Influence of paclobutrazol on growth and development of fruit in Brassica juncea (L.) Czern and Coss

Foliar spraying of paclobutrazol(5, 10 and 20 g mL^–1) on Brassica juncea (cv. RLM 514) plants, at the green floral bud stage of the terminal inflorescence, exerted a profound effect on growth and metabolism of fruits (siliquae). Paclobutrazol caused a decrease in siliqua length but enhanced significantly siliqua width, seed size (diameter) and seed number per siliqua. Paclobutrazol increased dry matter production and also hastened the relative growth rate of the siliqua wall and seed. In paclobutrazol-treated plants the siliquae were darker green, and during active phases of growth both siliqua wall and seed exhibited higher total chlorophyll (Chl) content, decreased chl a/b ratios, greater hill reaction activity of chloroplasts and increased activities of -amylase, -amylase and invertase than controls. Paclobutrazol enhanced the levels of total soluble sugars, starch, protein and free amino acids in mature seeds. The seed oil content increased by 2 to 3 per cent with a treatment of 10 g mL^–1 pacolobutrazol.     

Genetic analyses of agronomic and seed quality traits of synthetic oilseedBrassica napus produced from interspecific hybridization ofB. campestris andB. oleracea

The heritability, the number of segregating genes and the type of gene interaction of nine agronomic traits were analysed based on F₂ populations of synthetic oilseedBrassica napus produced from interspecific hybridization ofB. campestris andB. oleracea through ovary culture. The nine traits—plant height, stem width, number of branches, length of main raceme, number of pods per plant, number of seeds per pod, length of pod, seed weight per plant and 1000-seed weight—had heritabilities of 0.927, 0.215, 0.172, 0.381, 0.360, 0.972, 0.952, 0.516 and 0.987 respectively, while the mean numbers of controlling genes for these characters were 7.4, 10.4, 9.9, 12.9, 11.5, 21.7, 20.5, 19.8 and 6.4 respectively. According to estimated coefficients of skewness and kurtosis of the traits tested, no significant gene interaction was found for plant height, stem width, number of branches, length of main raceme, number of seeds per pod and 1000-seed weight. Seed yield per plant is an important target for oilseed production. In partial correlation analysis, number of pods per plant, number of seeds per pod and 1000-seed weight were positively correlated with seed yield per plant. On the other hand, length of pod was negatively correlated (r = -0.69) with seed yield per plant. Other agronomic characters had no significant correlation to seed yield per plant. In this experiment, the linear regressions of seed yield per plant and other agronomic traits were also analysed. The linear regression equation wasy = 0.074x₈ + 1.819x₉ + 6.72x₁₂ -60.78 (R ² = 0.993), wherex ₈, x₉ and x₁₂ represent number of pods per plant, number of seeds per pod and 1000-seed weight respectively. The experiment also showed that erucic acid and oil contents of seeds from F₂ plants were lower than those of their maternal parents. However, glucosinolate content was higher than that of the maternal plants. As for protein content, similar results were found in the F₂ plants and their maternal parents. It was shown that the four quality traits, i.e. erucic acid, glucosinolate, oil content, and protein content, had heritability values of 0.614, 0.405, 0.153 and 0.680 respectively.     

Induction of fertile male flowers in genetically female Cannabis sativa plants by silver nitrate and silver thiosulphate anionic complex

Summary Apical application of silver nitrate (AgNO₃; 50 and 100 g per plant) and silver thiosulphate anionic complex (Ag(S₂O₃) ₂ ^3– ; STS; 25, 50 and 100 g per plant) to female plants of Cannabis sativa induced the formation of reduced male, intersexual and fully altered male flowers on the newly formed primary lateral branches (PLBs); 10 g per plant of AgNO₃ was ineffective and 150 g treatment proved inhibitory. A maximum number of fully altered male flowers were formed in response to 100 g STS. The induced male flowers produced pollen grains that germinated on stigmas and effected seed set. Silver ion applied as STS was more effective than AgNO₃ in inducing flowers of altered sex. The induction of male flowers on female plants demonstrated in this work is useful for producing seeds that give rise to only female plants. This technique is also useful for maintaining gynoecious lines.     

