Proportion Of Spikelets Research Articles

Heat stress effects on sexual reproductive processes of a threatened halophyte

Sexual reproduction, a critical life history process in plants, can be altered by heat stress derived from global warming. Sexual reproduction increases genetic diversity, and the ability of plants to respond to environmental changes and dispersal. The capacity for these responses is especially relevant as plants are exposed to rising environmental stress levels imposed by climate change. We investigated the influence of environmental factors that impose physiological stress that may affect the fruit set of Spartina maritima, the sole native African and European cordgrass species. To achieve our objective, we acquired locally recorded air temperatures and tidal amplitude projections. Within population sites, we measured sedimentary conditions (pH, redox potential and electrical conductivity), and the phenological stage of S. maritima inflorescences, spikelets with non-exserted stamens and caryopses produced throughout its 10-week flowering period. Fruit set decreased as flowering period advanced, and as air temperatures and the proportion of spikelets with non-exserted stamens increased. Fruit set decreased with increased sediment anoxia. The proportion of reabsorbed caryopses increased with high air temperatures during the female phase of the inflorescence, and with higher tidal amplitudes during the male phase. These environmental stress factors could terminate caryopsis development that had commenced. Our results point to a severe potential impact of global warming on the reproductive process of native S. maritima. Mitigation of global warming will be essential to maintain population persistence and support conservation and recovery of this halophyte that provides important ecosystem services in salt marshes.

Fusarium graminearum and Fusarium pseudograminearum caused the 2010 head blight epidemics in Australia

Wheat crops in southeast Queensland (Qld) and northern New South Wales (NSW) were infected with fusarium head blight (FHB)‐like symptoms during the 2010–11 wheat growing season. Wheat crops in this region were surveyed at soft dough or early maturity stage to determine the distribution, severity, aetiology and toxigenicity of FHB. FHB was widespread on bread wheat and durum, and Fusarium graminearum and/or F. pseudograminearum were diagnosed from 42 of the 44 sites using species‐specific PCR primers directly on spikelets or from monoconidial cultures obtained from spikelets. Stem base browning due to crown rot (CR) was also evident in some samples from both states. The overall FHB and CR severity was higher for NSW than Qld. Deoxynivalenol (DON) concentration of immature grains was more than 1 mg kg−1 in samples from 11 Qld and 14 NSW sites, but only 13 of 498 mature grain samples sourced from the affected areas had more than 1 mg kg−1 DON. DON concentration in straw also exceeded 1 mg kg−1 in eight Qld and all but one NSW sites but this was not linked to DON concentration of immature grains. The proportion of spikelets with positive diagnosis for F. graminearum and/or F. pseudograminearum and weather‐related factors influenced DON levels in immature grains. The average monthly rainfall for August–November during crop anthesis and maturation exceeded the long‐term monthly average by 10–150%. Weather played a critical role in FHB epidemics for Qld sites but this was not apparent for the NSW sites, as weather was generally favourable at all sites.

Physiological and proteomic approaches to address heat tolerance during anthesis in rice (Oryza sativa L.).

Episodes of high temperature at anthesis, which in rice is the most sensitive stage to temperature, are expected to occur more frequently in future climates. The morphology of the reproductive organs and pollen number, and changes in anther protein expression, were studied in response to high temperature at anthesis in three rice (Oryza sativa L.) genotypes. Plants were exposed to 6 h of high (38 °C) and control (29 °C) temperature at anthesis and spikelets collected for morphological and proteomic analysis. Moroberekan was the most heat-sensitive genotype (18% spikelet fertility at 38 °C), while IR64 (48%) and N22 (71%) were moderately and highly heat tolerant, respectively. There were significant differences among the genotypes in anther length and width, apical and basal pore lengths, apical pore area, and stigma and pistil length. Temperature also affected some of these traits, increasing anther pore size and reducing stigma length. Nonetheless, variation in the number of pollen on the stigma could not be related to measured morphological traits. Variation in spikelet fertility was highly correlated (r=0.97, n=6) with the proportion of spikelets with ≥20 germinated pollen grains on the stigma. A 2D-gel electrophoresis showed 46 protein spots changing in abundance, of which 13 differentially expressed protein spots were analysed by MS/MALDI-TOF. A cold and a heat shock protein were found significantly up-regulated in N22, and this may have contributed to the greater heat tolerance of N22. The role of differentially expressed proteins and morphology during anther dehiscence and pollination in shaping heat tolerance and susceptibility is discussed.

