primary phloem protophloem PO_GIT:433 A portion of primary phloem (PO:0006075) tissue has as parts the first-formed sieve elements (PO:0025406) at a particular location and does not have companion cells (PO:0000071, in angiosperms) or albuminous cells (PO:0025412, in gymnosperms) associated with the sieve elements. Protophloem is the first primary phloem to develop in any particular location in a portion of vascular tissue (PO:0009015). Sieve elements in the protophloem are smaller than in the metaphloem (PO:0006076). The protophloem usually only lasts a short time before it is replaced by metaphloem. 原生師部 (Japanese, exact) plant_anatomy PO:0006077 portion of protophloem tissue (exact) protofloema (Spanish, exact)