Morphological development of normal and phyllody expressing Rosa hybrida cv. Motrea flowers

A large number of soybean (Glycine max L. Merr.)flowers and young pods abscise rather than develop into mature pods. Flower andpod drop or abortion accounts for the majority of total reproductive abscissionand influences potential soybean yield. The objectives of this study were todetermine the patterns of flower, pod and seed development under treatmentswiththe growth regulators, 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and6-benzylaminopurine (BAP), applied at the early reproductive stages, and toexamine the association of reproductive abscission with growth characteristicsand agronomic traits, including seed yield and seed weight. Small seeded [cvPungsan (11.1±0.4 g100-seed^–1)] and large seeded [cv Manlee(21.0±0.5 g 100-seed^–1)]genotypes were separately planted in the greenhouse and field, and treated witheither 2,4-DP or BAP. 2,4-DP (a synthetic auxin) and BAP (a syntheticcytokinin)were each applied at three concentrations (i.e. high, intermediate or low):0.12mM, 0.08 mM, 0.04 mM, and 1.5mM, 1 mM, 0.5 mM respectively. High andlow concentrations were employed for greenhouse experiments to examine thenumber of flowers per plant in pots. With the exception of low BAP (0.5mM) treatment in Pungsan, all treatments increased total podnumberwith various numbers of seeds per pod. Low 2,4-DP (0.04 mM) inbothgenotypes or BAP (0.5 mM) in Manlee significantly reduced flowerabortion and delayed abscission of pods in both genotypes, resulting inincreased pod setting rates. Under field conditions using intermediateconcentrations, 1 mM BAP significantly increased 100-seed weightto22.3 g at R1 in Manlee and 11.9 g at R3 in Pungsan.BAP (1 mM) at R3 in Pungsan significantly improved seed yield(40.1g plant^–1). Maturity was not significantlyaffected by either application in Manlee, but was significantly affected by BAPin Pungsan. In Pungsan, 2,4-DP increased pod number, plant height and nodenumber, but decreased 100-seed weight in Pungsan treated at R1, causing nosignificant change of seed yield. This study suggested that exogenousregulatorssignificantly influenced reproductive and growth characteristics, andconsequently seed yield, but increase of pod number was not always beneficialfor seed yield.     

Ecological correlates of seed mass variation in Phoradendron juniperinum,a xylem-tapping mistletoe

Summary We investigated several ecological correlates of seed mass variation in the hemiparasitic, xylemtapping mistletoe, Phoradendron juniperinum. Mean seed mass varied two-fold among plants between the ages of 4 and 14 years old and was positively correlated with parental plant age. Both the standard deviation and the coefficient of variation in mean seed mass decreased with increasing plant age demonstrating that, on average, younger plants produced seed with more variable mass. Nitrogen concentrations (mg nitrogen per gram of seed) of both the seed and fruit (pericarp) were not correlated with mass or the age of the parent plant from which the seed was taken. However, the nitrogen content per seed (mg nitrogen per seed) was positively correlated with the mean seed dry mass and the age of the seed parent, suggesting that the carbon to nitrogen ratio of individual seeds remained relatively constant as seed mass increased and plants grew older. Seed germination ranged between 20% and 86% and was positively correlated with mass and parental plant age. Heavier seeds (seeds from older plants) also had the highest root radicle growth rates. Furthermore, the final root radicle length after 76 d of growth was positively correlated with seed dry mass. When grown on a medium containing an extract prepared from the host plant foliage, all seeds showed lower germination, grew more slowly and had shorter overall root radicles, but had significantly greater development of the haustorial disks (the holdfast which forms the host-parasite junction in Phoradendron) than seeds grown on a control medium. Our results suggest that, on average, seeds of greater mass produced by older plants have a greater total resource pool per propagule (fruit + seed). This resource pool may be important in conferring a greater potential for dispersal (fruit), survival, colonization, and establishment.     

