Different Stages Of Flowering Research Articles

Change in Panicle Susceptibility Associated with Flowering Rate of Spikelets in Bacterial Grain Rot of Rice Caused by Pseudomonas glumae.

Change in susceptibility of rice spikelets (cvs. Koshihikari, Koganebare and Asominori) to bacterial grain rot, caused by Pseudomonas glumae, with time was examined by spraying bacterial suspension to panicles at different stages of flowering. Percentage of diseased spikelets of these varieties was highest when they were inoculated on flowering day and remained high when they were inoculated within 3 days after flowering. The disease was very low when spikelets were inoculated 2 days before or 4 days after flowering, even though spikelets were incubated under high humidity (RH<95%) condition for 24hr after inoculation. These results indicate that susceptibility of rice spikelets changes with time during a short, critical period before and after flowering and that high humidity at this stage is crucial to the infection of spikelets. Analysis on the relationship between susceptibility of a whole panicle and the flowering rate of spikelets within a panicle showed that panicle susceptibility depends on the rate of flowering per day after heading. This correlation indicates that susceptibility of rice plants to the disease in the field may be estimated from the heading rate of panicle in the field and from the extent of susceptibility of each panicle per day. The relative value for cumulative susceptibility of rice plants (Tt) in the field on the day t after first heading was represented by the value for total susceptibility of all panicles on the day t which was calculated by daily heading rate of panicles on days 0 to t after first heading in the field and by the panicle susceptibility on each day after heading. The Tt value of rice plants increased similarly from heading time, which is defined as the day when more than 40% of panicles have headed, and then decreased 5 to 6 days after heading time. Tt was very low about 12 days after heading time, suggesting that rice plants in the field are susceptible to the disease during a short length of time, i.e., from the heading time to about 11 days after that.

Influence of Harvest Time on Yield and Composition ofArtemisia annuaOil Produced in France

ABSTRACT The essential oils of Artemisia annua were isolated and analyzed at different stages of flowering using a combination of GC and GC/MS. At the peak of flowering, the proportion of artemisia ketone (the most abundant component) exceeded 50% and the oil yield was 0.4–0.5%.

Pollination Effects on Pearl Millet Ergot

Pollination of inflorescences of 3 male-sterile lines of Pennisetum americanum before, or at the same time as, inoculation with Claviceps fusiformis conidia reduced ergot to <3% of infected florets. Pollination 16 h after inoculation reduced ergot to 7-21% compared with 60-86% for inoculated, nonpollinated checks. Pollen germinated in 1 h when incubated in a 10% sucrose sol. whereas conidia did not germinate in <16 h of incubation. Results from inoculation of inflorescences of male-sterile lines at different stages of flowering in the absence of pollen, and observations on the effects of pollination on stigma morphology and longevity, lead to the conclusion that infection occurs mainly through the stigmas. Pollination protects against infection probably because it induces rapid withering of stigmas. The results help explain the increased ergot susceptibility of pearl millet F1 hybrids compared with traditional cvs., and have important implications for resistance screening and for the development of cultural control measures.ADDITIONAL ABSTRACT:Pollination of three male-sterile lines of Pennisetum americanum before or at the same time as inoculation with Claviceps fusiformis greatly reduced ergot infection and pollination 16 h after inoculation also reduced infection. Heaviest infection followed the inoculation of unpollinated inflorescences at the stage when most stigmas were receptive. It is suggested that pollination protects against infection by inducing rapid withering of the stigmas, and that the observed susceptibility of F1 hybrids, compared with traditional varieties, is caused by delayed pollination. It is emphasized that plants being screened for ergot resistance should not become pollinated before inoculation and it is suggested that ergot control in F1 hybrids may be improved by selecting for reduced protogyny or by growing an early-flowering variety with hybrid crops