaf conductanceadjustments were noted among genotypes experiencing a shortdry spell versus non-limiting soil moisture conditions. Significantgenotypic differences were observed for leaf conductance amongthe 17 genotypes during the afternoon on the lower leaf surfaceof younger leaves. ABB cooking banana cultivars 'Fougamou' and'Bluggoe' might be potentially promising cultivars for transientdry conditions while AAB plantain 'Bobby Tannap' and one ofits hybrids TMPx 582-4 could be very sensitive to short dryspells according to this evaluation.Copyright 1994, 1999 AcademicPress Musa spp., Musa hybrids, adaxial leaf surface, abaxial leaf surface, stomatal response     

Stomatal Response of some Cultivated and Wild Tuber-bearing Potatoes in Warm Tropics as Influenced by Water Deficits

Leaf resistances of 14 cultivated potato genotypes (Solanumspp) and three tuber-bearing wild Solanum species were comparedwhen plants were grown under water stress at two tropical sitesFactors investigated were diurnal changes in leaf resistance,the effect of plant age, transient drought versus well-wateredconditions of potted and field-grown plants These measurementswere carried out in order to determine the stomatal behaviourof tuber-bearing genotypes and species Significant genotypic differences in leaf resistances were notedwithin the cultivated genotypes All genotypes had higher resistanceswhen water-stressed, but LT-7 appeared to have the lowest leafresistances Genetic differences in stomatal behaviour of tuber-bearingSolanum species were confirmed Abaxial stomatal resistancesof water-stressed plants of the species ranged between 1 74and 13 8 s cm^–1 Stomata of S chacoense were less affectedby drought (three-fold) than S tuberosum (four-fold) The greatesteffect was on S jungasense (five-fold) and on S raphanifoliumThese data show that stomata behaviour among tuber-bearing Solanumspecies is sufficiently different to warrant investigationsof drought-resistance in potato species under dry hot conditions Solanum tuberosum L., Solanum raphanifolium, Solanum chacoense, Solanum jungasense, leaf resistance     

Day/night temperature environment affects cell elongation but not division in Lilium longiflorum Thunb

Lilium tongiflorum Thunb. cv. ‘Nellie White’ plantswere grown in different day/night temperature (DT/NT) environmentsto determine the anatomical basis for differential responsesof stem elongation to DT and NT. Lilium plants were forced in1986 and 1987 under 25 and 12 different DT/NT environments,respectively, with temperatures ranging from 14 to 30 °C.Parenchyma and epidermal cell length and width were measuredin stem tissue (1987) and epidermal cell length and width weremeasured in leaf tissue (1986). Total cell number per internodeand vertical cell number per internode were calculated. Stemparenchyma and stem and leaf epidermal cell length increasedlinearly as the difference (DIF) between DT and NT increased(DIF = DT —- NT), i.e. as DT increased relative to NT.DIF had no effect on stem parenchyma width, stem and leaf epidermalcell width, or cell number per internode. Data suggested thatstem elongation responses to DIF are elicited primarily througheffects on cell elongation and not division. Key words: Thermoperiodism, thermomorphogenesis, stem elongation, DIF, cell division, cell elongation, leaf expansion     

Leaf Abscission in Varieties of Phaseolus vulgaris (L. ) and Glycine max (L. ) Merrill/emdash a--Correlation with Propensity to Produce Adventitious Roots

In field trials of Phaseolus vulgaris large differences wereobserved between varieties in the rate at which the leaves abscised.Similar differences were found in the rate of decline of thechlorophyll content of excised leaf discs. A grafting experimentshowed that the differences in leaf abscission depended on thegenotype of the scion and on that of the rootstock. Scion andstock effects of each genotype were similar, and additive. Rootstock/scioncombinations which conferred enhanced leaf retention producedgreater yields of seed and of seed nitrogen. When shoots ofdelayed-senescence genotypes of P. vulgaris were held in waterthey produced more adventitious roots than did shoots of rapid-senescencegenotypes. This relationship between senescence pattern andadventitious rooting was also observed among varieties of Glycinemax, and between isogenic lines of G. max differing in the leafabscission alleles Ab/ab. These results are discussed in relationto current theories of leaf senescence, abscission, and theproduction of yield.     

