About
24
Publications
4,803
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
881
Citations
Current institution
Publications
Publications (24)
This chapter presents case studies of four conservation sites and 11 green roofs located in the broadly coastal ecoregions of western California. Geographically complex, California’s many ecoregions are differentiated by topography and microclimate along the coast. This chapter focuses on the chaparral/shrub/meadow/and dune ecoregions from San Fran...
Plants displaying heavy metal hyper-accumulation and high biomass could be used in phytoextraction. The present study utilises photosynthetic acclimation rates and morphological measurements to gauge cadmium toxicity in radish plants raised on nutrient solutions containing 0, 5, 10 and 20 μM CdCl2. Growth rates displayed a dose-dependent decline wi...
Green roofs offer a variety of ecological benefits that include decreased storm water runoff, reduced pollutant loading of storm water, and reduced urban heat island effects. This study investigated suitable plant species for green roofs in southern California. Four treatments were
selected: plant species native to southern California, with and wit...
The fan-shaped leaves of the resurrection plant Myrothamnus flabellifolius Welw. fold during episodes of drought and consequent desiccation of the tissue. The leaf teeth of M. flabellifolius have several features characteristic of hydathodes. Tracheary elements from the three vein endings that converge in each leaf tooth subtend and extend into a c...
Sand verbenas (Abronia spp., Nyctaginaceae) are difficult to germinate in the laboratory. This hinders conservation and restoration efforts for Abronia spp. some of which are rare and others of which have been displaced from dune environments by invasive species and human activities. The possibility that ethylene (supplied as the liquid ethephon) c...
1. Root elongation as a function of soil temperature was determined for the CAM succulent Opuntia ficus-indica, under three different day/night air temperatures (15 °C/5 °C, 25 °C/15 °C and 35 °C/25 °C) and an ambient (360 μmol mol–1) vs a doubled CO2 concentration (720 μmol mol–1) at 25 °C/15 °C, the optimum temperature for net CO2 uptake.
2. Root...
Presents a jigsaw activity that encourages students to critically analyze the collected literature on a certain topic from different viewpoints. (YDS)
ABSTRACT Crassulacean acid metabolism (CAM) species show an average increase in biomass productivity of 35% in response to a doubled atmospheric CO2 concentration. Daily net CO2 uptake is similarly enhanced, reflecting in part an increase in chlorenchyma thickness and accompanied by an even greater increase in water-use efficiency. The responses of...
Of the thirty-three perennial species recorded along line transects at a site in the northwestern Sonoran Desert, nine species were succulents from different families (Cactaceae, Crassulaceae, and Agavaceae) and a further eight were from the Asteraceae. The CAM succulent Agave deserti, the C3 drought-deciduous Encelia farinosa, and the C4 bunchgras...
To help evaluate root distribution patterns, elongation rates of individual roots were measured as a function of soil temperature for Encelia farinosa (a Câ species), Pleuraphis rigida (Câ), and Agave deserti (CAM), sympatric codominants in the northwestern Donoran Desert. Measurements were made at current and doubled COâ concentrations under winte...
To help evaluate root distribution patterns, elongation rates of individual roots were measured as a function of soil temperature for Encelia farinosa (a C3 species), Pleuraphis rigida (C4), and Agave deserti (CAM), sympatric codominants in the northwestern Sonoran Desert. Measurements were made at current and doubled CO2 concentrations under winte...
The effects of constant and fluctuating substrate salinity on flag leaf photosynthesis and grain yield of wheat were investigated. Plants exposed to salinity fluctuating around a mean integrated value of 25 mol m-3 NaCl (0-50 mol m-3) and around 50 mol m-3 NaCl (25-75 mol m-3) had yields 36 and 38% higher, respectively, than those receiving the cor...
Although the disaccharide trehalose predominates in a wide variety of desiccation-tolerant lower organisms, including some lower vascular plants, it is rare in higher vascular plants. Sucrose is suggested to have an analogous role to trehalose in stabilizing the membranes of desiccation-tolerant seeds and pollen of angiosperms. In the present study...
Morphological, anatomical and ultrastructural differences between leaf tissues of field-grown and normal and hyperhydric in vitro-cultured Eucalyptus saligna were investigated. Hyperhydric material showed abnormal, often discontinuous development of the epidermis and cuticle. Stomata were malformed. The leaf lamina appeared thickened and was charac...
Possible sites of iron pumping associated with glandular salt excretion from the leaf of the mangrove Avicennia marina were investigated using energy-dispersive X-ray analysis and ATPase cytochemistry. The collecting cells of the gland had low sodium and chlorine ratios and high potassium ratios. This contrasted with the stalk/excretory cells of th...
Dormancy in seeds of Manihot glaziovii is overcome at 25C by application of ethrel at effective ethylene concentrations equal to and greater than 10 ll–1. Imbibition of seeds in ethrel broadens the temperature optimum for germination but does not prevent the development of secondary dormancy at temperatures of 35C and greater and 15C and lower. Sec...
Each salt-excreting gland of the mangrove Avicennia marina (Forsskål) Vierh. consists of two to four collecting cells, one stalk cell, and eight to twelve excretory cells. Differential membrane staining by zinc iodide-osmium tetroxide (as a post-fixative) or phosphotungstic acid (as a section-stain) was used to characterise the ultrastructure of th...
S ummary
Leaf anatomy, rates of photosynthesis, leaf N, chlorophyll, RuBP carboxylase and nitrate reductase were studied on the indigenous Agrostis magellanica Lam. and the invasive alien Agrostis stolonifera L. on Marion Island (46° 54′ S, 37° 45′ E). Leaves of A. magellanica were more deeply ridged, thicker and more sclerophyllus than those of A....
S ummary
Diurnal and long‐term excretion by leaves of Avicennia marina seedlings growing in aqueous culture was correlated with substrate salinity and transpiration. Excretion was greater in 100% than 50% seawater but the reverse was true for transpiration. The diurnal excretion pattern, with exudation minimal during the day and maximal during the...
S ummary
The salt excreting glands on both the adaxial and the abaxial surfaces of a sequential developmental series of leaves of Avicennia marina were studied at the light microscopic and ultrastructural level. Scanning electron and light microscopy have shown that there is a decrease in the total number of glands on the adaxial and abaxial surfac...
Thesis (Ph.D.- Biological Sciences)-University of Natal, Durban, 1986.
