Department of Botany

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Now showing 1 - 20 of 103
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    Enhancing Germination of Seeds of a Multipurpose Tree Species Combretum molle
    (College of Natural and Applied Sciences, University of Dar es Salaam, 2022-12-21) Andrew, Samora Macrice
    Combretum molle R. Br. ex G. Don (Combretaceae) is a highly valued indigenous multipurpose tree species that has gained considerable attention in recent times due to its importance as a medicinal plant as well as an alternative species for wood and charcoal production. However, we lack adequate information on simple and appropriate methods that could be used to break its distinct seed dormancy to support domestication of wild populations apparently undergoing over exploitation and the negative impacts of deforestation. Eight pre-treatment methods involving complete removal of wing, complete removal of mesocarp, overnight soaking in cold water (24 °C) and partial removal of wing by scorching with fire, and their combinations were tested against the seed dormancy. Of all, the complete removal of mesocarp and overnight soaking in cold water followed with additional soaking in cold water for 24 h took the shortest imbibition (2 days) and germination (7 days) periods, highest germination value (76) and germination energy (80%). Similarly, the same treatment scored significantly (P < 0.05) higher cumulative germination of 72%. To obtain best germination traits, C. molle seeds should be pre-treated by removing the mesocarp and overnight soaking in cold water followed with additional soaking in cold water for 24 h, before sowing. These results have wide implications including supporting domestication and forest landscapes restoration in Tanzania.
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    Understanding responses to climate-related water scarcity in Africa
    (Elsevier, 2022) Filho WL, Totin E., Franke JA., Andrew S.M., Abubakar IR., Azadi H., Nunn PD., Ouweneel B., Williams PA. and Simpson NP
    Water scarcity is a global challenge, yet existing responses are failing to cope with current shocks and stressors, including those attributable to climate change. In sub-Saharan Africa, the impacts of water scarcity threaten livelihoods and wellbeing across the continent and are driving a broad range of adaptive responses. This paper describes trends of water scarcity for Africa and outlines climate impacts on key water-related sectors on food systems, cities, livelihoods and wellbeing, conflict and security, economies, and ecosystems. It then uses systematic review methods, including the Global Adaptation Mapping Initiative, to analyse 240 articles and identify adaptation characteristics of planned and autonomous responses to water scarcity across Africa. The most common impact drivers responded to are drought and participation variability. The most frequently identified actors responding to water scarcity include individuals or households (32%), local government (15%) and national government (15%), while the most common types of response are behavioural and cultural (30%), technological and infrastructural (27%), ecosystem-based (25%) and institutional (18%). Most planned responses target low-income communities (31%), women (20%), and indigenous communities (13%), but very few studies target migrants, ethnic minorities or those living with disabilities. There is a lack of coordination of planned adaptation at scale across all relevant sectors and regions, and lack of legal and institutional frameworks for their operation. Most responses to water scarcity are coping and autonomous responses that showed only minor adjustments to business-as-usual water practices, suggesting limited adaptation depth. Maladaptation is associated with one or more dimension of responses in almost 20% of articles. Coordinating institutional responses, carefully planned technologies, planning for projected climate risks including extension of climate services and increased climate change literacy, and integrating indigenous knowledgewill help to address identified challenges of water scarcity towards more adaptive responses across Africa.
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    Drivers, trends and management of forest plantation fires in Tanzania
    (Elsevier, 2022) Andrew, Samora Macrice
    During the last two decades there has been an increase in investments in exotic woodlots and commercial forest plantations in Tanzania. However, fire has repeatedly been singled out as number one risk to forestry plantations investments and improved management is urgently needed to reverse the trend and ensure sustainable supply of forest products. Unfortunately, little has been documented on major drivers, trends and management of exotic woodlots and forest plantation fires in Tanzania. Lack of such information has slowed down and diminished efforts to reduce the negative impacts of these fires and upscaling of commercial forestry. This paper analyses few available published information and gray literature as well as satellite imagery for 2016–2020 to put together drivers, trends and management of forest plantation fires. To effectively control fires, it is important that forest policy is enforced, education and awareness on fires is enhanced, local communities support is promoted and fire prevention and suppression is strengthened in Tanzania.