Development of the Fifth Leaf is Indicative for Whole Plant Performance at Low Temperature in Tomato

In the search for early-detectable selection criteria for growthat low temperature conditions in tomato, first the initiationand growth of individual leaves was analysed. Scanning electronmicroscopy revealed that the first four primordia had alreadydeveloped during the germination period at 25°C. The primordiumof the fifth leaf, however, was initiated after the transferof seedlings to the experimental conditions. The increase inlength of the first three leaves, and to a lesser extent ofthe fourth leaf, was considerably smaller in comparison withthat of later formed leaves. Moreover, the morphology of thefirst three to four leaves was deviant, whereas the others showedthe normal compound leaf architecture. All these results indicatedthat the fifth leaf was the earliest formed leaf with growthcharacteristics that might reflect the growth potential of thewhole plant. Development of the fifth leaf was tested as a marker for wholeplant growth. At three temperature, 18, 15 and 12°C, growthresponses of the fifth leaf were similar to that of whole plantsin four tomato genotypes: Line A, Line B, Premier and MXXIV-13.Significant differences in relative growth rate of dry weightof whole plants and fifth leaves (RGR_W)and of leaf area of thefifth leaves (RGR_LA between two fast growing and two slow growinggenotypes were found. No genotype by temperature interactionfor RGR_W and RGR_LA was found, indicating that the effect oftemperature decrease was similar for the four genotypes. The structure of the mature fifth leaf of one fast and one slowgrowing genotype, Line A and MXXIV-13, was analysed. For bothgenotypes, leaves were small and thick at low temperature, 12°C.The total number of epidermis and palisade parenchyma cellsper leaf was smaller but the size of the cells developed at12°C was larger than at 18°C. Consequently, the slowgrowth at 12°C was due to a low rate of cell division. Atboth temperatures, the fifth leaf to MXXIV-13 was smaller comparedto that of line A. Since the size of the cells were similar,the smaller leaf size was due to lower number of leaf cells. The results confirm the suitability of the growth, especiallyexpressed as RGR_LA , of the fifth leaf as a nondestructive marketfor vegetative development of tomato at low temperature. Growthdifferences between genotypes were mainly reflected by differencesin cell number of leaves, which might be correlated with geneticallydetermined differences in cell number of leaf primordia.Copyright1993, 1999 Academic Press Lycopersicon esculentum Mill. genotypes, plant growth, selection criteria, low temperature, leaf initiation, leaf development, RGR, leaf structure, cell expansion     

Effects of Interactions between Low-temperature Treatments, Gibberellin (GA3) and Photoperiod on Flowering and Stem Height of Spring Rape (Brassica napus var. annua)

Exogenous gibberellin A₃(GA₃) reduced the number of leaf nodesat flowering and time to flowering and increased the stem heightat flowering in three genotypes of spring rape (Brassica napusvar.annua L.). The responses to GA₃were similar to those forlong days (LD) and low-temperature treatments, suggesting thatthe effect of photoperiod and the vernalization response areprobably mediated through gibberellins. The response to exogenousGA₃was greatest in non-cold-treated plants in short days (SD)suggesting that endogenous GAs are limiting in these conditions.CCC, an inhibitor of gibberellin biosynthesis, caused a smallincrease in the number of leaf nodes at flowering and time toflowering and a small decrease in the stem height at flowering,but unexpectedly, its effect was hardly influenced by the applicationof exogenous GA₃. Genotypes that showed the clearest responsesto the treatments with regard to the number of leaf nodes atflowering and time to flowering did not show the clearest responseswith regard to the stem height at flowering; the pattern ofresponses of the number of leaf nodes at flowering and timeto flowering was distinct from that of stem height at flowering.This indicates that flower formation and stem elongation areseparable developmental processes which may be controlled bydifferent endogenous gibberellins, different levels of a specificendogenous gibberellin, or different responses to gibberellin.Copyright 1999 Annals of Botany Company Brassica napus var. annua, gibberellin, photoperiod, spring rape, vernalization.     

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.     

