by Jolene Adams, ARS past president, Master Rosarian, NCNH District
THE FUNCTION OF STEMS
Cells are the basic structural and physiological units of plants. Most of a plant’s reactions occur at the cellular level. Stems contain plant tissues (meristems, xylem, phloem, etc.) that are large, organized groups of similar cells that work together to perform a specific function – in this case the transport system.
The vascular system inside the stem forms a continuous pathway from the root, through the stem, and finally to the leaves. It is through this system that water and food products move.
PARTS OF THE STEM
Cambium is the layer of actively dividing cells just beneath the skin of the cane. Cambium cells divide to form ‘transportation’ tissue. This layer is seldom more than 10 cells thick, usually averaging 5 cells. It gets damaged by rubbing or accidental nicks.
This is the system of tubules that allows nutrients to flow from the root area to the growing tips of the stems and leaves. Without a healthy phloem, you wouldn’t have a rose. All the food that the roots accumulate flows up through the phloem and into the rest of the plant.
A bit further into the stem, you find the xylem. This tissue is the principal water transport system for the rose. Water and anything that is dissolved in it moves up and down through the tissues of the xylem. Xylem and phloem together form a continuous system of vascular tissue extending throughout the plant.
THE GROWING POINT
The most actively growing part of the stem is the very tip – it is the meristem. This tip is the only part of a stem (or rootlet) that grows. And it does it by cells dividing and then the next layer dividing and then the next layer dividing, etc. If the meristem is damaged or cut off, the stem cannot grow any longer.
Stem photo, by Rich Baer