Growth and development of soyabean cv. TK5 as affected by tropical daylengths, day/night temperatures and nitrogen nutrition

Two experiments were done in Saxcil growth cabinets in order to investigate the effects of climatic factors and nitrogen nutrition on the growth, reproductive development and seed yield of soyabean cv. TK5. In the first, plants were grown to maturity in eight environments comprising all combinations of two short daylengths (11 h 40 min and 13 h 20 min), two day (27 and 33^oC) and two night (19 and 24^oC) temperatures. In the second, day temperature was kept at 33^oC but the night temperature was varied (19 and 24^oC) as was the mineral nitrogen supply (20 and 197 ppm N) to plants which were either inoculated or not with an effective single strain of Rhizobium. Taller, more branched, later flowering plants were produced in the longer daylength but seed yield was hardly affected because the components of yield did not all respond similarly. In the higher day temperature treatments seed yield per plant was reduced by half because all yield components were adversely affected - pods per plant by 34 %, mean seed dry weight by 24 % and seeds per pod just slightly. There was a marked effect of the higher night temperature which promoted early vegetative growth, induced early flowering and although the number of pods per plant was, overall, reduced by 48 %, seed yield per plant was little affected as mean seed dry weight was increased by 37 % and the number of seeds per pod was also increased slightly. Prior to flowering, nodulated plants obtained about two thirds of their total nitrogen requirement via direct uptake and one third through the symbiotic system. Vegetative dry weight and plant nitrogen content were increased by the higher mineral nitrogen level and, although height was slightly diminished, more branches were produced. Seed yield, however, was only slightly increased. These experiments have shown that night temperature is an environmental factor of major importance for the growth of this soyabean cultivar. They have provided, also, a more rational basis for interpreting seasonal variations in growth and seed yield of soyabean in the tropics where, clearly, day and night temperature effects can override those of daylength and nitrogen nutrition.     

Constitutive expression of pea Lhcb 1–2 in tobacco affects plant development, morphology and photosynthetic capacity

Lhcb1–2 from pea was constitutively expressed in transgenic tobacco plants and assessed for functional impact. The successful assembly of the encoded proteins into LHCII trimers was confirmed by electrospray tandem mass spectrometry. Constitutive production of LHCb1–2 led to increased number of thylakoid membranes per chloroplast, increased grana stacking, higher chloroplast numbers per palisade cell and increased photosynthetic capacity at low irradiance, both on a chlorophyll and leaf area basis. The transgenic plants also displayed increased cell volume, larger leaves, higher leaf number per plant at flowering, increased biomass and increased seed weight, when grown under low irradiance levels. Under high irradiance, both transgenic and wild type plants displayed similar photosynthetic rates when tested at 25°C; however, the non-photochemical quenching (NPQ) and qE values increased in the transgenic plants. The exposure of transgenic plants to a photoinhibitory treatment (4°C for 4h, under continuous illumination) resulted in more detrimental impairment of photosynthesis, since recovery was slower than the non-transgenic plants. These data indicate that constitutive expression of additional Lhcb1–2 transgenes led to a series of changes at all levels of the plant (cellular, leaf and whole organism), and a delay in flowering and senescence. The additional production of the pea protein appears to be accommodated by increasing cellular structures such as the number of thylakoids per chloroplast, organelle volume, organelles per cell, and leaf expansion. The presence of the trimeric pea protein in the tobacco LHCII, however, caused a possible change in the organization of the associated super-complex, that in turn limited photosynthesis at low temperature.     

Physiological Effects of Plant Hormones in Cotton Under Drought

Effects of plant hormones indole-3-yl-acetic acid (IAA), gibberellic acid (GA), benzylaminopurine (BAP), abscisic acid (ABA) and ethrel (ETH) in 5 M concentration on gas exchange, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO, EC 4.1.1.39) activity, pigment content and yield in cotton (Gossypium hirsutum L. cv. H-777) under drought were studied. At reproductive stage (55 – 60 d after sowing) these hormones were sprayed on shoots one day prior to stress imposition by withholding irrigation. The soil moisture of control plants was kept at field capacity. Net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (E), carboxylation efficiency (CE), water use efficiency (WUE), RuBPCO activity, boll number per plant, seed number per plant and lint mass per plant significantly decreased at drought while chlorophyll (Chl) b content and flower number per plant increased. ABA and ETH significantly reduced gas exchange parameters, Chl a and Chl b content. Detrimental drought effect on P_N, g_s, E, CE, RuBPCO and lint mass per plant was significantly alleviated by BAP and also its effect on seed number and lint mass per plant was significantly alleviated with the ABA treatment.     

