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V stages start with VE (cotyledons above soil) and VC (hypocotyl straightened, but unifoliolate leaves not unfolded). To determine the other vegetative stages, you must count the number of nodes on the main stem. Start counting from the node at which the unifoliolate leaves are or were attached. This node and the one below it (cotyledonary node) are the only places on the soybean stem where two petiole scars are situated opposite from each other on the stem. Continue counting until you reach the uppermost node with a fully developed leaf. A fully developed leaf is one that has a leaf above it with unfolded leaflets. This is determined by observing the leaflet margins. If the leaflet edges no longer touch each other then the leaf has unfolded. Thus, a V2 plant has unfolded leaves on three nodes including two nodes where trifoliolate leaves are attached. Remember to count nodes even if the leaf at that node has fallen from the plant, and only main stem nodes are counted. |