Browsing by Author "Nyomora, Agnes"

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    Assessment of African Blackwood (Dalbergia melanoxylon) Population Structure in Kilwa District, Tanzania
    (Tanzania Journal of Science, 2021-10-30) Washa B., Washa; Nyomora, Agnes; Nnungu, Stephen I
    Overharvesting and limited conservation efforts have posed a serious threat to future availability of Dalbergia melanoxylon in Tanzania in recent years. The study was conducted between 2018 and 2020 covering Mitarure Forest Reserve (MFR) and 2 surrounding community forests of Ngea and Nambawala in Kilwa District. The purpose of the study was to assess the existing population status of the species in Tanzania. A total of 36 circular plots in Mitarure and 15 plots in each community forest were laid down. Data were recorded for the number of stems per plot, and then converted on per hectare basis where the basal area and densities per hectare were calculated. Data was disaggregated into 5 Diameter at Breast Height (DBH) generated distribution classes ranging from DBH 0 to more than 45 cm. The results revealed that, there was a contrast between the Mitarure Forest Reserve and community forests in terms of individual number of trees per unit area, basal area and densities. The numbers of stems per hectare for the species were found to be 16, 10 and 8 stems/ha in Mitarure, Ngea and Nambawala forest, respectively. Dalbergia melanoxylon in Mitarure forest was normally distributed. The respective basal area was over 80 m2 per ha in Nambawala against over 60 in MFR and Ngea. The results suggest success of the communities in conserving the species after previous overharvest. Authorities should frequently visit forests to increase the population of the species and reduce unauthorised harvesting.
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    Expression of Genes for The Biosynthesis of Compatible Solutes During Pollen Development Under Heat Stress in Tomato (Solanum Lycopersicum)
    (Elsevier, 2015-02) Sangu, Emmanuel; Tibazarwa, Flora I.; Nyomora, Agnes; Symonds, Rachael
    Accumulation of compatible solutes is considered a key adaptation mechanism in many plants in response to abiotic stress. The expression of four genes, involved in sucrose metabolism (SPS and SuSy), biosynthesis of galactinol (GoLS1) and proline accumulation (P5CS) was compared: at meiosis (MM), vacuolated and mature stages of pollen development in heat tolerant and heat sensitive tomato genotypes. The results showed differences in gene expression across tomato genotypes and stages of pollen development. Three genes (P5CS, SPS and SuSy) were up regulated in heat tolerant genotype CLN1621L at the mature stage and one gene (P5CS) in genotype CLN5915-93D at the MM stage. Two genes (SPS and GoLS1) were down regulated in heat sensitive genotype CA4 and one gene (GoLS1) in genotype CLN2498E at the MM stage. Additionally, the continuous exposure of tomato genotypes to temperatures of 35°C/28°C day/night completely impaired flower development in genotypes CA4 and CLN2498E but not in genotypes CLN1621L and CLN5915-93D. Tomato genotypes CLN1621L and CLN5915-93D produced fully developed flowers containing mixture of non viable pollens and very few viable pollens grains. Membrane permeability was affected at all stages of development under heat stress with heat tolerant genotypes CL5915-93D4, CLN2498E and CLN1621L showing varying degrees of heat acclimation. Significant increases in total chlorophyll were seen in all genotypes in response to heat stress. The expression of compatible solute genes at MM is more critical than at mature stage for the development of viable pollen grain. Copyright © 2015 Elsevier GmbH. All rights reserved.