Modified stems

A modified stem is an organ that stores food, which the plant can then use to survive its dormancy period. Also, it is often the means by which a plant can spread and produce new plants.

To be classed amongst this group a modified stem must exhibit all the characteristics of a stem. It must have a stem structure: that is it will have an apical growing point; the stem itself will carry leaves with buds in their axils; and the arrangement of the leaves will be spiral, alternate or opposite each other.

Apical bud

Apical bud

Specialized Stems Like Stolons

The stem is modified from the normal in that it may not necessarily be above ground, it often grows more or less horizontally, and it usually acts as a food storage organ.

There are basically only six kinds of modified stem, all with distinct habits and growth patterns. These are tubers, rhizomes, corms, bulbs, offsets and runners. They should not be confused with modified root systems, which do not possess all the features associated with a stem.

A tuber, for example, has "eyes", which have a cluster of buds and a leaf scar. These are the nodes of a typical stem. They are arranged in a spiral, alternately or opposite each other beginning from the apical bud on the end opposite the scar where the tuber was attached to the parent plant.

Node with lateral buds

Internode

Apical bud

Root

A rhizome is a specialized stem that grows horizontally just below the ground or on the surface. The stem appears segmented as it is composed of nodes and internodes, the leaves and flower bud developing from apical or lateral buds on the stem. Roots and a lateral shoot also grow from these points.

Node with lateral buds

Internode

Apical bud

Root

Nodes And Internodes PotatoStrawberry Scale Leaves

A corm is the swollen base of a solid stem which is surrounded by scale leaves. These are attached to the stem at distinct nodes which have a bud in each axil. At the apex of the corm is a bud that will develop into the leaves and the flowering shoot.

An offset is a lateral shoot that develops from a leaf axil at the crown of a plant. This lateral shoot usually has only one bud, which develops into a plantlet with its own root and growing point.

Apical shoot Internode

Apical shoot Internode

Root

Crown Modified Stem

Root

A bulb, on the other hand, has a short, fleshy, usually vertical stem which, at its apex, has a growing point enclosed by thick, fleshy scale leaves. New bulbs develop in the axil of these scale leaves. The flower bud and foliage leaves grow up from the centre of the bulb.

A runner also develops from the leaf axil at the crown of a plant. It grows horizontally and, at several of its nodes, forms new plantlets from the lateral buds. These new plants will develop a flowering point and also send out their own runners once they have established themselves.

Crown Modified StemStolon Internode

Node _ Internode

Frequently, modified stems are referred to as stolons, but this term has purposely been avoided in this book as it has a multiplicity of meanings.

Node _ Internode

Frequently, modified stems are referred to as stolons, but this term has purposely been avoided in this book as it has a multiplicity of meanings.

The name "tuber" in horticultural terms has been much misused and has on occasions covered almost any swollen food storage organ that is chiefly underground.

A tuber is, in fact, a swollen underground stem, modified as a food storage organ. It often is of roundish (usually terminating) growth and is normally annual. The leaves are scaly and membranous, and the axillary buds provide the following year's shoots.

Within these limitations the number of plants producing true tubers is not very great. The commonest is the potato. Those plants, such as Jerusalem artichokes, that produce opposite ratherthan spirally arranged buds, such as potatoes, often have a knobbly shape. Some water lilies (Nymphaea sp.) produce small tuber-like structures that ^develop from the main rootstock towards the end of the growing season. ,

Although potatoes are prolific producers of tubers, this is unusual. Normally, plants that develop tubers do so only in very small numbers.

TUBERCLES

TUBERCLES

Modified Stems

Just a few plants produce very small tubers from the axillary buds. These buds modify into tubers and eventually fall off the parent stem.

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Any increase in numbers must be achieved artificially. As the tuber is normally an organ that allows a plant to survive its dormant period, the season to propagate tubers by artificial division should be just before growth would commence in the spring.

Cut the tuber with a sharp knife so that each piece has at least one good dominant bud or "eye". Then dust all the cut surfaces with a fungicide such as Captan to reduce the possibility of fungal infection. Stand the pieces on a wire tray and keep in a warm (21°C/70°F), dry environment, for example an airing cupboard, for a couple of days. A protective corky layer, which enhances their survival, will then develop. These tuber "seeds" should not be kept in the dry for any longer than necessary, otherwise the tuber itself will desiccate.

Therefore plant them out immediately in a hole twice their depth. They will then quickly produce roots and shoots and establish as a new plant. Label them clearly at all stages of propagation.

POTATOES

POTATOES

Potao Tuber Where Formed

A potato tuber is marked by a scar at one end, where it was attached to the parent plant, and by "eyes", or nodes, placed spirally over its surface.

1 Cut a tuber into pieces with a sharp knife. Ensure each piece has at least one good "eye".

2 Dust all the cut surfaces with a fungicidal powder. Stand on a wire tray in a warm (21°C/70°F), dry place.

3 Plant the tuber pieces in the open ground as soon as a protective corky layer has formed. Label them clearly.

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Responses

  • Ines Calabrese
    Is a node a modified stem?
    8 years ago
  • belba diggle
    How to plant nymphaea sp tubers?
    7 years ago
  • taneli
    What is the apical growing point of stem?
    7 years ago
  • Mantissa
    Is a tuber a modified stem?
    7 years ago
  • Pamphila
    What are the features of a modified stem in an organ?
    7 years ago
  • Archie
    What is stem modification stolon?
    7 years ago
  • matias
    What features do modified stems have?
    6 years ago
  • Alexa
    Is a tomato a modified stem or modified root?
    6 years ago
  • satu
    What is the meaning of modified stems?
    6 years ago
  • ella
    Is a growing tomato a modified stem of a plant?
    6 years ago
  • fearne
    What is tge term for a fleshy stem that grows horizontally below ground?
    6 years ago
  • Linda
    What is the name of the plant which has stem with distinct solid nodes and hollow internodes?
    6 years ago
  • Sara
    How to plant bulbs and modified stems?
    5 years ago
  • shukornia amanuel
    Which crop plant has a stem modified for food storage?
    5 years ago
  • sesuna
    Which plant science have lateral bud apex leaf scars?
    4 years ago
  • amanuel
    What is a crown modified stem?
    2 years ago
  • RYAN
    What is a modified stem in horticulture?
    7 months ago

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