A Method for in Vitro Storage of Lolium multiflorum Lam

A means of storing Lolium multiflorum Lam. stock plants in vitrohas been developed over a period of three years. Variousexplantsand cultureconditions were examined. Shoot tips 0.3–0.9mm long were found to be best for establishing storage culturesbecause they gave a high yield of plantlets in culture and importantpathogens are eliminated. For sub-culturing, after each annualcycle of storage at 2–4 °C, shoot tips, tiller buds,tiller bases and nodes can be used. Tiller buds were most abundantand best for increasing the number of stored plantlets whennecessary. There was no advantage of including an auxin in theculture medium for shoot tips and Murashige and Skoog's mediumwith 0.2 mg l^–1 kinetin has been adopted for initiating,sub-culturing and storing cultures. The optimum temperaturerange for regenerating plantlets was 20–25 °C. Lightwas necessary for a high rate of plantlet regeneration and lightquality and intensity affected their growth. Lolium multiflorum Lam., ryegrass, storage in vitro, tissue culture     

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.     

Variation in Photorespiration in Lolium

The rate of photorespiration in several grass species was shownto be highly variable and dependent on the species, genotype,and conditions under which the plants were grown. Photorespiration,measured as oxygen uptake, was negligible in Cenchrus ciliarisand Paspalum dilatatum but significant in Lolium spp. and Festucaarundinacea. There were significant differences in the rateof photorespiration among plants within a Lolium populationof diverse origin and these differences were independent ofthe conditions under which the plants were grown. Among thetemperate grasses there was a significant correlation betweenphotorespiration and the CO₂-compensation concentration andboth parameters were very low in P. dilatatum. Plants grownin day/night temperatures of 15/10 °C compared with 25/20°C had faster rates of dark respiration but slower ratesof light respiration when measured at the same temperature.Photorespiration was faster than dark respiration although differencesin respiration among plants in the light were not shown in thedark.     

Seed Water Relations and the Regulation of the Duration of Seed Growth in Soybean

Soybean [Glycine max (L.) Merrill] seeds and cotyledons weregrown in an in vitro culture system to investigate the relationshipsbetween cell expansion (net water uptake by the seed) and drymatter accumulation. Seeds or cotyledons grown in a completenutrient medium containing 200 mol m^–3 sucrose continueddry matter accumulation for up to 16 d after in planta seedsreached physiological maturity (maximum seed dry weight). Seedor cotyledon water content increased throughout the cultureperiod and the water concentration remained above 600 g kg^–1fresh weight. These data indicate that the cessation of seeddry matter accumulation is controlled by the physiological environmentof the seed and is not a pre-determined seed characteristic.Adding 600 mol m^–3 mannitol to the medium caused a decreasein seed water content and concentration. Seeds in this mediumstopped accumulating dry matter at a water concentration ofapproximately 550 g kg^–1. The data suggest that dry matteraccumulation by soybean seeds can continue only as long as thereis a net uptake of water to drive cell expansion. In the absenceof a net water uptake, continued dry matter accumulation causesdesiccation which triggers maturation. Key words: Glycine max (L.) Merrill, solution culture, duration of seed growth, water content, dry matter accumulation     

Soya Bean Seed Growth and Maturation by In Vitro Pod Culture

Immature Glycine max (L.) Merr. seeds initially at 50–70mg fresh weight were successfully grown and matured in vitroin detached pods. Surface sterilized pods were floated in aliquid medium containing 5 per cent sucrose, minerals, and glutaminein 125 ml Erlenmeyer flasks and incubated at 25 °C under350–400 µE m^–1 s^–1 white light. Seedswhich were matured in vitro increased tenfold in dry weight,were visually similar to commercial seeds of the same size,were tolerant to desiccation and germinated with normal seedlinggrowth. Excised pods transported dye from the pedicel to thegrowing seed within 120 min. Soya bean pod culture is a usefultechnique to study the influence of single or combinations ofchemical or environmental parameters on regulation of seed growth,seed maturation, and subsequent germination events without theconfounding interactions with the mother plant. Glycine max (L.) Merr., soya bean, pod culture, seed culture, seed growth, seed maturation, germination     

