Geophylly: Consequences forLedebouria ovatifoliain its Natural Habitat

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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.

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