Cause and effect of differences in specific leaf area

The cause for differences in specific leaf area (SLA) and its effect on photosynthesis and relative growth rate (RGR) are discussed. Differences in SLA cannot, in all cases, be explained in terms of maximized photosynthetic function alone. SLA and its relation with photosynthesis are probably the result of trade-offs between different functions of the leaf, such as photosynthesis, competition, storage, damage prevention and support. Analysis of genetic variation in SLA in Plantago major was made, and the significance of this difference was evaluated in terms of photosynthetic function and protection against trampling stress. An increased ratio of leaf dry weight to fresh weight and differences in the chemical composition of the leaf dry weight caused a lower SLA, a higher protein content per unit leaf area, a higher photosynthetic capacity per unit leaf area, but a lower activity per unit leaf dry weight, and a lower RGR. Increased amounts of cell wall material per unit leaf could be related to a higher tolerance against trampling stress, but the simultaneous increase in photosynthetic capacity was only beneficial at very high photon flux densities. -from Author