Effects of aluminium and pH on growth and potassium uptake by three ectomycorrhizal fungi in liquid culture

Clonal plants of white clover (Trifolium repens L.) were grown in a controlled environment with either low or high rates of applied nitrate-N (providing, notionally, insufficient or sufficient N for unrestricted growth), or in the absence of applied N. Plants receiving no nitrate-N were inoculated with Rhizobia and fixed their own N₂. All plants were maintained with a maximum of three fully unfolded leaves per apex (lenient defoliation) until day 68 when half of the plants were severely defoliated. The export and translocation of carbohydrates from the first fully unfolded main stolon leaf was measured three days later using ¹⁴C.Reduced carbon translocation to stolon tissue and roots, and increased translocation to young branches, occurred following severe defoliation in all three nitrogen treatments. However, N-deficient plants showed large reductions in total export of carbohydrates (44 vs. 17% of ¹⁴C assimilated for lenient vs. severe defoliation) whereas N-sufficient plants (either receiving nitrate-N or fixing their own N₂) showed small increases in total export (means of 54% vs. 62% in the respective defoliation treatments). Furthermore, carbohydrate translocation to old branches ceased altogether in severely defoliated, N-deficient plants, but increased in severely defoliated, N-sufficient plants, illustrating that plant responses to multiple-factor stresses may differ greatly from those seen as the result of single-factor stresses. Interactions between nitrogen nutrition and defoliation in total carbohydrate export, and in carbohydrate supply to old branches, could have serious negative effects on the short-term C economy and physiological integration, and hence on the adaptability, of clonal plants growing with a mineral deficiency in the presence of grazing animals.     

Symbiotic specialization and the potential for genotypic coexistence in a plant-bacterial mutualism

Genotypes of the annual legume Amphicarpaea bracteata vary in their degree of specialization toward different nitrogen-fixing bacteria. Plants of lineages Ib and II are specialized for mutualism with a limited group of bacterial genotypes. Lineage Ia plants are symbiotic generalists, interacting with all bacteria associated with specialist (Ib and II) plants, and also with a distinct class of bacteria that only fix nitrogen with lineage Ia plants. The relative performance of generalist and specialist plant lineages was measured in four symbiotic environments: (1) in the absence of nitrogen-fixing bacteria, (2) with bacteria with broad host ranges, (3) with bacteria specialized on lineage Ia hosts, and (4) with a mixture of the bacteria with broad and narrow host ranges. In the presence of bacteria with broad host ranges, the relative performance of different plant lineages was inconsistent among experimental replicates. However, lineage Ia plants had nearly 3 times higher total biomass and 6 times higher seed biomass than lineage Ib or II plants when grown with bacteria specialized on Ia hosts. When exposed to a mixture of bacteria with broad and narrow host ranges, generalist plants had 72% higher total biomass and >100% higher seed biomass than specialist plants. These results imply that in diverse natural populations, where all plants have a choice of symbiotic partners, mutualistic interactions are likely to foster competitive exclusion rather than stable coexistence of different plant lineages.     

Enhanced yield of tomato in response to 2-(3,4-dichlorophenoxy)triethylamine (DCPTA)

Application of the bioregulator, 2-(3,4-dichlorophenoxy)triethylamine (DCPTA) to tomato (Lycopersicon esculentum Mill. cv. Pixie) significantly increased the vegetative growth and fruit-yield productivities of mature plants. Compared with controls, application of 30 M (10 ppm) DCPTA as a pre-germination seed treatment increased the mean relative growth rates of leaves, stems, and roots, 37%, 16%, and 20%, respectively, during exponential growth. At fruit harvest, the dry weights of leaves, stems, and roots, and the harvestable yield of 30 M DCPTA-treated plants were doubled when compared with controls. Increases in both the total fruit number per plant and the size of individual fruits contributed to the improved yield of 30 M DCPTA-treated plants. The total soluble solids contents of mature fruits harvested from 30 M DCPTA-treated plants were increased 24%, and the lycopene and beta-carotene contents were doubled as compared with controls. These results indicate that DCPTA treatment does not adversely affect the balanced partitioning of photoassimilate to vegetative and reproductive sinks in tomato.     

