Percentage Of Florets Research Articles

How panicle angle and panicle position in the canopy determine pollination and seed set in rice (Oryza sativa L.)

ABSTRACT We examined the effect of panicle position relative to canopy and of panicle angle on pollination and floret sterility in rice at anthesis in a paddy field. We set panicles of pot-grown rice at the flowering stage either upright (0°) or inclined (30°), either above or at canopy height (Experiment 1) and either beneath or at canopy height (Experiment 2), in three replications each. In Experiment 1 and Experiment 2, panicle inclination at 30° increased the percentage of florets with <20 total pollen grains on the stigma (TP20) by 21% and 27%, increased the percentage of florets with <10 germinated pollen grains on the stigma (GP10) by 21% and 30%, and increased floret sterility by 10% and 26%, respectively. Floret sterility was correlated with GP10 in all trials. GP10 was correlated with TP20. The effect of position on floret sterility was not significant. We conclude that panicle inclination at 30° significantly increased floret sterility even under the canopy condition. Uprightness of panicles should be an important objective in rice breeding and production. Abbreviations TP20, percentage of florets with <20 total pollen grains on the stigma; GP10, percentage of florets with <10 germinated pollen grains on the stigma.

Dependence of pollination and fertilization in rice (Oryza sativa L.) on floret height within the canopy

We examined changes in rice (Oryza sativa L.) floret sterility and pollination as a function of vertical position of florets in the canopy at anthesis in paddy fields to clarify the ideal panicle height. Flowering pot-grown rice plants were placed in the rice canopy at different heights to position their florets at different depths below the canopy surface. The percentage of floret sterility was approximated as Y = 0.000335 X12 + 0.0296 X1 – 0.0451 X2 + 0.0152 X1X2 – 0.0468 (R2 = 0.921), where Y is the logit-transformed floret sterility (%), X1 is floret depth at anthesis (cm), and X2 is wind speed above the canopy (m s–1). The percentage of florets with fewer than 20 pollen grains on the stigma after flowering was approximated well by Y = 0.000554 X12 – 0.235 X22 + 0.5346 (R2 = 0.892), where Y is the logit-transformed percentage. The floret sterility (%) was correlated with the percentage of florets with <10 germinated pollen grains and with the percentage with <20 total pollen grains. Thus, there exists an optimal flowering depth and an ideal panicle position with respect to the canopy surface that stabilizes pollination and fertilization, and the optimal position for fertilization deepens with increasing wind strength.

Panicle inclination influences pollination stability of rice (Oryza sativa L.)

ABSTRACTRice pollination occurs when pollen grains fall by gravity from the anther onto the stigma and has been thought to be assured under suitable conditions. However, the position of the stigma relative to the anther pores may affect pollination. The inclination of panicle, that is quite usual in agricultural scene, may change the relative position of anther and stigma. We investigated the effect of panicle inclination on pollination stability. Pots of rice at flowering stage were tilted at one of the four inclinations (0° = control, 15°, 30°, and 45°). We assessed pollination (numbers of total and germinated pollen grains on the stigma) and morphology of dehisced anthers. Inclination significantly affected the number of total and germinated pollen grains on the stigma: as it increased from 0° to 45°, the percentage of florets with <20 total pollen grains on the stigma (TP20) increased from 36.6% to 59.9%, and that of florets with <10 germinated pollen grains on the stigma (GP10) increased from 26.6% to 58.9%. Both an increase in TP20 and a decrease in the rate of pollen germination were major causes of the increase in GP10. Inclination did not affect anther morphology. A panicle inclination of ≥30°could greatly reduce rice production because rice fertilization requires >10 germinated pollen grains on the stigma. Uprightness of the panicle at flowering should be an important objective in rice breeding and production.Abbreviations: TP20: percentage of florets with <20 total pollen grains on the stigma; GP10: percentage of florets with <10 germinated pollen grains on the stigma

Effects of Various Phytohormones On Haploid Wheat Production in Wheat x Maize Crosses

