Transport in a marrow stem. Unlike humans and animals, plants use separate systems to transport food and water – the heavily reinforced xylem for water, and the phloem system, with its own built-in filters (sieve plates), for food. In this longitudinal section of part of a marrow (Cucurbita) stem, the red bands show the reinforcing structures in the xylem, and the lighter brown vertical bands across the vessels at the top of the image show the sieve plates arranged at intervals along the phloem.
Light micrograph by Spike Walker.
B0006199