Influence of Genotype, Plant Growth Temperature and Anther Incubation Temperature on Microspore Embryo Production in Brassica napus ssp. oleifera

Eleven F₁ hybrid genotypes of winter rape (Brassica napus ssp.oleifera) were used in a study of induction and growth of microspore-derivedembryos. Plants of each genotype were grown in controlled environmentsat either a constant 15°C or a constant 20°C, both witha 16 h photoperiod. Equal numbers of buds, approximately 2.5mm in length, containing uninucleate microspores were harvestedfrom each genotype and either pretreated (14 d at 4°C) ordissected immediately after harvest. Anthers were cultured onliquid medium based upon that of Murashige and Skoog (1962)and containing 8% sucrose, 0.5 mg dm^–3 naphthylaceticacid and 0.05 mg dm^–3 benzylaminopurine. Anthers fromequal samples of buds were incubated at 35°C for 0, 1, 2or 3 d before transfer to 30°C (21 d) and then 25°C.After a total of 42 d incubation, cultures were scored for thepresence of macroscopic embryos (1–2 mm in length) andfor the presence of anthers containing aborted embryoids whichhad not developed further. The results showed first that bud pretreatment completely inhibitedinduction and secondly that anthers of all genotypes had anabsolute requirement for a 35°C treatment (optimal duration2 d) in order to induce embryoid formation. In the great majorityof genotypes plants grown at 15°C provided more productiveanthers than plants grown at 20°C. However, within eachtreatment there were great differences both in the frequencyof anthers showing induced embryoids and of the final yieldof embryos. There was evidence that hybrids with a common parentresponded similarly under certain treatments. This confirmedthe importance of genotypic control for some components of embryoyield. Key words: Brassica napus, Rape, Anther culture, Pollen, Haploid     

Effects of Temperature and Photoperiod on Phenological Development in Three Genotypes of Bambara Groundnut (Vigna subterranea)

Factorial combinations of four photoperiods (10, 11·33,12·66 and 16 h d^-1) and three mean diurnal temperatures(20·2, 24·1 and 28·1°C) were imposedon nodulated plants of three Nigerian bambara groundnut genotypes[Vigna subterranea (L.) Verdc., syn. Voandzeia subterranea (L.)Thouars] grown in glasshouses in The Netherlands. The photothermalresponse of the onset of flowering and the onset of poddingwere determined. The time from sowing to first flower (f) wasdetermined by noting the day on which the first open flowerappeared. The time from sowing to the onset of podding (p) wasestimated from linear regressions of pod dry weight againsttime from sowing. Developmental rates were derived from thereciprocals of f and p. In two genotypes, 'Ankpa 2' and 'Yola',flowering occurred irrespective of photoperiod and 1/f was controlledby temperature only, occurring sooner at 28·1 than at20·2°C. The third genotype, 'Ankpa 4', was sensitiveto temperature and photoperiod and f was increased by coolertemperatures and photoperiods > 12·66 h d^-1 at 20·2°Cand > 11·33 h d^-1 at 24·1 and 28·1°C.In contrast, p was affected by temperature and photoperiod inall three genotypes. In bambara groundnut photoperiod-sensitivitytherefore increases between the onset of flowering and the onsetof podding. The most photoperiod-sensitive genotype with respectto p was 'Ankpa 4', followed by 'Yola' and 'Ankpa 2'. Therewas also variation in temperature-sensitivity between the genotypesinvestigated. Evaluation of bambara groundnut genotypes foradaptation to different photothermal environments will thereforerequire screening for flowering and podding responses.Copyright1994, 1999 Academic Press Vigna subterranea (L.) Verdc., Voandzeia subterranea (L.) Thouars, bambara groundnut, phenology, photoperiod, daylength, temperature, flowering, podding     