The Effects of Phytohormones On The Production of Haploid Wheat Were Examined in The intergeneric Crosses Between Japanese Wheat Cultivar (Triticum Aestivum Cv. Zenkojikomugi) and Maize (ZEA MAYS Cv. Pioneer P80 Lisa). The Detached Wheat Spikes Pollinated With Maize Were Cultured in A Solution Containing Sucrose and Sulfurous Acid Supplemented With 2,4―Dichlorophenoxyacetic Acid (2,4―D), indole-Acetic Acid, Naphthalene Acetic Acid, Kinetin Or 6-Benzylaminopurine At 0, 0.1, 1, 10, 100 Or 1000 Mg L-1. Haploid Embryos Obtained Were Cultured On Agarose-Solidified B5 Medium. The Frequency of Plant Regeneration Was Significantly Affected Only By The Treatment With 100 Mg L-1 2,4―D. Thus, The Detached Spikes Were Cultured in The Medium Containing 2,4―D At 0, 25, 50, 75, 100, 125, 150, 175, 200 Or 400 Mg L-1. The Treatments With 50 Mg L-1 2,4―D increased The Embryo Size, But The Treatments With Above 75 Mg L-1 2,4―D inhibited The Development of The Embryo. The Percentage of Florets Developing into Haploid Plants Was increased By The Treatment With 100 Mg L-1 2,4―D. Therefore, The Concentration of 2,4―D in THe Spikes Treated With 2,4―D At 50, 100 and 150 Mg L-1 WERe Measured By Gas Chromatography. The Concentration of 2,4―D in THE Seed Was increased To 9.24 Ppm By The Treatment With 100 Mg L-1 2,4―D, A Further increase of 2,4―D Concentration in The Medium Having No Effect. On The Other Hand, The Concentration of 2,4―D in The Glumes and Rachis increased Up To 12.72 and 41.55 Ppm By The TreatmenT With 100 and 150 Mg L-1 2,4―D, Respectively. The Treatments With 2,4―D At A Concentration Higher Than 100 Mg L-1 inhibited Embryo Development. The Present Results Suggested That 2,4―D At The Concentrations From 50 To 100 Mg L-1 Would Be Optimum For Haploid Wheat Production Using Maize.

Effect of 2,4-Dichlorophenoxyacetic Acid on the Efficiency of Wheat Haploid Production by the Hordeum bulbosum Method

Intergeneric crosses between Japanese wheat cultivars (Triticum aestivum L. cv. Nishikazekomugi and Zenkojikomugi) and a tetraploid wild barley, Hordeum bulbosum L. were used to examine the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on the formation of wheat haploid embryo and its development into plantlets. The detached wheat spikes with florets pollinated with H. bulbosum were cultured for 14 days in a sucrose and sulfurous acid solution to which 2,4-D was added at the concentrations of 0, 25, 50, 75, 100, 125, 150, and 175 mg L−1. The percentages of florets with seeds set and with embryos formed were increased by increasing the concentration of 2,4-D up to 100 mg L−1. Fourteen days after pollination, embryos (haploid) were isolated from the seed and cultured on agarose-solidified B5 medium. Embryo size tended to decrease as the concentration of 2,4-D increased, but the larger embryos tended to have higher ability to develop into haploid plants. The percentage of florets from which haploid plantlets were developed by embryo culture was slightly increased by the treatment of the spikes with 25-100 mg L−1 2,4-D, but significantly reduced by 125-175 mg L−1 2,4-D. It is suggested that treatment with 2,4-D at 25 100 mg L−1 would be effective for haploid wheat production by of H. bulbosum method.

Correlation between Viability of Pollination and Length of Basal Dehiscence of the Theca in Rice undera Hot-and-Humid Condition

Anticipated global warming may increase the floret sterility of rice (Oryza sativa L.). For selection of genotypes tolerant to high temperatures during the flowering period, it is important to identify morphological traits associated with tolerance to temperature stress. This study investigated the relationship between the length of dehiscence at the basal part of thecae and the viability of pollination in 18 cultivars of rice subjected to a hot-and-humid condition (37/25 ˚C, day/night, >90% relative humidity) for three days at flowering. Control plants were left under the ambient conditions in a semi-cylindrical house covered with cheesecloth (30% shading; temperature range: 24-35 ˚C). The length of basal dehiscence of thecae and the number of pollen grains on the stigmata were examined with a light microscope after flowering. The length strongly correlated with the percentage of florets having more than 80 pollen grains on the stigmata under the ambient condition (r = 0.72, P < 0.001), and with the percentage of florets having more than 20 pollen grains on the stigmata under the hot condition (r = 0.93, P < 0.001). In other words, the length correlated with pollination viability or reliability under both conditions. In addition, basal dehiscence was shorter in the non-japonica-type cultivars than in many of the japonica-type cultivars under both conditions. We concluded that the low pollination viability in the non-japonica-type cultivars is associated with their small basal dehiscence on the thecae, and the length of basal dehiscence can be used as a selection marker of high temperature tolerance.