Zinc response in pigeon pea as influenced by genotypic variability

Seven improved cultivars of pigeon pea (Cajanus cajan (L.) Mill sp.) were evaluated at 0 (original Zn deficient soil), 5 and 50 ppm Zn levels under greenhouse conditions. Plants were harvested at 6 weeks after sowing and at maturity. Responses to 5 ppm Zn in shoot at 6 weeks of growth, and in leaf, stem, pod-hull and grain at maturity ranged from 63 to 387, 37 to 116, 15 to 73,9 to 145 and 51 to 200%, respectively. Application of 50 ppm Zn in most of the cultivars did not markedly affect the yield of different plant parts. Zinc concentration at 0 Zn level in shoot at 6 weeks of growth and in leaf, stem, pod-hull and grain of different genotypes varied from 9.8 to 14.5, 13.7 to 21.2, 10.8 to 16.7, 4.17 to 5.83 and 9.2 to 16.7 ppm, respectively, and the increase in concentration with 5 ppm applied Zn ranged from 28 to 248, 28 to 89, 27 to 85, 20 to 142, and 105 to 254 per cent, respectively. The concentration further increased with an increase in Zn level to 50 ppm. There was less variation in the yield and tissue Zn concentration of different genotypes after Zn application. Phosphorus concentration at 0 Zn level in shoot at 6 weeks of growth, and in leaf, stem, pod-hull and grain of different genotypes varied from 0.50 to 0.71, 0.18 to 0.31, 0.11 to 0.24, 0.15 to 0.20 and 0.43 to 0.58% respectively. Zinc decreased P in all plant parts but relative decrease was more in vegetative parts than in grain. The variability in Zn response among pigeon pea genotypes could partly be attributed to the maintenance of proper P/Zn balance in metabolically active plant parts, such as, leaf, and partly to their capacity to exploit soil Zn and to translocate it to the above-ground parts.Contribution from the Department of Soils, Haryana Agricultural University, Hissar (India).     

Developmental Differences in the Location of Polyphenols and Condensed Tannins in Leaves and Stems of Sericea Lespedeza, Lespedeza cuneata

This histologkal study was performed to determine whether differencesin location and concentration of polyphenols and condensed tanninscould be observed in leaves and stems of sericea lespedeza genotypesof high (HP) or low (LP) phenolic content. Polyphenols and condensedtannins were especially evident in the vacuoles of paraveinalmesophyll cells from leaves of both genotypes. However, higherlevels of these substances were observed in paraveinal cellsof HP leaves. Cross-sections through young stem internodes revealedmany perivascular and vascular parenchyma cells staining prominentlyfor polyphenols in both genotypes. Their location in vacuolesof paraveinal mesophyll cells that function in photosynthatetransport within the leaf suggests that these substances playan active role in physiological processes of sericea lespedezaplants. Alternatively, they could represent a form in whichthese plants store excess photosynthates. Lespedeza cuneata (Dumont de Courset) G. Don, sericea lespedeza, polyphenols, condensed tannins, leaf anatomy, stem anatomy     

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     

Protein expression in Arabidopsis thaliana after chronic clinorotation

Soluble protein expression in Arabidopsis thaliana L. (Heynh.) leaf and stem tissue was examined after chronic clinorotation. Seeds of Arabidopsis were germinated and plants grown to maturity on horizontal or vertical slow-rotating clinostats (1 rpm) or in stationary vertical control units. Total soluble proteins and in vivo-labeled soluble proteins isolated from these plants were analyzed by two-dimensional SDS PAGE and subsequent fluorography. Visual and computer analysis of the resulting protein patterns showed no significant differences in either total protein expression or in active protein synthesis between horizontal clinorotation and vertical controls in the Arabidopsis leaf and stem tissue. These results show chronic clinorotation does not cause gross changes in protein expression in Arabidopsis.     