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     

The Effect of Temperature on Growth and Development of Echinochloa Millets

Accumulation of dry weight and leaf plus stem area were measuredin Echinochloa utilis and E. frumentacea grown at temperatureregimes from 15/10°C to 33/28°C (day/night). Tilleringand height were recorded in addition to leaf number which wassubsequently used as a developmental index. In both species shoot dry weight increased with temperatureup to 33/28°C; the increase in relative growth rate (RGR)was negligible above 27/22°C. Below 27/22°C the RGRof E. frumentacea decreased sharply and at 15/10°C it madeno effective growth. At low temperatures the RGR of E. frumentaceawas lower than that of E. utilis due to slow leaf area expansion,and in particular smaller individual leaves. E. frumentaceatillered more than E. utilis. Plant development was retardedat low temperatures but was not as responsive to temperatureas dry weight and leaf area. The different responses to temperatureof the two species were described in equations suitable forinclusion in predictive growth models. Echinochloa spp., millet, growth, development, temperature, relative growth rate     

Effect of Nitrogen Supply on the Grass and Clover Components of Simulated Mixed Swards Grown under Favourable Environmental Conditions I. Carbon Assimilation and Utilization

Simulated mixed swards of Perennial Ryegrass (Lolium perenneL.) cv. S23 and White clover (Trifolium repens L.) cv. S100were grown from seed under a constant 20 °C day/15 °Cnight temperature regime and their growth and carbon economyexamined. The swards received a nutrient solution daily, whichcontained either High (220 mg l^–1) or Low (10 mg l^–1)nitrate N. Rates of canopy photosynthesis and respiration, and final drymatter yields were similar in the two treatments although theproportions of grass and clover differed greatly. The Low-Nswards were made up largely of clover. The grass plants in theseswards had high root: shoot ratios and low relative photosyntheticrates – both signs of N deficiency – and were clearlyunable to compete with the vigorously growing Low-N clover plants.These had higher relative growth rates and dry matter yieldsthan their High-N counterparts. In the High-N swards clovercontributed around 50 per cent to the sward dry weight throughoutthe measurement period despite having a smaller proportion ofits dry weight in photosynthetic tissue (laminae) than grassover much of it. The latter was compensated for, initially bya higher specific leaf area than grass, and later by a higherphotosynthetic rate per unit leaf weight. The results are discussedin relation to observed declines in the clover content of swardsafter the addition of nitrogen fertilizer in the field. Trifolium repens, white clover, Lolium perenne, perennial ryegrass, nitrogen, photosynthesis, carbon balance     

Growth and Nitrogen Fixation by Westiellopsis prolifica Janet

The blue-green alga Westiellopsis prolifica Janet has been isolatedin unialgal bacteria-free culture. Evidence of the ability ofthis algs to fix elementary nitrogen was obtained by demonstrationof increase in total combined nitrogen in cultures by the micro-Kjeldahlmethod and also by the uptake of ¹⁵N as demonstrated by theuse of the mass spectrometer. The growth and nitrogen-fixingcapacity of the alga was studied in relation to temperatureand light intensity. Increase in dry weight was greatest at40° C but the optimum for nitrogen fixation was between30 and 35°C. A considerable proportion of the nitrogen fixedwas released in soluble organic form into the medium.     

Correlative Inhibition in the Shoot of Agropyron repens ( L.) Beauv

Correlative inhibition was investigated in plants of Agropyronrepens at two temperatures. Reciprocal inhibition ocrurred betweenthe main shoot apex and the outgrowing axillary shoots, withthe balance of inhibition varying with temperature. Apical dominancewas stronger at 10 °C than at 20 °C , but even at 10°C release of apical dominance by decapitation had onlyminor effects on the timing of outgrowth, growth pattern andrate of dry weight aocumulation of the axillary shoots. Dominanceof the main shoot apex by the axillary shoots was stronger at20 °C than at 10 °C. Removal of axillary buds preventeddecline in size and activity of the main shoot apex ard resultedin increased rates of primordium initiation, leaf emergenceand dry weight accumulation in the main shoot. It is suggestedthat a system of reciprocal dominance provides a mechanism formaintaining the characteristic habit of the grass plant andlimits growth in height of vegetative shoots. Agropyron repens (L.) Beauv, couch grass, correlative inhibition, apical dominance, shoot, apex     

