Structural Changes of the Grain Associated with Black Region Formation in Pennisetum americanum

The structure and ontogeny of grains of Pennisetum americanumare described with particular reference to the black regionon the abgerminal surface of the grain. Darkly pigmented materialwas deposited in the cells of the chalazal pad at black regiondevelopment. This colour development was associated with thecrushing of the transfer cells of the basal endosperm by theembryo and the cessation of transfer of ¹⁴C-labelled assimilateinto the grain. It is proposed that the growth of the embryointo the basal endosperm transfer cells and the subsequent accumulationof the pigmented material are the mechanisms by which graingrowth is halted.     

New sources of dwarfing genes in pearl millet (Pennisetum americanum)

Summary Thirteen naturally occurring dwarf lines of pearl millet [Pennisetum americanum (L.) Leeke], identified from the world collection, varied for several morphological and agronomic characters. Extreme dwarfs were characterized by a tufted growth habit which could be distinguished from the time of germination, while the other dwarf lines could be distinguished only after anthesis. The F₁ hybrids between the tall and dwarf genotypes were tall, indicating that dwarfness is a recessive trait. In 10 out of the 13 crosses, the F₂ segregation ratio was three tall to one dwarf (31) suggesting that the dwarfness is controlled by a single recessive gene, while the height differences in 3 of the dwarfs (IP 8056, IP 8210 and IP 8214) were controlled by more than one gene as they showed continuous variation for plant height in F₂. When the remaining 10 single gene dwarfs were crossed to either d ₁ (Tift 238) or d ₂ (Tift 23 DB) dwarfs, only 2 crosses produced tall F₂ hybrids and they segregated for height in F₂ indicating that these 2 dwarfs are non-allelic to d ₁ and d ₂. Reciprocal crosses of these 2 dwarfs produced tall F₁ hybrids and showed a dihybrid segregation of 934 in F₂ indicating that the dwarfing genes of these 2 parents are non-allelic to each other. These non-allelic dwarfs were assigned the gene symbols d ₃ (IP 10401), and d ₄ (IP 10402).Submitted as J.A. No. 429 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Environmental Influences on Panicle Differentiation and Spikelet Number of Pennisetum americanum

Pearl millet (Pennisetum americanum (L.) Leeke) has a juvenilephase after which the time to panicle initiation is reducedby short daylengths. To understand more fully the mechanismunderlying temperature ? daylength interactions on panicle initiationand differentiation, plants were grown (a) at a range of constanttemperatures under a short daylength from sowing until afterpanicle differentiation and (b) at one temperature until 20d after emergence and then at a range of temperatures duringa 10 d exposure to short daylength. Temperature prior to panicle initiation determined the numberof leaves initiated on the main stem and the size of the apicaldome at the start of panicle initiation. The number of leaves,in turn, influenced the duration of the phase from panicle initiationto anthesis: this phase required a constant thermal time whenexpressed as day degrees per leaf. At anthesis, panicle lengthwas positively correlated with the number of leaves on the mainstem (and temperature) prior to panicle initiation. Changingthe temperature only during exposure to inductive daylengthsaffected the rate of growth of the apical dome so that panicledifferentiation began within 10 d at high temperature (30?C)whereas differentiation did not commence in 10 dat 21?C. Paniclesdeveloped normally if differentiation had commenced under inductivedaylengths whereas panicles were abnormal when plants were returnedto long daylengths after panicle initiation but before visibledifferentiation. Relative extension rates of the panicle during differentiationwere correlated positively with temperature. The results areconsistent with the hypothesis that panicle initiation dependson the apex attaining a critical size and that temperature,by determining the number of leaves initiated on the main stem,affects the size of the apical dome and thus the onset of panicleinitiation, the duration of paniclc differentiation and thenumber of spikelets differentiated. Key words: Pennisetum americanum, panicle differentiation, spikelet number     

Spontaneous chlorophyll mutants of Pennisetum americanum: Genetics and chlorophyll quantities

Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F₁'s (mutant x control green). In F₁'s of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F₁'s of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.     