Genotypic Differences in Leaf Water Potential, Abscisic Acid and Proline Concentrations in Spring Wheat during Drought Stress

Recent work with spring wheat has revealed significant genotypicvariation in changes of water potential and abscisic acid (ABA)concentration in response to drought Two experiments with eightspring wheat genotypes have been carried out to check the earlierwork on relationships between water potential and ABA concentrationand to examine causes of genotypic variation in the rate ofdecline of water potential during drought Changes in prolineconcentration were also studied Plants were grown in controlled environment cabinets with nutrientsolution culture and were stressed by withholding water as thefifth or sixth leaf on the main stem emerged. Plants were harvested4, 5 and 6 days after the treatment commenced and measurementsof leaf water potential, stomatal conductance, ABA and prolineconcentrations, and tissue d wts were taken. Significant genotypic variation was found in the decrease ofwater potential with time and in the slopes of linear regressionsof ABA concentration on water potential, confirming earlierresults When differences between leaf areas at the start of the treatmentwere minimised by varying the genotype sowing date significantgenotypic variation in water potentials at harvest was stillobtained. The change in water potential was significantly positivelycorrelated with shoot root d wt ratios at harvest and pre-treatmentstomatal conductances. Proline concentrations were significantly correlated with waterpotential for every genotype, although there was no clear evidenceof genotypic variation in proline concentrations at a givenwater potential The possible role of ABA concentration in drought resistanceof cereals is discussed Triticum aestivum L, spring wheat, water potential, abscisic acid, proline, drought stress     

Susceptibility to purple blotch (Alternaria porri) in garlic (Allium sativum)

Experiments were conducted to study the progress of purple blotch disease of garlic caused by Alternuria porri in the field, to determine the relationship between garlic leaf age and susceptibility to Alternaria porri, and also to assess loss in bulb characters due to purple blotch of garlic. Per cent disease severity and number of purple blotch lesions on four garlic genotypes of known susceptibility, Sel-10 (highly susceptible), G-41 (highly susceptible), IC-49382 (moderately susceptible) and IC-49373 (moderate to less susceptible) were monitored from bulb formation to bulb maturity at weekly intervals. Lesions appeared early on highly susceptible cultivars, Sel-10 and G-41. Rapid progress of disease development was noticed during the last 3 wk before bulb maturity. Peak severity at the maturity of the crop was significantly higher on highly susceptible genotypes. No definite correlation could be established between number of lesions and disease severity. A logistic curve was fitted to predict the disease progress on different weeks before bulb maturity. Levels of leaf tissue found damaged by A. porri at weekly intervals from bulb initiation to bulb maturity were significantly lower on younger leaves than on older leaves. Leaves that emerged 7 wk before bulb maturity required more than a 5 wk period to reach 50% leaf damage, whereas leaves emerging 2, 3 and 4 wk before bulb maturity exceeded 50% leaf damage within a 2–3 wk period. Individual garlic leaves became more susceptible to purple blotch as they aged and emerging leaves were more susceptible the closer they emerged to bulb maturity. Per cent loss in bulb weight and bulb volume was found to be significantly higher on highly susceptible genotypes. No significant reduction in number of cloves/bulb was observed. We propose 4 wk before bulb maturity as the action threshold for initiation of fungicidal application to prevent damaging levels of disease.     

The Effect of Changing Sowing Date on Leaf Structure and Gas Exchange Characteristics of Wheat Flag Leaves Grown under Mediterranean Climate Conditions

Comparisons of leaf structure and gas exchange characteristicshave been made between flag leaves of four old genotypes ofcultivated tetraploid wheats and three current varieties ofhexaploid Triticum aestivum grown under Mediterranean climateconditions. For some genotypes the effect of varying the sowingdate was investigated. In the hexaploid wheat Kolibri the effectof sowing date on leaf structure and gas exchange of the penultimateleaf was also studied. Flag leaves differed significantly in photosynthetic capacityand leaf structure characteristics between genotypes, withineach ploidy level. When the mean values for each ploidy levelwere considered, there were no significant differences in valuesfor photosynthesis per unit leaf area, stomatal conductance,intercellular CO₂ concentration, residual CO₂ conductance andwater-use efficiency between the tetraploid and hexaploid wheatssown on the same date. When comparisons were made of leaf structurethe only significant differences observed were in adaxial andabaxial stomatal frequencies and leaf area: mean values of theseparameters were higher in tetraploid than in hexaploid wheats. The changes in leaf structure in response to varying sowingdate were significant and followed the same pattern in all thegenotypes studied: a xeromorphic adaptation was observed inlater sowings in response to warmer climate. Such structuralchanges affected some gas exchange characteristics. For example,the area of flag leaves decreased by 60% in the hexaploid wheatKolibri from first to last sowing, which led to a transpirativeloss of 49% per single leaf, in spite of the fact that transpirationrate per unit leaf area increased by 26%. Penultimate leavesof cv. Kolibri followed a fairly similar adaptive pattern inlater sowings as compared with flag leaves. The adaptive significanceof changes in leaf structure and gas exchange characteristicswith varying sowing date under Mediterranean climate conditionsis discussed. Key words: Photosynthesis, leaf structure, wheat     