Growth Analysis of Sweet Pepper (Capsicum annuum L.): 2. Interacting Effects of Irradiance, Temperature and Plant Age in Controlled Conditions

A growth analysis was carried out with sweet pepper plants grownin a phytotron. Irradiance conditions were: 0.84 or 3.25 MJm^–2 in 8 h, 1.67 MJ m^–2 in 16 h and 2.51 MJ m^–2in 24 h. Temperatures applied were 25 or 21 °C during thephotoperiod in combination with 25, 21 and 17 or 21, 17 and13 °C respectively during the nyctoperiod. Highest values for leaf area and total dry weight were foundwhen applying 1.67 MJ m^–2 in 16 h, followed by 3.25 MJm^–2 in 8 h, irrespective of the temperature regime. Continuousirradiance ultimately resulted in leaf drop. A reduction inthe day temperature decreased leaf area and total dry weight.At a day temperature of 25 °C the dry weight increased withdecreasing night temperature when applying 3.25 MJ m^–2in 8 h. At a day temperature of 21 °C leaf area and dryweight were reduced when 17 or 13 °C were applied duringa 16 h nyctoperiod. Values for relative growth rate, net assimilation rate, leafarea ratio and leaf weight ratio strongly decreased with advancingplant age. The effects of irradiance treatment on RGR and NARwere analogous to those on total dry weight while the reversepattern was observed for the LAR. A decrease in day temperaturedecreased the RGR. The effects of night temperature exhibitedstrong interactions with day temperature and photoperiod. Theinfluence of temperature on RGR was largely mediated throughchanges in the LAR. The latter parameter was highly correlatedwith the specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature, plant age     

Response to Temperature in a Stand of Pearl Millet: 10. PARTITION OF ASSIMILATE

Effects of temperature on partition of assimilate between leaves,stems and panicles of pearl millet are analysed in terms ofa duration (t_w) over which a structure increased in weight,and a partition factor (p)—the fraction of new dry matterallocated to the structure during t_w. The value of tw was, forall structures, inversely proportional to temperature abovea base of 10 °C and below an optimum of 28 to 30 °C.For stems and panicles, the value of p was, with one exception,little affected by temperature. The dry weight of these structureswas, therefore, proportional to t_w, and decreased with risein temperature. (The exception was panicles at the lowest temperature,19 °C, for which p was reduced by 40% because few grainswere set.) For leaves, however, p increased with rise in temperature,counteracting the effect on t_w, such that dry weight changedlittle with temperature. The optimum temperature for reproductiveyield was 22 °C, but the proportion of the total dry matterallocated to reproductive structures changed little between22 °C and 31 °C. Key words: Pearl millet, temperature, thermal time, partitioning     

The Effects of Temperature and Form of Nitrogen Supply on the Relative Contribution of Root Uptake and Remobilization in Supplying Nitrogen for Laminae Regrowth of Lolium perenne L.

Plants of Lolium perenne L. cv. S23 were grown in sand culturesupplied with either ammonium (NH₄⁺) or nitrate (NO₃^–)in an otherwise complete nutrient solution at 12°C or 20°C.Three weeks after germination, plants were clipped weekly tosimulate grazing. After 10 weeks growth all nitrogen (N) wassupplied enriched with ¹⁵N to quantify the effects of form ofN supply and temperature on the relative ability of currentroot uptake and remobilization to supply N for laminae regrowth. The form of N supply had no effect on the dry matter partitioning,while at 20°C more dry weight was allocated to laminae regrowthand less to the remaining plant material. The current root uptakeof N, which subsequently appeared in the laminae regrowth, wassimilar for plants supplied with NH₄⁺ or NO₃^–, and bothwere equally reduced at the lower temperature of growth. Remobilizationof N to laminae regrowth was greater for plants receiving NH₄⁺than NO₃^–; remobilization with either form of N supplywas reduced at the lower temperature of growth. Remobilizationwas reduced to a lesser extent at 12°C than current rootuptake. It was concluded that remobilization became relativelymore important in supplying N for regrowth of laminae at lowertemperatures. Key words: Lolium perenne, ammonium, nitrate, temperature, remobilization     

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     

Effects of Root Temperature and Form of Nitrogen Nutrition on Nitrate Reductase Activity in Oilseed Rape (Brassica napus L.)

