Anatomy of Flowering Plants

Heartwood differs from sapwood in having dead and non-conducting elements.

In old trees, the inner region that comprises dead elements with highly lignified walls is called heartwood.

Heartwood does not conduct water but gives mechanical support to the stem.

On the other hand, the peripheral region, which is lighter in colour is called sapwood.

It is involved in the conduction of water and minerals from root to leaf.

Tracheids are chief water conducting elements of xylem in gymnosperms.

They are devoid of protoplasm and hence dead.

The wall constituting the tracheids is hard, thick and lignified.

These are elongated cells with tapering ends.

Meristem is classified on the basis of position in plant bodies into lateral meristem, apical meristem and intercalary meristem.

Lateral meristem is present on the lateral sides, e.g., vascular cambium (fascicular and interfascicular cambium) and cork cambium (phellogen).

Palisade parenchyma is absent in leaves of Sorghum.

It is a monocot plant where the parenchyma tissues of the leaves are not differentiated into palisade and spongy

In barley stem, vascular bundles are closed and scattered.

They are open only for a hours in the day time and never open at night. e.g Cereals.

The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is maturing.

Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by position of protoxylem.

In dicot root the protoxylem is located near the periphery of the vascular cylinder while in dicot stem the protoxylem is located near the centre of vascular bundle i.e. the xylem is endarch.

Vascular tissues in flowering plants develop from plerome.

Plerome is a central core of primary meristem which gives rise to all cells of the stele from the pericycle inward.

The length of different internodes in a culm of sugarcane is variable because of intercalary meristem.

Intercalary meristem is not a part of apical meristem.

It occurs in the internodes of grasses (sugarcane) between leaf nodes and enables longitudinal growth of the stem.

Endodermis is a single layered structure which separates cortex from stele.

There are both thick walled and thin walled cells in the endodermis.

The thin walled cells are known as passage cells or transfusion cells which are opposite the protoxylem groups.

These cells help in rapid transport of water from cortex to pericycle.