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    Production and nutritional value of Pleurotus floridanus grown on rice straw supplemented with Leucaena leucocephala foliage
    (Elsevier, 2023) Andrew, Samora Macrice
    Edible mushrooms are increasingly recognized to offer health, environmental and socio-economical benefits across the globe. However, long cultivation time and low nutritional value of harvested mushrooms have remained the limiting factors for taping the benefits and sustainable production in developing counties. There is therefore a need to seek for alternative substrate formulations that would shorten cultivation time, increase the nutritional value of mushrooms as well as ensure environmental sustainability. This study examined the potential of using nutrient and biomass rich Leucaena leucocephala (Lam.) de Wit foliage in combination with the rice straw (traditional substrate) to bolster production and nutritional value of Pleurotus floridanus mushroom in Morogoro, Tanzania. Mushrooms were grown in 30 × 40 cm 1.6 kg dry weight polythene bags in a randomized complete block design experiment with five treatments. The shortest cultivation period (average of 21 days) which stemmed largely from spawning to full mycelia colonization was attained when 5% Leucaena foliage was mixed with the rice straw. There was a significant (p < 0.05) increase in protein content from 23.3 to a maximum of 29.8%, when rice straw was supplemented with the 5% Leucaena, while further increase in Leucaena supplementation caused a lowering of crude protein content. There were significant increases (P < 0.05) in the contents of copper and calcium minerals when 5% of Leucaena foliage was incorporated into the growing substrate. Thus, to increase production cycle and contents of protein and essential minerals, addition of 5% of L. leucocephala foliage is recommended during production of P. floridanus using rice straw, for sustainability.
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    Land cover change and utilization of village land forest reserves in Ludewa, Tanzania
    (Elsevier, 2023) Andrew S.M.., Nyanghura Q.M., Mombo F.M.
    Knowledge of land cover change and associated driving factors is important for developing improved management strategies and future monitoring of tropical forests. We present here for the first time the case of two forest reserves (Litwang’ata and Intake) in Ludewa district, Southern Highlands Tanzania. These reserves were recently (2019) declared Village Land Forest Reserves (VLFRs), with their management and ownership devolved to their communities. We used remote sensing and GIS methods to assess spatial-temporal land cover change of the two VLFRs for the period 1996–2016. We also used household interviews (HHIs), focus group discussions (FGDs) and key informants’ interviews (KIIs) to examine the perceived socio-economic drivers of land cover change and the household forest-based incomes derived from the VLFRs. Our findings overall showed that closed woodland decreased by 780.3 ha whereas open woodland, grass/shrub land and agricultural land increased by 700.9 ha, 71.7 ha and 50.9 ha, respectively. Wildfires are perceived as the major drivers of land cover change. To a large extent, local communities utilize VLFRs for their livelihoods, with major resources extracted being firewood, construction poles, fresh water and thatch grass. Of the total forest-based income, logging for timber accounted for about 33% for Intake VLFR users and 36% for villagers who utilize resources from Litwang’ata VLFR. Future monitoring of land cover and livelihood changes is recommended for sustainable forest management.
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    Growth and Yield Performance of Selected Upland and Lowland Rainfed Rice Grown in Farmers and Researchers Managed Fields at Ifakara, Tanzania.
    (Academic journal, 2019-01-24) Kitilu, M. J. F.; Nyomora, Agnes M. S.; Charles, J.