The effect of root temperature and form of inorganic nitrogensupply on in vitro nitrate reductase activity (NRA) was studiedin oilseed rape (Brassica napus L. cv. bien venu). Plants weregrown initially in flowing nutrient solution containing 10 µMNH₄NO₃ and then supplied with either nitrate or ammonium for15 d at root temperatures of 3, 7, 11 or 17 °C. Shoot temperatureregime was similar for all plants; 20/15 °C, day/night.Root NRA was highest when roots were grown at 3 and 7 °C.In laminae and petioles NRA was highest when roots were 11 or17 °C. The plants supplied with ammonium had much lowerlevels of NRA in roots after 5 d than the plants supplied onlywith nitrate. NRA in the laminae of plants supplied with ammoniumwas low relative to that in plants supplied with nitrate onlywhen root temperature was 11 or 17 °C. Values of the apparent activation energy (E_a) of NR, calculatedfrom the Arrhenius equation, in laminae and petioles were differentfrom roots suggesting difference in enzyme conformation. Evidencethat the temperature at which roots were growing affected E_awas equivocal. Oilseed rape, Brassica napus L., activation energy, ammonium, Arrhenius equation, nitrate, root temperature, nitrate reductase     

Effects of Temperature, Photoperiod and Seed Vernalization on Flowering in Faba Bean Vicia faba

Factorial combinations of three photoperiods (10, 13 and 16h), two day temperatures (18 and 28 °C) and two night temperatures(5 and 13 °C) were imposed on nodulated plants of six diversegenotypes of faba bean (Vicia faba L.). Plants were grown inpots in growth cabinets from both vernalized (1.5±0.5°C for 30 d) and non-vernalized seeds. The times from sowingto the appearance of first open flowers (f) were recorded. Seedvernalization decreased the subsequent time taken to flowerin almost all genotype x growing environment combinations (theexceptions were plants of the cv. Maris Bead grown in threecooler, short-day regimes). The influence of temperature andphotoperiod on the rate of flowering was quantified, using amodel applied previously to other long-day species of grainlegume in which positive linear relations between both temperatureand photoperiod and the rate of progress towards flowering areassumed to apply. A significant positive linear response ofrate of progress towards flowering to limited ranges of meandiurnal temperature was detected in all six genotypes, but inthree genotypes (Syrian Local Large, Aquadulce and Maris Bead)the 28 °C day temperature reduced the rate of progress towardsflowering - suggesting that the optimum temperature for floweringin these genotypes is below 28 °C. In four genotypes (MarisBead, Giza-4, Aquadulce and BPL 1722) a significant positiveresponse to photoperiod, typical of quantitative long-day plants,was observed only in plants grown from vernalized seeds. Incontrast, plants of the genotype Zeidab Local grown from bothnon-vernalized and vernalized seeds showed the same positiveresponse to photoperiod, whereas plants of the land-race SyrianLocal Large were consistently unresponsive to photoperiod. Theimplications of this range of responses amongst diverse genotypesare discussed in relation to screening germplasm. Vicia faba, faba bean, flowering, photoperiod, temperature, seed vernalization, germplasm screening     

The Influence of Donor Plant Genotype and Environment on Production of Multicellular Microspores in Cultured Anthers of Brassica napus ssp. oleifera

