Physiological ecology of photosynthesis of five sympatric species of Velloziaceae in the rupestrian fields of Serra do Cipó, Minas Gerais, Brazil

Comparative ecophysiology of photosynthesis of five sympatric Velloziaceae species (Liliidae, Monocotyledonae) in the savanna- or cerrado-like rupestrian fields of Serra do Cipó, southeastern Brazil (19°17′S; 43°33′W, 1170 m a.s.l.), was assessed by field measurements of chlorophyll fluorescence parameters on 3 consecutive days in October 2002. The species investigated co-occurred in a plot of 50 m×50 m. The chosen species were distinguished by different architectures, mainly tallness of the plants. They were Vellozia variabilis Mart. ex Shult. f.>Vellozia glabra J.C. Mikan>Vellozia nivea L.B.Sm. et Ayensu=Vellozia alata L.B.Sm.>Barbacenia involucrata L.B.Sm. In the open highly sun exposed habitat there was no photoinhibition in any of the five species being not reversible within 30 min at any time during the day including the afternoon. There was a slightly but not statistically significant better instantaneous performance of the taller species. Significant differences showing a higher intrinsic photosynthetic capacity of the taller as compared to the smaller species were revealed by photosynthetic parameters extracted from light dependence curves obtained in the morning and at midday. Light dependence curves of all five species showed a significant and substantial drop of intrinsic photosynthetic capacity when measured in the afternoon as compared to the morning and midday. As this cannot be explained by a build up of photoinhibition during the day this is a novel observation made here with the Velloziaceae.