Maximizing seed and fodder production in Cenchrus species through foliar spray of growth promoters

An experiment was conducted during 2011 to 2013 at Western Regional Research Station (ICAR-Indian Grass- land and Fodder Research Institute), Avikanagar, Rajasthan, for evaluating the effect of foliar spray of different growth-promoters on seed yield and quality in Cenchrus species. The experiment was laid in randomized block design with 3 replications under rainfed condition. Foliar sprays of 3 growth-promoters, thiourea (0.25, 0.50 and 0.75%), GA (50, 100 and 150 ppm), KNO (2, 4 and 6%) were applied at panicle-initiation stage on IGFRI 3108 3 3 cv. of buffel grass (C. ciliaris L.) CAZRI 392 cv. of birdwood grass (C. setigerus Vahl). In C. ciliaris, foliar spray of 0.5% thiourea, 100 ppm GA and 4% KNO increased seed yield by 39, 31 and 50% respectively, over the control. 3 3 Similarly, in C. setigerus application of these growth-promoters at the same concentration showed increment in seed yield by 46, 39 and 60%, respectively, over the control. Proportion of spikelets with seed increased signifi- cantly by 0.25% thiourea, 50 ppm GA and 2% KNO by 12, 18 and 24%, respectively, in C. ciliaris, while in C. 3 3 setigerus 0.5% thiourea, 100 ppm GA and 4% KNO found optimum dose that increased proportion of filled seed 3 3 by 26, 20 and 31% respectively. The foliar application significantly increased germination and seedling length. Dry fodder yield increased by 0.50% thiourea, 100 ppm GA and 4% KNO with high magnitude, viz. 30, 49 and 41% 3 3 and 40, 47 and 47% in C. ciliaris and C. setigerus respectively.

Resource allocation patterns in Spinifex sericeus R.Br.: A dioecious perennial grass of coastal sand dunes

AbstractThe resource allocation patterns within populations of Spinifex sericeus R.Br, were studied on the mid north coast of NSW. Sand burial and nutrient availability were two major factors influencing the allocation of resources to roots, culms, tillers and inflorescences, resulting in different growth forms in different sections of the dune. The data suggest that pollen availability may affect allocation to seeds late in the flowering season.Spinifex sericeus was found to have a greater below‐ than above‐ground biomass, especially on the crest of the incipient foredune where sand accretion was high. The ability of culms of S. sericeus to grow upwards at a rate that generally prevents complete burial of the tillers is one mechanism which allows S. sericeus to vary resource allocation patterns in response to a varying environment.Differences in the inflorescence characteristics of males and females indicate their different functions. The much greater floret number of males indicated the importance of pollen dispersal. Female inflorescences consisted mainly of structures other than florets and suggested the importance of the female inflorescence in seed dispersal.Addition of nitrogen and phosphorus increased the number of spikelets and seeds but not the proportion of spikelets which produced seed.

Weight Compensation of Undamaged Kernels in Response to Damage by Sorghum Midge (Diptera: Cecidomyiidae)

The relationship between level of sorghum midge, Contarinia sorghicola (Coquillett), damage and weight of undamaged kernels, panicle sterility, and kernel weight was investigated in midge resistant and susceptible sorghum, Sorghum bicolor (L.) Moench, hybrid cultivars. A significant inverse relationship existed between the proportion of spikelets destroyed by midges and the weight of undamaged kernels in two of three susceptible hybrids as well as in three of seven case for two resistant hybrids. In only one trial involving a midge resistant hybrid was there a positive correlation between the two variables. However, these relationships were generally not significant at levels of damage below 40%. A significant positive relationship between the percentage of sterile panicle spikelets and of developed kernel weight occurred in half of the cases. Results of this study signify that for midge damage levels near economic threshold levels, the percentage of spikelets damaged by midges was approximately equal to percentage of yield loss—i.e., there was no compensation for midge damage. Partial sterility did not simulate midge damage.

A comparison of spring barley grown in England and in Scotland. 1. Shoot apex development

SummaryAn analysis of development of Golden Promise and Maris Mink spring barley grown in England and in Scotland was made in 1976 and 1977. In both seasons the differences between varieties at a site were small. Rates of leaf emergence and primordium production and the number of primordia formed and the number which died were almost the same at both sites in 1976. In 1977 both leaf emergence and ear initiation started later in Scotland and the rates of leaf emergence and spikelet initiation were slower. Fewer spikelet primordia were formed in Scotland than in England in 1977 but a higher proportion survived to produce potentially fertile florets. Tillers emerged at the same leaf stage of the main shoot and the frequency of tillering differed at some tiller positions between England and Scotland, but the number of tillers produced was similar at both sites.These results show that in Scotland the effect of longer photoperiod which enhances the rate of leaf emergence and primordium production compensates for the lower temperature which slows down these processes. The lower temperature in Scotland particularly in 1977 during the period of spikelet primordium death increased the proportion of spikelets that survived.