Studies of the effects of genotype and pre-flowering environmentalconditions on the production of multicellular microspores wereundertaken th four highly inbred lines of Brassica napus sap.oleifera. These lines were first grown in shaded and unshadedenvironments at 20/15°C arid unshaded at 30/25°C ina daylight phytotron. Buds were harvested from half the plantswhen first visible in the rosette and later from the remainingplants at the time when the first flower opened. The frequencyof microspores at a specific stage of development varied widelywithin a relatively narrow range of bud lengths. Uninucleatemicrospores were not detected in anthers from buds less than1·5 m or greater than 3·0mm long, but were generallypresent in frequencies of greater than 50 per cent in anthersfrom buds which were between 2·0 and 2·5 mm inlength. However, the bud length at which the highest frequencyof uninucleate microspores was detected varied significantlybetween genotypes and between the environments in which theywere grown. Examination of the remaining anthers from each budafter a period in culture revealed that the proportion of microsporesdeveloping into multicellular units varied greatly with budlength, an increase in frequency of multicellular microsporesbeing associated with an increase in the frequency of uninucleatemicrospores in the uncultured anther. Genotypes differed, however,in respect of the relationship between uninucleate microsporefrequency and production of multicellular units. Although thefrequency of multicellular units was as high as 57 percent,further development was limited and the number of embryoldsformed was low in all cases (<10 per cent). The frequency of multicellular units in pollen samples frombuds of a length in which uninucleate microspore frequency washigh varied significantly with genotype, temperature and lightconditions under which donor plants were grown, and the stageof inflorescence development at which buds were removed. Underconditions most conducive to multicellular unit formation (20/15°C,unshaded), the maximum frequency of multicellular units foreach genotype in buds from young inflorescences ranged from11·5 to 56·5 per cent. Shading or exposure tothe higher temperature was associated with a marked reductionin production of multicellular units. Higher frequencies ofmulticellular units were generally detected in microspore samplesfrom younger inflorescences irrespective of genotype or environment. Two of the four inbred lines were selected for a second experimentin which responses to vernalization and photoperiod durationwere monitored. There was a significant reduction in the numberof leaf nodes formed prior to floral initiation in both genotypesfollowing exposure to vernalization and/or a longer photoperiod,the response to photoperiod being more pronounced. Exposureto 4 weeks vernalization was accompanied by a significant increasein the frequency of multicellular units in both genotypes, thefrequency being double that in unvernalized plants under thelonger photoperiod. By contrast, genotypes differed sharplyin their response to photoperiod. In TB 20, the frequency ofmulticellular units was unaffected by an increase in day lengthirrespective of whether seed had been vernalized or not. Onthe other hand, in TB 42 the frequency of multicellular unitswas substantially greater in the 24 h day than in the 12 h day,being 27·3 per cent vs 13·0 per cent in the caseof unvernalized plants and 66·7 per cent vs 18·2per cent in the case of vernalized plants. Brassica napus, anther culture, pollen embryogenesis, genotype-environment interaction     

Grain Yield of Pennisetum americanum Adjusts to Nitrogen Supply by Changing Rates of Grain Filling and Root Uptake of Nitrogen

Coaldrake, P. D., Pearson, C. J. and Saffigna, P. G. 1987. Grainyield of Pennisetum americanum adjusts to nitrogen supply bychanging rates of grain filling and root uptake of nitrogen.–J.exp. Bot 38: 558–566. Pearl millet (Pennisetum americanum(L.)Leeke) was grown in containers at three constant rates of nitrogensupply or with the nitrogen supply increased from the lowestto the highest rate during panicle differentiation or at anthesis.We measured the rate and duration of nitrogen and dry weightgain by individual grains and nitrogen (¹⁵N) uptake by rootsand its distribution during grain filling. The total amountsof nitrogen and dry weight in all grain per plant at the lowestnitrogen supply were 8% and 14% respectively of plants growncontinuously at the highest rate of nitrogen. This was becauselow rates of nitrogen supply reduced grain number, mean grainweight and the nitrogen content of each individual grain. Theamino acid composition of the grain protein was affected onlyslightly by nitrogen treatments. Rates of grain growth were sensitive to nitrogen supply whereasthe duration of nitrogen movement to the grain was not. Nitrogenuptake by roots continued throughout grain filling; rates ofuptake per g root in plants given least nitrogen were one-halfthose of plants given the highest amount of nitrogen. A changefrom lowest to highest nitrogen supply at panicle differentiationincreased the uptake of nitrogen by roots and the rates of growthof individual grains, to the rates observed in plants whichhad been supplied continuously with the highest nitrogen. Whenthe change in supply was made at anthesis there was rapid movementof nitrogen into the plant but this was not translated intomore rapid grain growth. Key words: Nitrogen supply, Pennisetum americanum, grain yield, root uptake