• Leaves ensure light interception, and intercepted light results in biomass production through photosynthesis. The produced biomass allows the formation of new organs by the meristems and their further expansion. Thin leaf blades are optimized for efficient light captivation. Individual leaf-functioning duration is almost never indefinite. It may be short (less than 1 month for most cultivated Poaceae) or long (several years for some conifers) and may depend on environmental factors.
• Stems are basic elements of the plant structure and play a mechanical role for its stability. Produced by the functioning ofapical meristems they may branch and give rise to specific branching patterns. Their expansion in length is called primary growth and it is generally short in time; meanwhile, their expansion in diameter, also called secondary growth in trees, may be indefinite through stems or plant life span. Stems also play a functioning role in conducting the water absorbed by roots through the hydraulic plant architecture till the tips ofthe axes network. Conversely, they transport the sugars produced by the leaves through the comprehensive plant structure.
• Fruits arise from flowers, after fertilization and fruit set, and are reproductive organs. Their sink can be so big that they may drastically reduce the initiation and/or the expansion of the other organs, as in the case of sunflower. Fruits' sink duration varies with plant species.
• Roots take water and nutrients from their environment. The whole root system is here considered as a single organ whose sink lasts the entire plant growth duration.
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