Influence of Endophyte and Water Regime Upon Tall Fescue Accessions. II. Pyrrolizidine and Ergopeptine Alkaloids

Alkaloids, along with specific environmental conditions, havebeen associated with both detrimental and beneficial aspectsof endophyte (Acremonium coenophialum Morgan-Jones et Gams)infected tall fescue (Festuca arundinacea Schreb.) associations.Benefits to the plant accrue through reduced herbivory, whereasdetriment to the animal occurs as altered grazing behaviourand reduced productivity. A controlled environment study wasconducted to examine pyrrolizidine and ergopeptine alkaloidconcentration of four tall fescue accessions as influenced byendophyte status and water regime. Endophyte-free plants weredevoid of ergopeptine alkaloid and contained little, if any,pyrrolizidine alkaloid. Leaf blade tissue of endophyte-infectedisolines contained a range of both ergopeptine (256 to 1633ng g^–1) and pyrrolizidine (92 to 450 µg g^–1)alkaloid concentrations. Water deficit generally increased alkaloidconcentration. Alkaloid yield, based upon concentration andtissue d. wt, showed that significant increase in ergopeptineand pyrrolizidine alkaloid in leaf tissue was associated withwater deficit and was due to actual increased synthesis andnot simply decreased phytomass. Leaf and pseudostem (leaf sheathand stem base) tissue alkaloid concentrations indicated differentaccumulation patterns for ergopeptine and pyrrolizidine alkaloids.Ergopeptine alkaloid yield increased in water-stressed pseudostem,whereas pyrrolizidine alkaloid yield decreased in some, butnot all accessions. The range of host genotype/endophyte biotyperesponse offers the possibility to select associations whichproduce few deleterious effects in animals yet maintain highforage productivity and persistence. Festuca arundinacea, Acremonium coenophialum, tall fescue genotypes, water stress, N-formyl and N-acetyl loline, ergovaline     

The thermal response of leaf extension rate in genotypes of the C4-grassMiscanthus: an important factor in determining the potential productivity of different genotypes

Thermal responses of plant extension rate are reported for 32genotypes of the C₄ grass Miscanthus. Displacement transducerswere used to measure plant extension rate as temperatures werestepped between 20C and 5C. Leaf extension accounted for 83%of the plant extension. The Q₁₀ between 10C and 20C for thegenotypes varied from 3.0 to 4.7. The relationship between temperature(5-20 C) and plant extension rate was found to be describedadequately by fitting a third order polynomial. An estimateof the effect of differences in the thermal response of plantextension rate on the potential yield of the genotypes was calculatedfor Irish climatic conditions using a simple growth model. Potentialyield varied between 3 and 23 t ha^–1 year^–1. Thisdemonstrates the critical role which differences in leaf expansionrate can play in the selection of more productive genotypes.The significance of vapour pressure deficit on the estimatesof thermal response of plant extension rate are discussed. Key words: Leaf growth, Miscanthus, temperature, radiation-use efficiency, vapour pressure deficit, C₄ plants     

Estimates of Stability Parameters in Dioscorea deltoidea Wall

Estimates of stability parameters for various traits in Dioscoreadeltoidea revealed that some characters, such as, per cent diosgenincontent in tubers, stem thickness and leaf breadth were fairlystable traits. Other characters, i.e. tuber length, tuber branchingand petiole length were not stable and were greatly influencedby the environment. The stability of fifteen genotypes variesfrom character to character and six genotypes were found tobe most stable for the majority of the characters. The significantgenotypic regression on the environment indicated that it shouldnot be difficult to breed D. deltoidea strains which shouldperform fairly well under diverse environmental conditions andto recognize the most desirable properties of a genotype tobe released as a variety for wide cultivation. Diosgenin, stable traits, heritable characters, environmental effect, adaptive genotypes