Growth responses of rice seedlings to triacontanol in light and dark

Triacontanol, a 30-carbon primary alcohol, applied in nutrient culture solutions to rice (Oryza sativa L.) seedlings at 2.3×10^-8 M (10 g/l), caused an increase in dry weight and leaf area of the whole plants. The response could be observed as early as 3 h of treatment. It was observed at relatively high and low light intensities as well as in the dark where control plants lost but triacontanol-treated plants gained in dry weight. The dry weight gain in the dark was, however, eliminated by removing CO₂ from the atmosphere. Triacontanol-treated plants also increased their content of Kjeldahl-N and contained 30% more total N per plant than controls after 6 h in the dark.     

Abaxial and Adaxial Stomatal Density, Stomatal Conductances and Water Status of Bean Primary Leaves as Affected by Paclobutrazol

The plant growth retardant, paclobutrazol at 8.5 or 17.0 μM concentrations effectively inhibited the stem elongation and primary leaf expansion of bean seedlings. Although the retardant reduced the relative water content in well-watered plants, the water and pressure potentials remained high in the primary leaves. K⁺, Na⁺, Mg²⁺ and Ca²⁺ contents in the primary leaves of the paclobutrazol-treated plants were not significantly different from those in the control. The stomatal density increased on both surfaces but the length of guard cells was not reduced significantly on the adaxial epidermes of the paclobutrazol-treated primary leaves. The inhibitory effect of paclobutrazol on the abaxial stomatal conductances became more pronounced with time during the light period but the adaxial surfaces displayed similar or slightly higher conductances than those of the control. The transpiration rate on a unit area basis did not change significantly or increased in the treated leaves thus the reduced water loss of paclobutrazol-treated plants was due to the reduced leaf area. Stomatal conductances of the adaxial surfaces responded more intensively to exogenous abscisic acid and the total leaf conductance decreased faster with increasing ABA concentration in the control than in the paclobutrazol-treated leaves. Paclobutrazol, an effective inhibitor of phytosterol biosynthesis, not only amplified the stomatal differentiation but increased the differences between the adaxial and abaxial stomatal conductances of the primary leaves.     

Effect of exogenous plant growth regulators on in vitro seed growth,embryo development,and haploid production in a cross between H. vulgare (L.) and H. bulbosum (L.)

Exogenous plant growth regulators are known to increase the efficiency of interspecific and intergeneric crosses. In vitro floret culture provides a defined system for assessing the importance of various plant growth regulators on the determinants of haploid production efficiency (seed set, embryos per seeds, and plants per embryos) in Hordeum vulgare × Hordeum bulbosum crosses. The individual and combined effects of three plant growth regulators (2,4-D, GA₃ and kinetin) on in vitro seed growth, embryo development and haploid production efficiency were tested in floret culture of the cross H. vulgare, cultivar Klages × H. bulbosum. All treatments, except kinetin alone, produced larger seeds and more embryos/100 seeds than the control (no plant growth regulator). 2,4-D alone was superior to GA₃ alone in haploid production efficiency (70.6 vs. 51.5) as measured by the number of plants regenerated/100 florets pollinated. Although kinetin +2,4-D+GA₃ produced the largest seeds and embryos, no advantage over 2,4-D alone was observed in haploid production efficiency. 2,4-D alone or kinetin +2,4-D are recommended for the purpose of barley haploid production in floret culture using the bulbosum method.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid     