The Difference in Sterility due to High Temperatures during the Flowering Period among Japonica-Rice Varieties

SummaryThe objectives of this study are to compare the floret sterility induced by a high temperature given in the daytime during the flowering period among nine japonica rice varieties, and to clarify the mechanism of the high-temperature-induced sterility. Nine japonica rice varieties were subjected to 35.0, 37.5 or 40.0°C day- temperature conditions (1000-1600) for six consecutive days using sun-lit phytotrons, and the percentage of fertility, pollination and germinated pollen grains on the stigmas were examined. The temperature that caused 50% sterility varied with the variety, and a difference of approximately 3.0°C was observed between the most tolerant and susceptible varieties. Under the 37.5°C day-temperature condition, the percentage of florets with 10 or more germinated pollen grains was roughly coincident with the percent fertility, but under the 40° C day-temperature condition, it was higher than the percent fertility. Many of the florets with less than 10 germinated pollen grains had less than 20 total pollen grains on their stigmas under both temperature conditions. From these results, we concluded that sure pollination under high-temperature conditions is an important factor and that the high-temperature tolerance of the processes following pollen germination is also required for fertility under excessively high temperature conditions.

PATHWAYS OF BACKCROSSING ZINNIA ANGUSTIFOLIA × Z. ELEGANS INTERSPECIFIC HYBRIDS TO THE PARENTAL SPECIES

Allotetraploid Z. angustifolia × Z. elegans hybrids (2 n =46) were reciprocally backcrossed to Z. angustifolia (2 n = 22 or 44) and Z. elegans (2 n = 24 or 48). Pollen germination and pollen tube penetration of the stigmatic surface were observed for all 8 cross combinations. At 14 days after pollination, the percentage of florets with embryos ranged from 0 to 69%, and some hybrid embryos exhibited developmental abnormalities. Seed-propagated backcross (BC1) populations were generated with Z. angustifolia (2 n =44)as ♀ or ♂, and Z. elegans (2 n =48) as ♀ BC1 progeny from these 3 crosses demonstrated low to high levels of resistance to bacterial leaf and flower spot (incited by Xanthomonas campestris pv. zinniae) and high levels of resistance to powdery mildew (incited by Erysiphe cichoracearum). BC1 hybrids derived from crossing allotetraploid hybrids as ♀ and Z. elegans (2 n =48) lines have commercial potential as disease-resistant, flowering annuals.

Self-incompatibility of Zinnia angustifolia HBK (compositae)

Visible light and UV epifluorescence microscopy were used to assess self-incompatibility (SI) in Zinnia angustifolia clones. Pistils were fixed 24 h after pollination and stained either with aniline blue in lactophenol (visible light microscopy) or decolorized aniline blue (fluorescence microscopy). Percentage of florets with embryos 21 days following pollination (% embryo set) was used as a control. Embryo set following self- or incompatible cross-pollinations ranged from 0% to 9.9%, whereas compatible crosses yielded 55.5%–87.1% embryo set. Observations using visible light microscopy indicated pollen load and number of germinated grains were significantly higher for compatible compared to incompatible crosses, and both variables were positively correlated (r = 0.89–0.96) to % embryo set. Examinations with UV epifluorescence microscopy revealed pollen load was higher and little or no callose accumulated in stigmatic papillae following compatible crosses, whereas for incompatible crosses, pollen load was low and callose lenticules were deposited in stigmatic papillae; the correlation between pollen load and % embryo set was 0.89. The intensity of callose fluorescence of the pollen tube-papillae attachment sites was quantitatively measured via micro spectrofluorometry. Callose fluorescence intensity ranged from 47.9% to 62.6% for incompatible and from 6.4% to 9.9% for compatible crosses, and was negatively correlated (r= — 0.95) with % embryo set. Microscopal techniques permit rapid assessment of SI and may be used routinely when each observed or measured parameter is highly correlated to the incompatibility response.

The Impact of a Pathogen (Puccinia Lagenophorae) on Populations of Groundsel (Senecio Vulgaris) Overwintering in the Field: II. Reproduction

SUMMARY (1) Reproduction during the spring was studied in monocultures of groundsel (Senecio vulgaris L.) overwintered in the field. In the autumn, populations had been either inoculated with a fungal pathogen (Puccinia lagenophorae), which caused rust disease, or left as controls. The effects of rust infection were examined in relation to status within a hierarchical population (assessed by sub-classes based on shoot dry weights). (2) In control populations, the first capitulum buds were produced in late February. The onset of flowering became progressively delayed as status within the hierarchy declined. In all sub-classes of the population, rust infection during the previous autumn delayed flowering in the spring by 1-2 weeks. (3) The percentage of plants within a sub-class that were reproductive (bore buds or capitula) in March and April declined as status in the hierarchy decreased. In classes of comparable status, fewer plants flowered in inoculated than in control populations. (4) In April, sub-classes with low mean dry weights in both populations produced fewer buds and mature capitula. The number of florets per capitulum were also decreased in lower status classes. Rust inhibited all measured components of reproduction in all classes. (5) During May, many large control plants senesced and their reproductive output declined. Thus, most sub-classes of control populations produced a similar number of florets. In contrast, vegetative growth in inoculated populations continued and all measures of reproduction were far greater in the class of highest status than in any other. There was a seven-fold increase in the contribution of this class to floret production (70%) relative to its frequency in the original population. In control populations, there was no more than a two-fold difference between floret production and frequency in the parent population. (6) Infection resulted in no significant change in the percentage of florets that developed into seed or in the viability of seed. (7) Over the duration of this experiment, the potential seed production of control populations (calculated from capitulum production, florets per capitulum and percentage seed set) was >460 000 seeds m-2. Populations that had been rust-infected in the autumn potentially produced 183 000 seeds m-2, a reduction of >60% compared

