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.
Teak and pine are most suitable for the study of critical secondary growth because in secondary growth, secondary tissues are formed from lateral meristem which is well developed in these two cases and secondary growth occurs in gymnosperms and dicots.
In plants, conducting tissue xylem has an important integral cell as xylem vessel which is enucleate.
The phloem on other hand has a row of sieve tubes which are also enucleate at maturity.
Primary Meristems : They are those meristematic tissues which are dervied directly from the meristems of the embryo and retain their meristematic activity.
They are present at root, shoot tip and leaf primordia.
Root shows the following regions Root cap or calyptra - caplike protective covering over tip of the root Meristematic region is the subapical position Zone of elongation - receives new cells from the growing point Root hair zone - is the zone of differentiation Zone of mature cells - having thick walled impermeable cells.
The apical meristem of the root is present at all the root tips.
Apical meristem is subterminal in position of the growing root tips and responsible for terminal growth of the root in plants.
The major storage component of Avocado fruit is oil. It is stored in specialized mesocarp cells called idioblast.