Genotypic variation in the effect of salinity on fertility in rice

The effect of salinity on the reproductive physiology of five rice genotypes (IR54, IR26, IR2153-26-3-5-2, IR15324-117-3-2-2 and BR6), was investigated by treatment from panicle initiation with sodium concentrations of 20, 35 or 50 mol m^-3 in an artificial seawater. In an experiment conducted in a glasshouse, plant height and dry weight were little affected by the treatments. There was, however, genotypic variation in the extent of the sodium accumulation, with IR15324-117-3-2-2 containing the highest and IR2153-26-3-5-2 the lowest concentrations: sodium concentrations were higher in older than younger leaves.Salinity delayed flowering, reduced the number of productive tillers, the number of fertile florest per panicle, the weight per grain and the grain yield: effects on grain yield were very much more severe than on vegetative growth. Panicle length was also reduced as was the number of primary branches in a panicle: again there was genotypic variation in the response of these characters to salinity, with the number of branches in IR2153-26-3-5-2 being particularly sensitive.The concentration of sodium increased in the pollen, stigmas, lemmas and paleas with each increment of external salinity. The highest concentrations of sodium in pollen and stigmas was recorded in IR54 and IR15324-117-3-2-2. Pollen viability, whether tested with the tetrazolium salt thiazolyl blue (3-{4,5-dimethylthiazolyl-2}-2,5-diphenyl monotetrazolium bromide or MTT), germination on stigmas, growth through the stylar tissue or F₁ seed set, was reduced particularly in those genotypes accumulating most sodium. At all three salt levels, a genotype which accumulated more Na in its pollen produced less-viable pollen than those with less Na in their pollen. Since the amount of Na in the pollen was highly correlated with the Na in the flag leaf, assessment of flag leaf Na should prove a useful indicator of the likely pollen viability. Stigmatic receptivity was also reduced, when estimated either from germination of viable pollen on stigmas of salt-grown plants, its growth through the stylar tissue or F₁ seed set. The reduction of seed set in crosses suggested that the overall consequences of salinity are dominated by effects on panicle development, stigmas and grain filling rather than on pollen.Analysis of the data suggests that genotypic variation exists in the extent to which salinity affects aspects of the plants reproductive physiology and development: this variation might be used in attempts to enhance the resistance of rice to salinity.     

Inhibition of stem growth and gibberellin production in Agrostemma githago L. by the growth retardant tetcyclacis

The effects of the new growth retardant tetcyclacis (TCY) on stem growth and endogenous gibberellin (GA) levels were investigated in the long-day rosette plant Agrostemma githago. Application of TCY (10 ml of a 5·10^-5M solution daily) to the soil suppressed stem elongation in Agrostemma grown under long-day conditions. A total of 10 g GA₁ (1 g applied on alternate days) per plant overcame the growth retardation caused by TCY.Control plants and plants treated with TCY were analyzed for endogenous GAs after exposure to nine long days. The acidic extracts were fractionated by high-performance liquid chromatography. Part of each fraction was tested in the d-5 maize bioassay, while the remainder was analyzed by combined gas chromatography-selected ion monitoring. The bioassay results indicated that the GA content of plants treated with TCY was much lower than that of untreated plants. The data obtained by gas chromatography-selected ion monitoring confirmed that the levels of seven GAs present in Agrostemma were much reduced in TCY-treated plants when compared with the levels in control plants: GA₅₃ (13%), GA₄₄ (0%), GA₁₉ (1%), GA₁₇ (33%), GA₂₀ (15%), GA₁ (4%), and epi-GA₁ (13%). These results provide evidence that TCY inhibits stem growth in Agrostemma by blocking GA biosynthesis and thus lowering the levels of endogenous GAs.Abbreviations AMO-1618 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride - GA(s) gibberellin(s) - HPLC high-performance liquid chromatography - TCY Tetcyclacis (5-[4-chlorophenyl]-3,4,5,9,10-pentaaza-tetracyclo-5,4,1,0^2,6,0^8,11-dodeca-3,9-diene)     

Some effects of environmental stress on seed yield of cowpea (Vigna unguiculata (L.) walp.) cv. Prima

