Growth-form and environment in cave-dwelling plants ofPlumaria elegans

Abstract

Plants of Plumaria elegans (Bonnem.) Schm. growing in a sea cave near to Lough Ine, Ireland, exhibit marked and progressive morphological changes the deeper they penetrate into the cave. Plants taken from deep in the cave grow to resemble those found nearer the mouth of the cave when cultured at an irradiance of 2630 μW cm-2 whereas similar plants cultured at 628 μW cm-2 show little or no change in morphology. It is concluded that these modifications are phenotypic rather than genetically induced and that light is probably the major factor influencing the morphology of the plants in the cave. Contaminating algae were introduced into the cultures probably as spores lodged in the branches of Plumaria. At the lower irradiance only four such species developed, each of which was known to occur deep in the cave. In contrast, at the higher irradiance 22 contaminating species were identified including many known only from the outer reaches of the cave or from unshaded situations. Clearly, spores of many species p...