Irrigation and Nitrogen Studies in s. 23 Ryegrass Grown for Seed: 1. Growth, Development, Seed Yield Components and Seed Yield

SUMMARYThe effects of irrigation and nitrogen on S. 23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1972 to 1974. Irrigation significantly increased seed yield by 16% in 1972 and 52% in 1974 but had no effect in the wet year of 1973. In 1972 maximum deficit reached 110 mm at the end of July and coincided with anthesis. Consequently the yield response was due to an increase in number of seeds per unit area and no other seed yield component was affected. In 1974 peak deficit also reached about 100 mm but started to build up rapidly very early in the season and had reached 80 mm by the time that the first ears emerged. Consequently the yield response was due to increases in number of fertile tillers, number of seeds per unit area and 1000-seed weight.Irrigation had no significant effect on number of florets or seeds, except in 1974 when percentage of florets which produced seed was increased by 2%.Irrigation had some effect on threshed straw yields, total dry matter, harvest index and total number of tillers but where this occurred the response was much smaller than that of seed yield which indicates that irrigation had greater effects on the reproductive development of the crop than on yield of dry matter and tillering patterns. Increasing the quantity of nitrogen from 0 to 80 kg/ha increased seed yields, all seed yield components except 1000-seed weight, threshed straw yields and total dry matter and number of tillers at most sampling dates. Increasing the quantity of nitrogen from 80 to 160 kg/ha had little further effect on the above components except in 1972 where seed yields were significantly decreased.In 1972 number of florets was increased and percentage of florets which produced seed decreased with increasing quantities of nitrogen.

Título en español.

Durante los años 1963 y 1964, en la Subestación de Isabela de la Estación Experimental Agrícola de la Universidad de Puerto Rico se llevaron a cabo unos estudios para determinar la producción de semilla de la planta leguminosa Tephrosia vogelii. Las mejores líneas produjeron de 450 a 500 kg. de semilla por hectárea, pero esto fue sólo una fracción de su capacidad de rendimiento. Un gran porcentaje de las flores no produjeron vainas. Esto se atribuyó, en parte, a la ausencia de los insectos polinizadores, pero también pudo haber sido ocasionado por factores ambientales y fisiológicos desconocidos. Los coeficientes de correlación fueron pequeños, pero significativos, e indicaron la tendencia de que las mejores productoras de semillas fueran las plantas de mayor altura y también las que florecieron más temprano. No hubo relación significativa alguna entre el contenido de rotenoides y la producción de semilla. Se sugiere establecer un programa de hibridación para aumentar simultáneamente el rendimiento de semilla y el contenido de rotenoides.

Lucerne investigation: II. Pollination and seed setting in lucerne strains

1. The differences between strains in respect of tripping, pollination, self- and cross-fertilization, the number of pods and seeds set under comparable conditions, and the influence of weather and insects on these aspects was investigated during 1953–5 at Cambridge. Early, mid-season and late strains of lucerne were included in the experiments.2. Early strains under natural conditions had a significantly higher percentage of florets tripped, and pods formed, than mid-season or late strains. The ease with which early strains tripped, and the likelihood that biological characters of their flowers were better adapted to environmental conditions, are possible reasons for their high percentage of pods set.3. Tripping is essential for seed setting; at least 98·5% of pods resulted from florets tripped by insects or automatically.4. There was little difference between strains in the percentage of self-fertilized florets, although in the early strains there was a slightly higher percentage, as well as a higher number of selffertilized plants. There was little difference between strains in the average number of seeds set per pod which was about 1·9 for artificial tripping and selfing and 1·5 for selfing under continuous cover. Under natural conditions, the estimated proportion of pods formed due to selfing was 20% in Eynsford and Du Puits, 12% in Provence and 16% in Grimm. The difference between strains in the percentage of pods formed by artificial crossing was small. The average number of seeds set per pod was 3·9 under natural conditions and 6·7 under artificial crossing for all strains.5. Sunshine and high temperature encouraged tripping while rainfall suppressed tripping and pod setting. When the effect of temperature and rainfall were eliminated, duration of sunshine was the most important factor influencing tripping. Some variations in tripping and pod setting were found among plants of all strains in different seasons.6. The population of wild bees was very low. Honeybees and other small insects caused some accidental tripping and crossing, especially in early strains.