Meristematic Tissues
* There are two main types of plant tissues- meristematic tissues and permanent tissues.
* The specialised region in plants where meristematic tissues are present is known as the meristem.
* There are two basic types of meristems-primary and secondary.
* Primary meristem can be further divided into apical meristem and intercalary meristem.
* Meristematic tissues undergo active cell division and play a vital role in the primary and secondary growth of a plant.
Complex Permanent Tissues
*Complex permanent tissues are a group of more than one type of cells that have a common origin and work together as a unit.
* There are two types of complex permanent tissues in plants-xylem and phloem.
* Xylem performs the function of conduction of water and minerals from roots to stem and leaves.
* Phloem transports food materials from leaves to the other parts.
* Xylem consists of four different types of cells-tracheids, vessels, xylem fibres and xylem parenchyma.
* Phloem consists of four elements – sieve tube elements, companion cells, phloem parenchyma and phloem fibres.
* Complex permanent tissues are engaged in the transportation of water, minerals, nutrients and organic substances.
Simple Permanent Tissues
* Permanent plant tissue is a group of cells, which are complete in growth and usually incapable of meristematic activity.
* Permanent tissues are of two types-simple permanent tissues and complex permanent tissues.
* Simple permanent tissues consist of cells that are similar in structure and function.
* There are three types of simple permanent tissues-parenchyma, collenchyma and sclerenchyma.
* Parenchyma performs functions such as photosynthesis, storage and secretion.
* The function of collenchymas is to provide mechanical support to the growing parts of a plant.
* The function of sclerenchyma is to provide mechanical support to plant organs.
Plant Tissue Systems
* Plant tissue systems can be classified into three types: epidermal tissue system, ground or fundamental tissue system, and vascular or conducting tissue system.
* The epidermal tissue system forms the outermost covering of the plant body.
* The ground or fundamental tissue system consists of simple tissues such as parenchyma, collenchymas and sclerenchyma.
* The vascular or conducting tissue system is composed of the xylem and phloem, which together form vascular bundles.
Anatomy of Dicot and Monocot Roots
* The tissues present inside the endodermis of the dicot root, that is, the pericycle, vascular bundles and pith, are collectively known as stele.
* Both dicot and monocot roots consist of epidermis, cortex, endodermis, pericycle, vascular bundle and pith.
* The monocot root has more xylem bundles than the dicot root. It can have as many as six xylem bundles.
* The pith of a monocot root is well developed.
* Unlike the dicot root, there is no secondary growth in the monocot root.
Anatomy of Dicot and Monocot Stems
* The stem is a plant organ that develops from the plumule of a geminating seed.
* The tissues of dicot and monocot stems are quite similar but there are some differences as well.
* The hypodermis is composed of sclerenchymatous cells in a monocot stem, and collenchymatous cells in a dicot stem.
* The monocot stem has scattered vascular bundles with a conjoint closed arrangement.
* The vascular bundles on the periphery are smaller compared to the vascular bundles in the centre.
* In a dicot stem, the arrangement of vascular bundles is conjoint and open.
Anatomy of Dicot and Monocot Leaves
* Leaves perform many crucial functions such as photosynthesis and transpiration.
* The dicot leaf has three main parts-epidermis, mesophyll and the vascular system.
* In the dicot leaf, stomata are found more in the abaxial epidermis, whereas in a monocot leaf, stomata are present on both surfaces of the epidermis.
* In a monocot leaf, mesophyll cells are not differentiated as palisade and spongy parenchyma.
* In a dicot leaf, the vascular bundles are irregularly scattered in the mesophyll, whole in a monocot leaf, they are arranged in a parallel manner.
* In the leaves of grasses, veins and cells of the upper epidermis modify themselves as large, bubble shaped colourless cells also known as bulliform cells.
Secondary Growth in Stems and Roots
* Secondary growth of a plant begins after primary growth and it leads to the formation of woody axis.
* Secondary growth takes place due to the activity o secondary meristems such as vascular cambium and cork cambium.
* The fusion of intrafascicular cambium and interfascicular cambium results in the formation of the cambial ring.
* Cambium activity which takes place in spring results in spring wood and cambium activity in autumn results in autumn wood.
* Spring and autumn wood appear as alternate concentric rings and for annual rings.
* The tissue outside the vascular cambium, which includes the secondary phloem, is known as bark.
* Secondary growth of stems and roots occurs mainly in dicots and gymnosperms, whole monocots lack secondary growth.