Fresh matter is roughly composed of 85% of water that comes from the soil and 15% structural dry matter that comes from leaf photosynthesis. Sugars (CH2O) derived from photosynthesis have several roles. They may be used for plant structure construction when included in cell walls or they may be stored as reserve or even another part, used as energy for the plant's general functioning (respiration). Less than 5% of the fresh weight comes from nutrients (N, K, P, etc.) contained in the sap and as component of dry matter, so they are not considered as a relevant component of the plant architecture; their roles are entirely devoted to plant functioning (mainly enzymes).
Dry matter consists mainly of carbohydrates, lignins, oils/fats, organic acids, and proteins, and primarily originates from sugars produced via the photosynthetic process. Dry matter is obtained once the water is extracted from the fresh organs. As extremes, dry matter may be 95% of the fresh one for seeds and 3.5% for a cucumber fruit, but plant dry matter content ratio is generally about 15% of the fresh weight and in this article it is assumed that the ratio of dry weight to fresh weight remains constant.
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