Definition: A depression caused by erosion by water or ice. Low-lying land bordered by higher ground; especially elongate, relatively large gently sloping depressions of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet.
Definition: the biochemical pathway a plant uses to gain carbon for growth and reproduction. Plants have evolved three photosynthetic pathways, each in response to distinct environmental conditions, resulting in differences in their ecological patterns of growth and distribution.
Definition: one of three metabolic pathways for carbon fixation in photosynthesis, along with C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into 3-phosphoglycerate through the following reaction:\r\n\r\nCO2 + H2O + RuBP → (2) 3-phosphoglycerate\r\n\r\nThis reaction occurs in all plants as the first step of the Calvin–Benson cycle.