A field experiment was conducted in Tanzania for two seasons to assess the genetic diversity of bambara groundnut landraces based on morphological characters. One hundred accessions collected from a wide range of agricultural zones in the country were evaluated in a 10 · 10 triple lattice block design at Maruku station in Bukoba, Tanzania. For the qualitative characters evaluated, considerable morphological variations were observed for growth habit, pod shape and pod colour. Quantitative morphological characters such as peduncle length, number of leaves per plant, terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant length, pod width, seed length, seed width, number of pods per plant, shelling percentage and days to 50% flowering showed significant variation among accessions for the two test seasons. Multivariate analysis for 15 quantitative morphological traits that showed significant variation indicated that the first four PCs with eigenvalues ‡1 accounted for 63.0 and 65.0% of the total variance among the accessions during the two test seasons, respectively. The most important loadings for PC1 and PC2 for the two seasons were terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant height and pod length, pod width, seed length, seed width, numbers of pods per plant. Cluster analysis grouped bambara groundnut accessions into three major groups with respect to their geographic origins. Based on this present study, bambara groundnut landraces from Tanzania displayed a considerable diversity for morphological and agronomic traits useful for germplasm management and utilization into crop improvement.

seed production and, hence, the seed pool and future weed population, suggesting that fertilize r usage can be exploited in an integrated programme of ciopiwecd management. A trend towards lower N fertilizer application owing lo concerns about the environment willlavour most of the weed spedes investigated in these experiments and change the composition of weed populations.The effects of nitrogen fertilizer on the growth and density of natural weed populations io spring barley (Hordeum vuigare L.) and winter wheat (Trlticum aestivum L.) were investigated in the absence of herbicide. An increased level of applied nitrogen did not enhance: weed germination, tended to decrease the total weed biomass and had a differential effect upon the biomass of individual weed spedes ia both wheat and barky. In competition with barley, Chenopodium album L. and Lamlum spp. had lower nitrogen optima ihan the crop, while Urtica wens L. had a higher nitrogen optimum. In competition with wheat, Stellaria media (L.) Vill., Lamium spp. and Veronica spp. had lower nitrogen optima than the crop. The systematic changes in nitrogen effect with time were analysed by fitting orthogonal polynomials to the growth and density curves. The methodology could be recommended for other studies in which time or other systematic factors are included, as it supplies information which a traditional analysis of variance cannot provide. Since seed production is positively correlated with biomass, so nitrogen level affects

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Cells in mitosis can be flow cytometrically discriminated from GI, S, and GZ cells by analysis of a nuclear suspension prepared with nonionic detergent, fixed with formaldehyde, and stained with mithramycin, propidium iodide, or ethidium bromide. With these DNA-fluorochromes, the fluorescence is quenched by formaldehyde less in mitotic nuclei than in interphase nuclei. Mitotic nuclei have a 20-4095 increased mithramycin fluorescence and 3040% decreased light scatter in comparison to those of Gz nuclei. There is a high correlation (r = 0.95; P < 0,001) between microscope counts of mitotic figures in smear preparations of the initial cell suspension and the flow cytometrically estimated fraction of nuclei with increased mithramycin fluorescence. Flow sorting (FACS) demonstrates that the mitotic nuclei are confined to the peak of increased mithramycin fluorescence and decreased light scatter. The method has been applied to cultures of Yoshida ascites tumor cells, JR-1 reticulosarcoma cells, and PHA-stimulated human lymphocytes, incubated in the presence or absence of vinblastine for mitotic arrest. In a heteroploid mixture of fixed Yoshida (near-diploid) and JB-1 (hypotetraploid) nuclei, the mitotic fractions of the two cell lines could be estimated separately when analyzed with mithramycin fluorescence versus light scatter or with mithram ycin fluorescence versus propidium iodide fluorescence.Key terms: Mitosis, flow cytometry, mithramycin, propidium iodide, ethidium bromide, cell cycle analysis, cell sorting, aneuploidyThe fraction of mitotic cells is an important parameter in cell population kinetic analysis, especially for the estimation of a cell population's birth rate by experimental arrest of cells in the mitotic metaphase with colcemid or vinblastine (1). With quantitative DNA analysis by flow cytometry, the mitotic fraction is not measured specifically but accumulated in the same histogram peak as G2 cells. However, useful methods for specific estimation of the mitotic fraction by flow cytometry have been developed based on differential denaturation of chromatin with acid or heat to change the redgreen fluorescence ratio of the metachromatic dye acridine orange (4-7), or based on differential staining of nuclear protein with fluorescein isothiocyanate in preparations counterstained with propidium iodide (10).It has been shown with acridine orange that formaldehyde alters the resistance of chromatin to heat denaturation differently in interphase and metaphase cells (5). It has also been reported that the GZ+M peak in DNA profiles of formalin-fixed and mithramycin-stained cells is extremely broad and not suited for cell cycle analysis (3). Recently, it has been demonstrated by flow sorting of rabbit ovary cell suspensions fixed in ethanol and formaldehyde/glutaraldehyde and stained with mithramycin that meiotic prophase cells and mitotic cells are more fluoi-escent than GZ cells and GI doublets (8).In this paper, we demonstrate that formaldehyde fixation at room temperature and at neutral pH alters the

Drought adaptation strategies of two bambara groundnut landraces, Uniswa Red and S19‐3, collected from contrasting environments in Africa, were compared. Our objectives were to investigate the relative significance of effective stomatal control induced by the abscisic acid (ABA) signalling and osmotic adjustment in regulating plant water relations in general for this legume species. The ABA concentration [ABA] in the leaf increased linearly with declining relative leaf water content, and there were significantly higher [ABA] in Uniswa Red compared with S19‐3 at the final harvest in the drought‐stressed plants. Estimated by a linear‐plateau model, S19‐3 initiated the reduction in transpiration at a significantly lower soil water threshold (FTSW = 0.50 ± 0.024) than Uniswa Red (FTSW = 0.69 ± 0.023) indicating that the latter was more sensitive in reducing plant water use in response to soil drying. A similar trend was found for stomatal closure during soil drying, although the soil water thresholds at which relative stomatal conductance (gs) started to decline were not significantly different between the two landraces. By an early closure of stomata and hence an early reduction in transpiration rate during soil drying, Uniswa Red could be defined as a ‘water‐saver’ such that it maintains leaf water status to a great extent of soil water deficit. This strategy is important for survival during intermittent drought. While S19‐3 could be defined as a ‘water‐spender’ with a late closure of stomata, hence a late declining of transpiration rate during soil drying allowed the landrace to maximize its water use despite giving up its leaf water relations. Such drought response together with a fast phenological development of S19‐3 indicates that the landrace is capable of escaping from terminal drought while maximizing its water use and productivity when soil water is available.

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