    Bridging the yield gaps is of major concern to rice breeders and agronomists under rainfed rice cultivation. The yield performance of lowland and upland rainfed rice varieties was investigated in farmers’ and researchers’ field conditions at four locations in Ifakara. Selected agronomic practices namely; recommended fertilizer (80 kgN/ha), spacing of 20 cm × 20 cm, weed free fields and high yielding varieties of TXD306, Komboka and Tai for lowland rainfed, and NERICA1, NERICA2 and NERICA4 for upland rainfed rice. Moreover, farmer selected varieties Supa India and WahiPesa were used as the local control in this research. The study revealed that yield performance of lowland rainfed rice varieties and in farmers’ fields ranged between 2.9 and 6.9 t ha-1, while in the upland rainfed rice the yield ranged between 2.5 and 5.4 t ha-1. This was similar to yield that was obtained from the researchers’ fields which ranged between 2.4 and 8.5 t ha-1 in lowland and between 1.8 and 4.8 t ha-1 in upland fields. The yield gap analysis revealed that the gap of between 35 and 60% previously reported in lowland rice was narrowed to 0 to 12.1%, while in the upland rice from 24.5 to 28.6% previously reported to 0% and excess yield over the potential yields and yields previously reported by farmers. The performance of all improved rice varieties at farmers and researchers’ field were significantly higher compared to the local check varieties Supa India and WahiPesa. It was concluded that, providing farmers with selected good agronomic practices and supervision of farmers in field management activities enhanced rice productivity under farmers’ conditions and narrowed or bridged the yield gaps that existed.
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    Food security: The role of urban and peri-urban agriculture. A case of Dar es Salaam City, Tanzania
    (INNSPUB, 2018-08-04) Malekela, Asnath. A; Nyomora, Agnes M.S.
    This study examined the contribution of urban and peri-urban agriculture (UPA) on food security in Dar es Salaam city. With the massive population increase in most cities in the world, food insecurity has become a challenge. One of the responses to this is promotion of urban and peri-urban agriculture (UPA). Primary and secondary data were collected using structured questionnaires, in-depth interviews, direct observations, focus group discussions and literature survey. About 201 respondents engaging in urban and peri-urban agriculture were interviewed. Also, 100 local market traders from 10 local markets, and 7 supermarket managers from 7 representatives supermarkets in Dar es Salaam city were interviewed. The Statistical Package for Social Sciences (SPSS) version 20 was used to analyze the data. The findings revealed that UPA had a positive contribution to food security as it was observed that the main aim of 84% of the farmers who engaged in crop production was to get food and income. In the surveyed local markets about 47% of food products were sourced from UPA, also, 6080% of vegetables and 57.1% of the eggs sold in the surveyed supermarkets were sourced from UPA. The study recommends adoption of modern technology for better output with use of limited land and water resources. Also available policies supporting UPA should be reviewed for its sustainable development.
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    Optimal Weeding Period for Groundnuts (Arachis Hypogea L.)
    (1988) Rulangaranga, Z. K.; Banyikwa, Feetham F.
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    Determinants of Woody Cover in African Savannas
    (2005) Sankaran, Mahesh; Hanan, Niall P.; Scholes, Robert J.; Ratnam, Jayashree; Augustine, David J.; Cade, Brian S.; Gignoux, Jacques; Higgins, Steven I.; Le Roux, Xavier; Ludwig, Fulco; Ardo, Jonas; Banyikwa, Feetham F.; Bronn, Andries; Bucini, Gabriela; Caylor, Kelly K.; Coughenour, Michael B.; Diouf, Alioune; Ekaya, Wellington; Feral, Christie J.; February, Edmund C.; Frost, Peter G. H.; Hiernaux, Pierre; Hrabar, Halszka; Metzger, Kristine L.; Prins, Herbert H. T.; Ringrose, Susan; Sea, William; Tews, Jörg; Worden, Jeff; Zambatis, Nick
    Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties1, 2, 3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1, 2, 4, 5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ~650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered ‘stable’ systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ~650 mm, savannas are ‘unstable’ systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation6 may considerably affect their distribution and dynamics.
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    Semi-viviparous Embryo Development and Dehydrin Expression in the Mangrove Rhizophora Mucronata Lam.
