A COMPARATIVE-ANALYSIS OF THE INFLUENCE OF LIGHT ON GROWTH OF YOUNG TOMATO AND CARNATION PLANTS

Growth analyses were carried out with young tomato and carnation plants growing in a greenhouse at different mean daily light integrals. Different light integrals were created by shading, the use of additional light and by growing the plants in different seasons. Net assimilation rates (NAR) were similar for tomato and carnation. Measurements of photosynthesis confirmed the similarity between the two species in photosynthetic activity. In contrast, relative growth rate (RGR) was higher for tomato, due to a higher leaf area ratio (LAR). For both species the reciprocal of LAR was linearly related to NAR. Sensitivities of NAR and RGR to light integral, and of LAR to NAR were calculated. The sensitivity of NAR was similar for tomato and carnation and decreased with increasing light integral. The sensitivity of LAR to NAR increased with increasing levels of NAR and was considerably higher for tomato than for carnation. As a result, the growth rate of young carnation plants was more closely related to the level of mean daily light integral than that of young tomato plants. It is concluded that for the tomato and carnation species, which have quite different growth rates, similar models can be used to describe growth. The parameters however, are strongly species-dependent.