Summary Separate experiments examined nodulation and seed yield of cowpea cv. Prima after (a) changes in the level of combined nitrogen from 25 to 0 or 60 ppm N, (b) cycles of wilting and rehydration, and (c) shading to ca 50% full daylight. Plants were grown in the simulated tropical environment of a plastics bubble house and experienced these changes over the growth stages: emergence to first flower, first flower to mid pod-fill or mid pod-fill to maturity.Seed yields of nodulated plants were unaffected by combined nitrogen supply and almost double those of non-nodulated plants (100 g cf 56 g per plant)-due mainly to increases in pod number per plant and mean seed weight. Reducing the nitrogen level from 25 to 0 ppm N, especially between mid pod-fill and maturity, reduced seed yields of non-nodulated plants to 36 g per plant. At the first flowering stage, plants grown without combined nitrogen had nitrogenase activities less than 10% of those supplied with 25 ppm N; 60 ppm N at any stage of development more than halved nitrogenase activity when compared with plants supplied with 25 ppm.Repeated wilting prior to flowering markedly reduced seed yields compared with the unstressed controls (41 g cf 76 g per plant)-mainly by decreasing subsequent pod production. Nodule weight and nitrogenase activity per plant were also much reduced. Wilting after flowering did not reduce yield, and nitrogenase activity was less affected.Shading throughout, or from first flower onwards, reduced seed yield by about 25% because fewer pods were produced. All shading treatments significantly increased mean seed weight compared with unshaded controls (116–121 mg cf 105 mg).One of a series of papers describing work undertaken in a collaborative project with the International Institute of Tropical Agriculture, Nigeria, sponsored by the U.K. Ministry of Overseas Development.Soil Microbiology Department, Rothamsted Experimental Station, Harpenden, Herts.Soil Microbiology Department, Rothamsted Experimental Station, Harpenden, Herts.     

Varying phosphorus supply and development,growth and seed yield in narrow-leafed lupin

Narrow-leafed lupin (Lupinus angustifolius L.) is usually grown in sandy, acidic and phosphorus (P) deficient soil with low yield and variable harvest index. This study aimed to examine the effects of varying P supply on lupin growth, seed yield and harvest index. Non-abscission plants (cv. Danja) were grown in Lancelin sand at seven rates of P supply (5, 10, 15, 20, 25, 30 or 40 mg kg^–1) in a naturally-lit glasshouse. The rate of leaf emergence, flowering time and flower number were decreased or delayed by low P supply (5, 10 or 15 mg kg^–1), with no differences at P rates higher than 20 mg kg^–1. High P supply (25, 30 or 40 mg kg^–1) increased plant seed yield and harvest index largely by increasing the number of pods and consequently yield on the lateral branches, but had less effect on the number of seeds per pod and seed size. Seed yield and seed P concentration continued to increase up to 40 mg P kg^–1but harvest index plateaued at 25 mg P kg^–1, indicating that low P supply decreased reproductive growth more than vegetative growth in narrow-leafed lupin.     

The use of antimicrotubule herbicides for the production of doubled haploid plants from anther-derived maize callus

Summary Four antimicrotubule herbicides, amiprophosmethyl (APM), pronamide, oryzalin, and trifluralin, were evaluated for their ability to induce chromosome doubling in anther-derived, haploid maize callus. Effects of various herbicide treatments on the growth and regenerative capacity of callus along with the ploidy and seed set of regenerated plants were determined. Flow cytometric analysis was also used to measure changes in ploidy levels of callus cells following treatments. More than 50% of the cells were doubled in chromosome number after the haploid callus was treated with 5 or 10 M APM or 10 M pronamide for 3 days. A similar proportion of plants regenerated from the treated callus produced seed upon self-pollination. APM and pronamide did not inhibit callus growth at these concentrations and the treated callus retained a high plant regeneration capacity. Oryzalin very effectively induced chromosome doubling, but severely inhibited the growth of regenerable callus and plant regeneration. Trifluralin induced chromosome doubling in a small proportion of cells at lower concentrations (0.5 and 1 M), however, at a higher concentration (5 M) it inhibited callus growth and plant regeneration. The results indicate that APM and pronamide may be useful agents for inducing chromosome doubling of anther-derived maize haploid callus at very low concentrations.     

Nutrient transport between ryegrass plants differeing in nutrient status

Summary It is known that nitrogen and phosphorus can be transferred from one living plant to another, but it is not known whether the amounts transferred are large enough to influence the growth of the species in the field. Two Lolium perenne plants were grown per pot of unfertilized soil. During 25 weeks one plant (the donor) in each pot was fed nutrients through leaves; donors in control pots received only water. The receiver plants which shared a pot with the nutrient-fed donors increased significantly, compared with the controls, in leaf number and concentration of phosphorus, though not in concentration of nitrogen, potassium, calcium or magnesium. The rate of phosphorus transfer agreed well with previous results using ³²P. The results are compared with rates of phosphorus uptake in the field. It is concluded that nutrient transfer could have an influence on the balance between coexisting species in the field, but probably the influence will be small.