The biology of the crustose lichen <Emphasis Type=Italic>Rhizocarpon geographicum</Emphasis>

The crustose lichen Rhizocarpon geographicum (L.) DC. comprises yellow-green lichenized areolae which develop and grow on the surface of a non-lichenized fungal hypothallus, the latter extending beyond the edge of the areolae to form a marginal ring. The hypothallus advances very slowly and the considerable longevity of R. geographicum, especially in Arctic and Alpine environments, has been exploited by geologists in dating the exposure age of rock surfaces (lichenometry). This review explores various aspects of the biology of R. geographicum including: (1) structure and symbionts, (2) lichenization, (3) development of areolae, (4) radial growth rates (RaGR), (5) growth physiology, (6) changes in RaGR with thallus size (growth rate-size curve), (7) maturity and senescence, and (8) aspects of ecology. Lichenization occurs when fungal hyphae become associated with a compatible species of the alga Trebouxia, commonly found free-living on the substratum. Similarly, ‘primary’ areolae develop from free-living algal cells trapped by the advancing hypothallus. The shape of the growth rate-size curve of R. geographicum is controversial but may exhibit a phase of decreasing growth in larger thalli. Low rates of translocation of carbohydrate to the hypothallus together with allocation for stress resistance results in very slow RaGR, a low demand for nutrients, hence, the ability of R. geographicum to colonize more extreme environments. Several aspects of the biology of R. geographicum have implications for lichenometry including early development, mortality rates, the shape of the growth-rate size curve, and competition.     

Production,characteristics and applications of the cell-bound phytase of <Emphasis Type=Italic>Pichia anomala</Emphasis>

Among several yeasts isolated from dried flowers of Woodfordia fruticosa, Pichia anomala produced a high titre of cell-bound phytase. The optimization of fermentation variables led to formulation of media and selection of cultural variables that supported enhanced phytase production. The enzyme productivity was very high in fed batch fermentation in air-lift fermentor as compared to that in stirred tank fermentor. Amelioration in the cell-bound phytase activity was observed when yeast cells were permeabilized with Triton-X-100. The enzyme is thermostable and acid stable with broad substrate specificity, the characteristics that are desirable for enzymes to be used in the animal feed industry. The phytase-encoding gene was cloned and sequenced. The 3D structure of the enzyme was proposed by comparative modeling using phytase of Debaryomyces occidentalis (50% sequence identity) as template. When broiler chicks, and fresh water and marine fishes were fed with the feed supplemented with yeast biomass containing phytase, improvement in growth and phosphorus retention, and decrease in the excretion of phosphorus in the faeces were recorded. The cell-bound phytase of P. anomala could effectively dephytinize wheat flour and soymilk.     

Seed production of cut-leaved teasel (<Emphasis Type=Italic>Dipsacus laciniatus</Emphasis>) in central Missouri

Cut-leaved teasel is an invasive weed in Missouri that reduces the diversification of native species along roadsides and impairs traffic visibility. Teasel is a biennial and grows as a rosette in the first year and flowers the second year. Reproduction is only by seed. Field studies were conducted in 2004 and 2005 at two locations to assess the seed production of cut-leaved teasel. From a natural stand, fifteen plants were tagged at the onset of flowering. Selected plants included those considered growing in a group and those growing alone; a plant was considered alone when no other plant was adjacent for at least 60 cm. Whenever a seedhead completed flowering, it was covered with a cellophane bag and harvested one month later. Linear regression was used to correlate the weight of seeds from a single seedhead and number of seeds to estimate the total seed production per seedhead. The number of seedheads per plant varied from 3 to 56. On average, plants growing alone had 64% more seedheads per plant than plants occurring in a group. Seed numbers in the primary seedhead ranged from 511 to 1,487. Total seed production per plant ranged from 1,309 to 33,527. Seed production was 61% greater for plants growing alone versus those growing in a group and was more prolific in 2005 than in 2004. In addition, seed production per plant varied between locations for plants growing alone, but seed yield per plant was similar for plants growing in groups. Colonization of teasel in new areas is facilitated by higher seedhead numbers per plant and total seed production compared to reproduction of plants in areas of intraspecific competition.     

Tropical Vine Growth and the Effects on Forest Succession: A Review of the Ecology and Management of Tropical Climbing Plants

The climbing habit has evolved independently in many plant taxa, offering vines the ability to compete with non-climbing vegetation for resources such as light, nutrients, and water. This review examines the structural and functional characteristics that allow climbing plants to (1) achieve widespread dispersal, (2) transport large amounts of water throughout vessels, (3) maintain high photosynthesis levels through a large leaf area to biomass ratio, (4) achieve rapid vertical and horizontal expansion by fast growth rates and various climbing mechanisms and (5) survive and recover from disturbances. Due to the competitive effects of vines on trees, management of vine growth is used to preserve tropical timber plantations, combat invasive weeds, and promote rainforest recovery. In order to sustainably manage the vines into the future, it is necessary to understand the mechanisms by which they can alter tropical forest succession and the impacts of various management techniques.