Plant growth, water relations and transpiration of two species ofAfrican nightshade (Solanum villosum Mill. ssp. miniatum(Bernh. ex Willd.) Edmonds and S. sarrachoides Sendtn.)under water-limited conditions

Department of Horticulture, Jomo Kenyatta University of Agriculture and Technology, Nairoba, Nairobi Area, Kenya
Scientia Horticulturae (Impact Factor: 1.5). 09/2006; 110(1). DOI: 10.1016/j.scienta.2006.06.003

ABSTRACT The adaptation to drought stress of two African nightshade species, Solanum villosum and S. sarrachoides was investigated in pot and field experiments between 2000 and 2002. Two genotypes of S. villosum (landrace and commercial) and one accession of S. sarrachoides were grown under droughted, moderate stress and well-watered conditions. Leaf expansion, stem elongation and transpiration began to decline early in the drying cycle with fraction of transpirable soil water (FTSW) thresholds of 0.46–0.64. Osmotic adjustment (OA) of both species was in the range of 0.16–0.19 MPa and could not maintain positive turgor below water potentials of À1.80 to À2.04 MPa. The responses evaluated were similar in the three genotypes suggesting similar strategies of adaptation to drought stress. Under field conditions, the S. sarrachoides accession showed a higher leaf area than the S. villosum commercial genotype. It is concluded that the three African nightshade genotypes have limited OA capacity and adapt to drought mainly by regulating transpiration. This was achieved by reduction of leaf area. In general, it is necessary to maintain FTSW above 0.5– 0.6 to prevent decline in leaf expansion, stem elongation, and transpiration.

1 Bookmark
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Soil texture and evaporative demand have been reported to be the main factors which influence the transpirational response to soil water deficits. However, experimental evidences are not enough. The objective of this study was to investigate the transpirational response to soil water availability in soils of different textures under different evaporative demand levels. The three main soils of the Loess Plateau of China (loamy clay, clay loam and sandy loam) were selected and six constant soil water treatments were applied for winter wheat (Triticum aestivum L.) grown in pots. In order to reduce the influence of environmental conditions and plant factors, a normalized daily transpiration rate was used to develop the relationships with volumetric soil water content and soil water suction. Results showed that, under various levels of evaporative demand, a linear-plateau function with a critical value could be used to describe the dynamic change of the normalized transpiration rate with soil drying. Soil texture significantly influenced both the critical and the slope values of the linear-plateau equations, however, evaporative demand significantly affected the critical values of volumetric soil water content and soil suction for the loamy clay and clay loam only. Therefore, for saving water, different strategies are needed for these three soils.
    Agricultural Water Management 02/2011; 98(4):569-576. DOI:10.1016/j.agwat.2010.10.015 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hyperaccumulation of nickel (Ni) in certain plants may play a role in drought resistance under water stress. This article tests the influence of water stress on the Ni-hyperaccumulating shrub Hybanthus floribundus Lindl. F.Muell. subsp. floribundus. Plants grown in 1000 mg kg−1 Ni-amended Clastic Rudosol were exposed to five levels of soil water potentials (−33 [field capacity], −60, −400, −600, and −1000 kPa) for 12 wk. Water stress did not induce significant changes in growth rate, relative water content, rates of gas exchange, or carbon isotope discrimination. Water use efficiency (WUE) values were approximately threefold lower in plants at water potentials <−400 kPa than they were in those at water potentials of −33 kPa. Low WUE values suggest that this species possesses an efficient water conservation mechanism that enables its survival in competitive water-limited environments. A 38% decline in water potential and a 68% decline in osmotic potential occurred between −1000- and −33-kPa water potentials ( ), indicating that osmotic adjustment (OA) may have provided turgor maintenance in response to increasing water stress. However, Ni concentration in plants did not significantly increase in response to decreasing water potentials and is therefore unlikely to play a role in OA.
    International Journal of Plant Sciences 03/2011; 172(3):315-322. DOI:10.1086/658154 · 1.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Agriculture is sub-Saharan Africa’s largest area of economic activity, yet food insecurity and malnutrition continues to worsen. In order to overcome the unique problems facing Africa there is need for a paradigm shift in the food production and consumption patterns. The objective of the paper is to examine the current status and future prospects of good agricultural practices for underutilized vegetables in sub-Saharan Africa. Good agricultural practices are a collection of principles to apply for on-farm production and post-production processes, resulting in safe and healthy food and non-food agricultural products, while taking into account economical, social and environmental sustainability. It focuses on economically and efficiently producing sufficient, safe and nutritious food; sustaining and enhancing natural resources; maintaining viable farming enterprises, and thereby contributing to improved and sustainable livelihoods. Some of the established GAPs include, but are not limited to, EurepGAP, FAO GAP Principles, UgaGAP, KenyaGAP and GLOBALGAP. Underutilized vegetable species have the potential to contribute to food security, nutrition and health; generate income and sustain the environment; but are currently under-exploited. Historically, underutilized vegetable species have been cultivated widely and consumed as food but several are being abandoned and are now cultivated only in limited areas. Many of such species are species indigenous to Africa which have been neglected as a result of new introduced exotic species that have replaced them due to pressure of evolving consumer preferences, lifestyles, socioeconomic realities and cultural values. They are mostly gathered from the wild or are grown by local farmers for subsistence using traditional methods. Underutilized vegetables are also known as neglected, abandoned, orphaned, underused, lost, minor, traditional or forgotten vegetable species. Some of the identified indigenous vegetables in sub-Saharan African include: Amaranthus spp., African vegetable nightshades, traditional vegetable cowpeas, jute mallow, African okra, spiderplant, and African eggplant. Currently, efforts are being made on the continent to develop good agricultural practices and promote sustainable production and utilization of the underutilized vegetables by national research organizations, international research organizations, universities, NGOs and Ministries of Agriculture and Environment. Some of the work that has been done by these organizations include: identification of priority underutilized vegetables; collection, characterization, selection of promising species; bulking, packaging and distribution of quality seed; development of technical crop production technical packages, development of recipes and products; advocacy, outreach and dissemination. The future prospect is envisaged to be a focus on the development of good agricultural practices for promising vegetables, development of an efficient seed system, breeding, conservation, commercialization, processing, value addition, and product development of underutilized vegetables in sub-Saharan Africa. It is therefore imperative to develop GAP for underutilized vegetables to fully exploit their potential and to solve the problems of hunger, malnutrition, poor health and poverty that are prevalent in sub- Saharan Africa.
    technical consultation workshop; 12/2009


Available from
May 21, 2014