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No description available.

No description available.

No description available.

In this investigation aimed to identify and understand the fungus responsible for the production ofHT-2 and T-2 mycotoxins in UK oats, Fusarium langsethiae was found to be the causal species. A quantitative competitive PCR (QC-PCR) and a real-time PCR assay for quantifying F langsethiae biomass in plant material were successfully developed. Real-time PCR was found to have a wider range of quantification than QC-PCR. In glasshouse experiments, point inoculation technique and high spore load (106 spores mr)) were found to significantly increase (P = 0.036 and 0.016 respectively) the level of F langsethiae infection in oat panicles. HT-2 and T-2 appeared to increase in line with the level of infection. For both glasshouse and field experiments, all inoculatiQn methods failed to achieve high levels of infection and high levels of HT-2 and T-2 observed in some commercial fields. Detached leaf assays showed some host preference of F langsethiae towards oats than wheat. Lesion lengths were longest on leaves of an oat cultivar (Gerald) that has been reported to accumulate highest HT-2 and T-2 and shortest on leaves of the cultivar (Millennium) reported to accumulate the lowest levels of these mycotoxins. Fusarium langsethiae was not found to be a seedling blight pathogen of oats and wheat in a controlled environment study comparing its pathogenicity with those of known Fusariu11l and Microdochiu11l species. Fusariu11l langsethiae is therefore unlikely to reduce crop stand and yield where infected seeds are sown. Fusariu11l langsethiae failed to produce visual symptoms in infected oat panicles or wheat ears in all experiments and in commercial oat fields surveyed. However, all evidence indicates that it is responsible for high concentrations of HT-2 and T-2 in oats, consequently the presence of this fungus in oats is important in human and animal health.

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No description available.

No description available.

The arrangement of outer three layers (i.e. dermatogen, hypodermis, and subhypodermis) in the spikelet apex and floret primordium is similar to that of the vegetative apex. In their origins the lemma, palea, lodicules, carpel and integuments are leaf-like, whereas the floret and stamen primordia are similar to axillary buds. The integuments arise almost entirely from the repeated divisions of dermatogen cells, Each stigmatic hair develops by the elongation and characteristic division of a single epidermal cell of the stigma. A main vascular strand enters the base of each lodioule and by repeated divisions forms a ramification throughout the lodicule. The procambium appears as an isolated patch of tissue in the position of the future median and lateral strands of the carpel and of the single strand of the stamen. The first appearance of the procambium is restricted to the middle region of the future longitudinal course of the strand. From this point of origin each procambial strand continues its initiation both acropetally and basipetally. A similar pattern of origin and differentiation has been observed for the initiation and propagation of the first protophloem element. It holds also for the first element of protoxylemin the stamen. In the funicular strand the differentiation of the pro-cambium and the vascular elements is acropetal. Comparable stages in the initiation of the carpel and the differentiation of the procambium have also been observed in Avena, Oryza and Secale. The significance of the above observations is discussed. Some observations are also made on the ultra structure of differentiating protophloem elements of the stamen.

The role of the root cap in graviperception was studied in root tips of Maize seedlings. It was shown that destarching and removal of the root cap causes the lose of geotropic reaction in the roots. The normal growth of the roots is not affected by this decapping and the roots regenerate their root caps during 36 hours. Geotropic reactivity reappears before the completion of regeneration and a study of recovery time was made. A relationship between the length of the roots at decapping time and the length of recovery period was found. Presentation time studies of normal roots and roots which were decapped after stimulation indicate that the root cap can be removed after stimulation without influencing the subsequent response. It was also shown that the stimulus must be transmitted within the presentation time and that the plasmatic connections between the cap and the root are necessary for this transmission. The structural state of the root cap at recovery time was investigated with the Electron Microscope and the presence of starch grains shown. The results of this work are discussed in the light of the current theories on graviperception.