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Studies were conducted on three herbaceous plant species growing in naturally high solar UV environments in the subalpine of Mauna Kea, Hawaii, USA, to determine if diurnal changes in epidermal UV transmittance (TUV) occur in these species, and to test whether manipulation of the solar radiation regime could alter these diurnal patterns. Additional field studies were conducted at Logan, Utah, USA, to determine if solar UV was causing diurnal TUV changes and to evaluate the relationship between diurnal changes in TUV and UV-absorbing pigments. Under clear skies, TUV, as measured with a UV-A-pulse amplitude modulation fluorometer for leaves of Verbascum thapsus and Oenothera stricta growing in native soils and Vicia faba growing in pots, was highest at predawn and sunset and lowest at midday. These patterns in TUV closely tracked diurnal changes in solar radiation and were the result of correlated changes in fluorescence induced by UV-A and blue radiation but not photochemical efficiency (Fv/Fm) or initial fluorescence yield (Fo). The magnitude of the midday reduction in TUV was greater for young leaves than for older leaves of Verbascum. Imposition of artificial shade eliminated the diurnal changes in TUV in Verbascum, but reduction in solar UV had no effect on diurnal TUV changes in Vicia. In Vicia, the diurnal changes in TUV occurred without detectable changes in the concentration of whole-leaf UV-absorbing compounds. Results suggest that plants actively control diurnal changes in UV shielding, and these changes occur in response to signals other than solar UV; however, the underlying mechanisms responsible for rapid changes in TUV remain unclear. [ABSTRACT FROM AUTHOR]

Examines the composition of understory wood vegetation in Plateau live oak clusters in relation to cardinal direction at upland savannas of the Edwards Plateau in central Texas. Discussion on spatial asymmetry in the woody plant community; Species composition of the woody understory community; Implications for the study of mechanism of facilitation in woody clusters.

It has been estimated that deregulation of US S&Ls will cost the US taxpayer $500bn in terms of the compensation paid out for the resulting scandals and failures. In contrast, the deregulation of UK building societies, "although initially followed by a series of scandals and losses of $1bn., eventually resulted in substantially increased profitability. The social effects in the UK have been quite different to those in the US. As a result of the increased importance placed on profitability as opposed to mutuality, many homeowners have had their properties repossessed, and investors been mis-sold unsuitable investments. However, UK building societies, by a mixture of good luck and judgement, have avoided the principal regulatory pitfalls, which beset the S&Ls in terms of bankruptcies and fraud. This paper seeks to explain these different post-deregulation experiences. It extends to the UK the looting model of Akerlof and Romer (1993) and the managerial diversion model of Nichols (1972) which went so far to explain and anticipate, respectively, the US experience. [ABSTRACT FROM AUTHOR]