    (2010) Tibazarwa, Flora I.; Nitsch, L. M. C.; Wolters-Arts, M. M. C.; Mariani, Celestina; Derksen, J. W. M.
    Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55–65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6–8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression.
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    Shades of Green: Conservation in the Developing Environment of Tanzania
    (2013) Tibazarwa, Flora I.; Gereau, Roy E.; Raven, Peter H.; Sodhi, Navjot S.; Gibson, Luke
    In this chapter, two conservation areas, Lake Natron and Kitulo Plateau, are used to exemplify the challenges and delineate best practices, with Kitulo presenting a notable example of conservation to be emulated. The chapter demonstrates the challenges to and opportunities for achieving sustainable development in Tanzania, based on two development projects. One is a soda ash extraction project and the other a dairy farm converted to a national park. In particular, the chapter focuses on the gray areas where benefits are considered losses and vice versa and the realities of striving towards a balance between development and conservation. Lake Natron and Kitulo National Park are protected for their biodiversity and conservation value under Tanzanian policies and legislation for natural resource management.
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    Cross Compatibility of Cultivars of Gossypium Hirsutum L. and Feral Gossypium Barbadense L. in the Southern Highlands of Tanzania
    (2012-12) Shilla, O.; Hauser, T. P.; Tibazarwa, Flora I.
    Cotton is the second most important cash crop contributing about 15% to the annual foreign earning in Tanzania and is purely from Gossypium hirsutum L. cultivars. Gossypium barbadense L., a textile source in other parts of the world occurs as a feral perennial of ornamental and medicinal value in home gardens. G. barbadense L. is a natural host of the red bollworm, a destructive pest to cotton. The Southern Highlands (SH) of Tanzania have been quarantined from cotton production to control spread of the red bollworm to other growing areas. Transgenic cotton expressing the delta-endotoxin genes from Bacillus thuringiensis (Bt) offers an alternative control to the pest and reduced dependence on insecticide. Gene flow between wild or valued feral relatives and transgenic crops is a biosafety concern should transgene escape result in resistance development and contamination of germplasm. Potential gene flow between feral G. barbadense (including accessions Gb1 and Gb2) from the SH and G. hirsutum cultivars was assessed using controlled hybridization. The crosses produced fertile F1 but intraspecific seeds from G. barbadense did not germinate. G. barbadense is more likely to receive than donate genes implying development of pest resistance if introgressed filial generations express the Bt product.
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    The Growth Response of Two East African Perennial Grasses to Defoliation, Nitrogen Fertilizer and Competition
    (1988) Banyikwa, Feetham F.
    Two East African perennial grasses, Digitaria macroblephara (Hack) Stapf. and Sporobolus ioclados (Trin.) Nees, were grown in pure and mixed culture in a factorial treatment design of defoliation, nitrogen fertilizer and plant density for a period of 90 d. With regard to controls, defoliation reduced total yield of both species per plant by 81%; higher density decreased total yield per plant by 56%; and intraspecific competition decreased total yield per plant 24% more than interspecific competition. High nitrogen promoted total yield per plant by 168%. Total yield per plant of D. macroblephara was 3.2 times greater than that of S. ioclados. With defoliation, density dependent competition decreased total yield per plant by 42% while, without defoliation, density dependent competition decreased total yield per plant by 601%. With defoliation, high nitrogen increased yield per plant by 9% while without defoliation high nitrogen increased yield per plant by 315%. The results suggest that the magnitude of the negative aspects of density dependent competition may be lessened by defoliation and growing plants in mixed culture. It is concluded that in grazing ecosystems it may be advantageous to grow plants in mixed culture since the negative effects of interspecific competition are less than those arising from intraspecific competition.
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    The Physical and Chemical Characteristics of a Phycocolloid from the Red Alga Sarcodia Montagneana j. Agardh of Tanzania
    (1987) Semesi, A. K.; Banyikwa, Feetham F.
