Studies in Translocation III. The Cytophysiology of the Phloem of Cucurbita Pepo

Abstract

The phloem of Oucurbita pepo (Duchesne) consists of respiratorily inert conduit·like sieve tubes of low resistivity to flow, respiratorily active companion cells, possibly specialized for secretion or absorption, and highly vacuolated paren· chyma. The sieve pores are open and slime not cytoplasm is present in the lumen. This division of function is interpreted as evidence for the mass flow theory.