Light and desiccation responses of Weymouthia mollis and W. cochlearifolia, two pendulous rainforest epiphytes from Australia and New Zealand

Abstract

The two species of Weymouthia occur in temperate rainforest in south-east Australia, New Zealand and southern Chile. Weymouthia cochlearifolia forms patches on trunks and branches, but can be pendulous under suitable conditions. Weymouthia mollis is typically of 'pendant' life-form, hanging from twigs and branches in the canopy. Photosynthetic electron flow in W. cochlearifolia reached 95% saturation at 160 μmol m-2 s-1 PPFD; corresponding figures for W. mollis ranged from 176 to 307 μmol m-2 s-1 PPFD or more. Both species tolerated 30 d desiccation at -41 MPa (74% r. h.) but survived lower humidities less well; W. mollis was the more desiccation tolerant of the two. The fluorescence parameter Fv/Fm recovered rapidly on rewetting. It is suggested that the main desiderata for the pendant life-form are high and reasonably regular precipitation, some shelter from wind, and moderate (but not extreme) shade. These probably cannot be fully met around the year in deciduous forests at higher latitudes.