Cytogenetics of a factor for syncyte formation and male sterility in Pennisetum americanum

Summary Male sterility in Pennisetum americanum (L.) Leeke, inbred line IP 482, was found to be inherited as a monofactorial recessive phenotype. Homozygosity for the gene designated ms 2, produced in addition to pollen abortion, plasmodial tapetum, plasmodial pollen mother cells, delayed and asynchronous meiotic development, desynapsis and blockage of meiosis. Plasmodial PMCs resulted from the fusion of PMCs at pachytene.     

Panicle Differentiation and Spikelet Number Related to Size of Panicle in Pennisetum americanum

The size of the developing panicle of pearl millet (Pennisetumamericanum (L.) Leeke) was studied during panicle differentiation(from panicle initiation to the completion of spikelet production)in plants grown in pots or in the field and supplied with varyinglevels of nitrogen. The duration of panicle differentiationrequired a constant thermal time (day degrees) under all nitrogensupplies. However, the rate of growth of the developing panicleduring this phase was retarded by low nitrogen supply. Duringpanicle differentiation, it appeared that the developing paniclehad to reach a critical size before developmental events suchas the initiation of spikelet primordia commenced; timing ofdevelopmental events was related to the size of the developingpanicle. The number of spikelets produced depended on the rate of growthof the differentiating panicle and the duration of the phaseof spikelet initiation (from appearance of the first spikeletprimordium to completion of spikelet differentiation). Low nitrogensupply reduced the number of spikelets produced, by retardingthe rate of growth of the differentiating panicle; this delayedthe time to initiation of spikelets and thereby reduced theduration of spikelet initiation. All spikelets (irrespectiveof nitrogen supply on the mainstem and on tillers) occupiedthe same area of panicle surface at the completion of differentiationof the panicle and at anthesis. Key words: Millet, Panicle differentiation, Spikelet number     

Trisomic categories in pearl millet (Pennisetum americanum (L.) Leeke)

Summary In pearl millet [Pennisetum americanum (L.) Leeke], in the open pollinated and crossed progenies of autotriploids, desynaptics and translocation heterozygotes, two primary trisomics, one each of secondary and tertiary trisomics, two primary trisomics with interchanges, two interchange secondary trisomics, and three interchange tertiary trisomics were located. These categories were determined on the basis of chromosomal associations formed at meiosis. In one other trisomic, its category, whether tertiary or interchange trisomy, could not be determined. Some of these categories, like the secondary trisomy and interchange tertiary trisomy, are reported for the first time.     

Light-Induced Chloroplast [alpha]-Amylase in Pearl Millet (Pennisetum americanum)

In pearl millet (Pennisetum americanum) seedlings light induces the appearance of a leaf [alpha]-amylase isozyme. The leaf [alpha]-amylase isozyme was present in enriched amounts in isolated chloroplast but it could not be detected in isolated etioplasts. The chloroplast [alpha]-amylase was present in both mesophyll and bundle-sheath chloroplasts. Preliminary characterization indicated that molecular properties of chloroplast [alpha]-amylase were like those of a typical [alpha]-amylase. The plastidic [alpha]-amylase had a molecular mass of 46 kD, pH optimum of 6.2, required Ca2+ for activity and thermostability, but lost activity in the presence of ethylenediaminetetracetate. Plastidic [alpha]-amylase activity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis could be renatured in situ by Triton X-100. Western blot analysis demonstrated that this protein was antigenically similar to a maize seed [alpha]-amylase. In vivo [35S]methionine labeling of bundle-sheath strands isolated from light-grown leaves followed by immunoprecipitation revealed that bundlesheath strands synthesized plastidic [alpha]-amylase de novo.     

