Geophylly: Consequences forLedebouria ovatifoliain its Natural Habitat

Abstract

Geophylly is the phenomenon, exhibited by certain plants, of growing with their leaves tightly appressed to the soil surface. The plants concerned usually produce only a few broad leaves at a given time Ledebouria ovatifolia (Bak.) Jess., is such a plant and is a bulbous member of the Liliaceae growing on open spots in the grassveld of the summer rainfall area of South Africa- The spectral optical properties of the leaves, the temperatures of the leaves and the soil, transpiration rate, rate of CO2-gas exchange and microclimatic conditions were measured on a plant in its natural habitat and the energy budget was calculated. The deciduous amphistomatic leaves absorb 71% of the incident global radiation. As a result of the high energy input, the leaf temperature at noon is 10.1 K higher than the air temperature but still 7-5 K lower than the surface temperature of the bare soil. Important in the energy budget of L. ovatifolia is the high energy loss by transpiration (1.73 g dm−2 h−1) and the convective cooling by transient free-forced convection. CO2 uptake (18.2 mg dm−2 h−1) occurs only at the upper leaf surface because insufficient light penetrates the mesophyll to produce net photosynthesis near the lower leaf surface.