A Simple Classroom Demonstration of Differences in Photosynthetic Capacity Among Species

Abstract

ABSTRACTPlant species differ markedly in their maximal rates of leaf photosynthesis. These differences can be demonstrated by having plants of these contrasting species compete for CO2 in a continuously illuminated, closed system. Under those conditions, species with the lower photosynthetic capacity succumb in about 1 week. A simple system suitable for classroom demonstrations of this phenomena consists of a transparent closed box into which are placed pots or flats containing plants of the two types growing in sand. Illumination can be by any convenient light source giving a continuous illumination at an intensity of 0.05 cal cm−2 min−1 (400 to 700 nm) or about 1000 ft‐c.