Transitions Annual-Perennial Transitions Leaf Area and Allocation Total leaf area has significant effects on plant water loss. As plants grow they increase their leaf area and consequently their water use. If plants would have the same allocation programs, the size of a plant would be the only determinant of leaf area and species effects on leaf area would be negligible. But this is not the case, because plant species show a large variation in their allocation of carbon to leaves, stems, and roots. Also the amount of carbon required to built a unit of leaf area, or specific leaf area , varies across species.
Extreme examples are annual crops and their weeds and desert shrubs.
Under the same optimum conditions seedlings of a desert plants like Atriplex sp. After a net uptake of 1 kg of carbon, wheat plants will produce 20 m 2 of leaf area while Atriplex plants will produce only 2m 2 .