Question

State two reasons why a rhizome, corm and a stem tuber are considered as stems

Answer 1

Answer:

Rhizomes, tubers, bulbs and corms are actually underground stems, not roots.  These underground stems are storage containers for the plant.

Explanation:

Rhizomes are stems that grow horizontally, but rhizomes grow underground and generally have a thickened stem that is used for storage.  Rhizomes have eyes or buds that appear along the top and sides, which grow upward to produce new stems and foliage.  Some rhizomes are fleshy like the iris and some are slender and elongated with internodes as in Bermudagrass.  To propagate, cut into sections containing at least one eye and plant.

Tubers are thickened terminal portions of the stem.  They are usually fat, round and knobby and do not grow horizontally.  They have eyes or buds that create new shoots which will become new plants.  Tubers can be cut into sections containing at least one eye per section.  Caladiums, cyclamen and tuberous begonia are all tuber plants.

A bulb actually contains the embryo of a new plant.  If a lengthwise cross section cut were made you would see a tiny stem and flower as well as fleshy modified leaves called scales encircling the embryo.  These scales serve as food reserves for the tiny plant.  There are two types of bulbs.  One is like an onion with an onion-like skin called a tunic, as in tulip.  The other has overlapping scales like garlic and no outer skin, such as lilies.  Propagate by dividing bulbils (lateral buds on the base plate) off bulb and replanting or storing until the next planting season.

Corms are similar to bulbs but do not have fleshy scales.  Corms are either rounded or slightly flattened at the top and have dry scale-like scales held together at the basal plate where the roots grow.  The parent corm dies back but produces cormels or cormlets from buds on the top or side of the original corm.  Large new corms may flower the following year, but the smaller cormels may take several years to bloom.  Cormels can be divided from the shriveled parent corm and planted separately.  Gladiolus and crocus are examples of corm plants.