Plant stems and root

Botani

Plant stem

STEMS

• Stems are structures which support buds and leaves and serve as conduits for carrying water, minerals, and sugars.

• The three major internal parts of a stem are the xylem, phloem, and cambium. The xylem and phloem are the major components of a plant’s vascular system.

FUNGSI BATANG

1. Stem support (pendukung posisi daun, bunga,

dan buah)

2. Stem conduct (penghantar / pengangkut)

3. Stem produce new living tissue (tumbuh dan berkembang)

Development of Tissues of the Primary Plant Body of a Woody Stem

The diagram below shows the positions of these two populations of cells in a stem with only primary growth.

Primary development:

Protoderm --- Epidermis

• Apical Cortex meristem Ground

PithPhloem

Procambium Vascular cambium--- produced secnd.X & Ph

Xylem

PERTUMBUHAN PRIMER1. Batang dapat

meneruskan pertumbuhan memanjang tanpa batas, baik sebagai

1. Batang horisontal di atas tanah

2. Batang menjalar sepanjang permukaan tanah

2. Pertumbuhan jaringan primer batang pendek

• Umbi – umbian• Corm

the primary growth in cross section of a young Tilia (basswood) stem.

Secondary Growth Lateral Meristems add girth by producingsecondary vascular tissue and periderm • Secondary Plant Body - tissue produced

mersitems involved in secondary growth • Vascular Cambium - secondary growth

meristem which produces xylem and phloem • Cork Cambium - secondary growth meristem

which produces cork, a tough substance that replaces the epidermis

Secondary Growth

Secondary growth is produced by a cambium. It occurs in rows or ranks of cork, secondary xylem or secondary phloem cells. Cork cells (produced by a cork cambium) are technically part of the epidermis, and contribute to the bark of woody stems.

Dicot secondary growth occurs by growth of vascular cambium, to complete a full vascular cylinder around the plant. Secondary xylem is produced to the inside of the vascular cambium, secondary phloem to the outside. The living parts of the woody plant are next to the vascular cambium.

Formation of complete cylinder of vascular cambium

Fig. Diagram as seen in radial section, showing stages in defferentiation of vascular cambium cells

Stem structure

Flax stem cross-section, showing locations of underlying tissues. Ep = epidermis; C = cortex; BF = bast fibres; P = phloem; X = xylem; Pi = pith

A cross section of the stem of basswood (Tilia americana) showing pith, numerous rays, and three distinct annual rings. The large spring xylem cells are vessels

Modified Stems

Stem ModificationsThornsSpinesPrickles

Modified Stems

Thorn

Prickle Spine

ROOT

The root is a specialised organ that functions to:

• absorb water, mineral nutrients and in some cases oxygen

• anchor the plant in the soil substrate

• The root system makes up between 25% and 60% of the total plant body.

The root is composed of three concentric circles of primary tissues

• The central core is Vascular Tissue. This central core of cells is derived from the Procambium and is called the Stele.

• This is surrounded by a ring of Ground Tissue (Cortex).

• The Epidermis is the outer most ring of tissue.

Fig. Two views of the structure of the root and root meristem

Root System• A fibrous root system (sometimes also called adventitious root

system) is the opposite of a taproot system. It is usually formed by thin, moderately branching roots growing from the stem.

• Most trees begin life with a taproot, but after one to a few years change to a wide-spreading fibrous root system with mainly horizontal surface roots and only a few vertical, deep anchoring roots.

• A plant's taproot is a straight tapering root that grows vertically down. It forms a center from which other roots sprout.

• Plants with taproots are difficult to transplan

Roots

• Tap• Fibrous• Bulb

Fibrous rootFibrous rootTaproot

Roots

Tap RootTuberous Root

Fibrous Root