    A phycocolloid from Sarcodia montagneana has been evaluated by chemical and physical analyses. The study has revealed that the phycocolloid has a yield of 39.6 per cent (percentage dry weight of alga), an IR spectrum similar to that reported for .lambda.-type carrageenan, an SO4-2 content of 22.5 per cent, a 3, 6-anhydrogalactose content of 5.1 per cent, a galactose content of 51.5 per cent (percentage dry weight of phycocolloid) and a negative optical rotation. The polysaccharide does not form a gel and cannot be modified by alkaline borohydride. It may be used in the food industry as an emulsifying agent.
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    Species-Habitat Relationships in The Serengeti Short Grasslands, Tanzania
    (1989) Banyikwa, Feetham F.
    An improved principal components analysis ordination is used to study grass-habitat relationships in the Serengeti short grasslands. Species distribution is found to be influenced by soil factors along a topographic gradient.
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    Temporally Variable Rainfall Does not Limit Yields of Serengeti Grasses
    (1998) Williams, Kevin J.; Wilsey, Brian J.; McNaughton, Samuel J.; Banyikwa, Feetham F.
    Temporally variable rainfall, on scales ranging from intraseasonal to decadal, is characteristic of the climate of dry grassland ecosystems. A growth chamber experiment indicated that the Serengeti ecosystem's most abundant and widespread grass, red oat grass (Themeda triandra), collected at locations with different rainfalls, growing seasons, and grazing intensities, is insensitive to an ecologically realistic range of rainfall events if the total amount of rain is constant. The result was confirmed under field conditions since plots did not respond to different temporal variances in water supply, although they did respond to levels of water supply. The results suggest that these grasses are water "spenders", using it as fast as they can when it is abundant, and then being semi-dormant in intervals between downpours. This characteristic could provide a competitive advantage in environments characterized by infrequent thundershowers. The ability to tolerate intervals between showers without losing living tissues, or dying, can contribute to the success of grasses in highly variable climates, and will tend to quench potentially drastic fluctuations of energy flow through the food web.
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    Promotion of the Cycling of Diet-Enhancing Nutrients by African Grazers
    (1997) McNaughton, S. J.; Banyikwa, Feetham F.; McNaughton, M. M.
    Experiments in Serengeti National Park, Tanzania, provide direct evidence that large, free-ranging mammalian grazers accelerate nutrient cycling in a natural ecosystem in a way that enhances their own carrying capacity. Both nitrogen and sodium were at considerably higher plant-available levels in soils of highly grazed sites than in soils of nearby areas where animal density is sparse. Fencing that uncoupled grazers and soils indicated that the animals promote nitrogen availability on soils of inherently similar fertility and select sites of higher sodium availability as well as enhancing that availability.
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    Levels of ABA, its Precursors and Dehydrin-like Proteins During Mangrove Leaf Development and Senescence
    (2009) Tibazarwa, Flora I.; Masoud, M; Derksen, J. W. M.; Mariani, C.
    Abstract—Abscisic acid (ABA) and dehydrin proteins are thought to confer tolerance to plant tissue under physiological stress and drought. Rhizophora mucronata, a true mangrove species, is subjected to physiological drought from fluctuating high saline conditions where leaf loss or senescence is considered a possible regulation mechanism to combat stress. Levels of ABA and proteins that cross reacted with an anti – dehydrin antibody were assessed through development with the aim of correlating these factors to physiological water stress or salinity stress in R. mucronata leaves. Younger leaves showed lower levels of ABA than mature and senescing leaves. In situ production and translocation from mature to younger leaves may contribute to these observations. The presence of ABA in senescing leaves is thought to be due to the presence of low levels of physiological activity. Proteins detected by anti–dehydrin antibody require cDNA confirmation, but the visibly increasing intensity of a band at ~64kDa through development suggests potential correlation to drought or salinity stress which is expected to be maximal in maturing leaves. The absence of the dehydrin–like proteins in senescing leaves is postulated to be due to the lack of energy investment to synthesise these proteins in dying leaves.