Collection and evaluation of Pearl Millet (Pennisetum americanum) Germplasm from Ghana

An expedition to Ghana was undertaken during August 1981 to collect mainly the early-maturing pearl millet, Pennisetum americanum. The collection team travelled extensively in most of the pearl millet-growing areas of the eastern and northern provinces of Ghana. The mission was planned to coincide with harvesting so that early-maturing landraces could be obtained from farmers’ fields. Seed samples of late-maturing pearl millet were also obtained from local markets. Early-maturing pearl millet is traditionally intercropped with groundnut (Arachis hypogaea), sorghum (Sorghum bicolor) or late-maturing pearl millet. Pearl millet grain is used in several traditional food preparations: thick porridge called tô, a thin, fermented porridge calledkoko, and a deep-fried pancake calledmarsa. Landrace populations grown by the farmers were mixtures of several types. The material collected varied considerably for shapes, sizes and colors of spikes and grains. Of the 284 samples collected, 227 were grown in a uniform nursery at Patancheru: they flowered in 39–140 days, grew 120–315 cm tall, spikes were short (6–53 cm) and conical, grains were large, globular and gray with starchy endosperm. The samples belong to race globosum and serve as a good source of genes for earliness and large-grain size.     

Temporal Profiles of Proteins Responsive to Transient Ischemia

The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia.     

Enhanced plant regeneration in pearl millet (Pennisetum americanum) by ethylene inhibitors and cefotaxime

Cefotaxime, a cephalosporin antibiotic, and different ethylene inhibitors, such as silver nitrate, cobalt chloride, nickel chloride and O-acetyl salicylic acid, significantly delayed the loss of regeneration potential in embryogenic cultures of Pennisetum americanum. In the presence of these chemicals, ethylene content in the atmosphere of the culture vessel was less than that of the control. Cefotaxime, silver nitrate and O-acetyl salicyclic acid did not have any effect on callus growth based on fresh weight, while growth based on dry weight was enhanced by O-acetyl salicyclic acid.Abbreviations ASA O-acetyl salicylic acid - BA benzyladenine - CW coconut water - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - NAA -naphthaleneacetic acid - MS Murashige and Skoog     

Effect of Temperature During Various Growth Stages on Grain Development and Yield of Pennisetum americanum

In controlled temperature glasshouses plant morphology, gramdevelopment and yield of pearl millet (Pennisetum americanum)were markedly affected by temperature during three stages ofplant growth: vegetative, stem elongation, and grain development.High temperature (to 33/28 °C day/night) during all threegrowth stages lowered grain yields by reducing basal tillering,numbers of grains per inflorescence, and single grain weight.Low temperature (21/16 °C) during the vegetative stage increasedbasal tillering and, as a result, total grain yield per plant.However, low temperature during the stem elongation stage reducedspikelet fertility and influorescence length, and thereby reducedthe potential main shoot grain yield. Low temperature duringgrain development increased the grain filling period and grainyield. The rate of grain filling did not vary over the rangeof 21/16 to 33/28 °C. Although plant morphology and grainyield were markedly affected by pre-anthesis thermal environment,grain development was not. At all temperatures ethanol-solublecarbohydrates stored in the stem were depleted during earlygrain development.     

Uptake of Proteins by Plant Roots

The patterns of uptake of fluorescein-labelled lysozyme (Fl-lysozyme) by barley, maize, onion, tomato and vetch are similar as revealed by fluorescence microscopy. Penetration of the root cap and through the epidermis into the cortex increases with time of exposure and decreases with higher salt concentrations. In fact, one molar ethylammonium chloride can remove most of the absorbed protein from treated roots and the space observed to be stained by Fl-lysozyme in this manner can be visualized as “free space”. Results with sterile and non-sterile barley roots were indistinguishable. At low ionic strength, Fl-lysozyme can penetrate cells and complex with nucleoli. Such cell protoplasts appear “coagulated”. Uptake results with fluorescein per se were unlike those with protein. The uptake of a much larger molecule, ferritin, is confined to the epidermis and root cell walls. Localized, absorbed protein and root growth inhibition by basic proteins have yet to be related.     

