How portulaca seedlings avoid their neighbours.

Portulaca oleracea L. seedlings do not develop in the direction of neighbours, even when these neighbours are small and distant. Neighbouring plants could be simulated by small rectangles of a plastic that resembled leaves in its spectral characteristics. Unlike seedlings, mature plants did not respond to objects that do not influence photosynthetic light. When light of equal intensity was received from all directions, Portulaca seedlings avoided the direction with higher far-red light. Portulaca is thus able to use spectral composition and direction of light as clues for the probability of the direction of future shade.