Analysis of meiosis and non-random bivalent formation in desynaptic mutants of Pennisetum americanum (L.) Leeke

Meiotic behaviour of induced desynaptic mutants of Pennisetum americanum (L.) Leeke in general was described.The frequency distribution of bivalents in induced desynaptic mutants was compared with that expected on the basis of the binomial series. The deviation from the binomial distribution was tested as to its conformity with models based on intra-and intercellular differences in bivalent formation. It is suggested that in these desynaptic mutants of Pennisetum americanum bivalent formation is non-random, which is largely due to the result of intracellular differences in chromosome behaviour regarding their requirements for chiasma formation.     

Somatic Embryogenesis and Plant Regeneration from Suspension Cultures of Pearl Millet (Pennisetum americanum)

Immature embryos of Pennisetum americanum (pearl millet), culturedin the presence of 2,4-dichlorophenoxy acetic acid (2,4-D) produceda pale-yellow and compact callus tissue by proliferation ofthe scutellum. Teased pieces of the compact callus were placedin a liquid medium on a gyrotory shaker to establish suspensioncultures. The cultures were composed of large, elongated andhigly vacuolated cells, and a population of richly cytoplasmiccells. The latter, here termed embryogenic cells, containednumerous plastids with starch, and occurred in tight groupsof four or more cells, and occasionally as single cells. Structuresresembling various stages of embryogenic development were foundin the suspension cultures. When the cultures were plated ina 2,4-D-free agar medium containing abscisic acid, embryoidswith the typical organization of cereal embryos were produced.The embryoids ‘germinated’ in vitro to give riseto plantlets, which were successfully transferred to soil. Theregenerated plants showed the normal diploid chromosome numberof 14. Embryoids apparently arose from single embryogenic cells,either directly or after the formation of a proembryonal massof cells. embryogenesis, pearl millet, Pennisetum americanum, regeneration, suspension culture     

DNA and RNA Levels in Bundle Sheath and Mesophyll Cells of Pearl Millett (Pennisetum americanum)

The DNA content of bundle sheath cells and mesophyll protoplasts from the C₄ plant pearl millet (Pennisetum americanum, Tift 23DB) was determined by microspectrophotometry to be 1.8 to 2.3 and 3.2 to 4.0 picograms/nucleus, respectively. Measurement of RNA by ultraviolet spectroscopy indicated that bundle sheath cells contain twice as much RNA as mesophyll cells.     

植物基因光反应元件及其结合蛋白

本文介绍了植物基因的G-box、GT元件等光调控元件及其结合蛋白的类型、结构特点和相关研究进展。     

Effects of Grain Development and Thermal History on Grain Maturation and Seed Vigour of Pennisetum americanum

Studies were made of the viability and vigour of seeds of pearlmillet (Pennisetum americanum) harvested at different stagesof grain development and from different controlled-temperatureenvironments. Seed viability and vigour of the next generationwere dependent on the extent of grain development at harvest.Where grain had developed for only one-third of the potentialgrain-filling period before harvest, seed viability and vigourwere greatly reduced. Harvest at or after the middle of grain-fillingdid not reduce seed viability or vigour. The temperature atwhich the grains had developed did not affect seed viability,but grains that had developed at 21/16 °C (day/night) producedseedlings of greater height and dry weight than those from grainswhich had developed at higher temperatures.     

Effect of combined inoculation ofAzospirillum brasilense and vesicular-arbuscular mycorrhiza on pearl millet (Pennisetum americanum)

Summary Growth and phosphorus uptake of pearl millet (Pennisetum americanum) on an unsterile, phosphorus-deficient soil was improved by the seed inoculation withAzospirillum brasilense or soil inoculation with the vesicular-arbuscular mycorrhizal fungi (Acaulospora,Gigaspora margarita, Glomus fasciculatum). These microorganisms acted synergistically when added simultaneously and the response was significant withAzospirillum brasilense + Gigaspora margarita andAzospirillum brasilense + Glomus fasciculatum combinations over uninoculated control as far as the dry matter content of shoots, root biomass and phosphorus uptake of the millet was concerned.