BOTANY Higher Secondary Second Year - Textbooks Online

2. Epidermis protects the underlying tissues.
3. Stomata involve in transpiration and gaseous exchange.
4. Trichomes are also helpful in the dispersal of seeds and fruits.
5. Root hairs absorb water and mineral salts from the soil.
Vascular tissue system
The vascular tissue system consists of xylem and phloem. The elements
of xylem and phloem are always organized in groups. They are called
vascular bundles. In dicot stem, the vascular bundle consists of cambial
tissue in between xylem and phloem. Such vascular bundle is called open
vascular bundle. In monocot stem, cambium is absent in the vascular
bundle, hence it is known as closed vascular bundle
In roots, xylem and phloem are arranged in an alternate manner on
different radii. It is called radial arrangement. In stems and leaves,
xylem and phloem are arranged at the same radius and form a vascular
bundle together. Such vascular bundle is called conjoint vascular bundle.
Depending upon the mutual relationship of xylem and phloem, conjoint
vascular bundles are divided into three types. They are collateral,
bicollateral and concentric.
Open vascular
bundle
Xylem
Bicollateral
vascular bundle
Phloem
Cambium
Xylem
Phloem
Cambium
Phloem
Closed vascular
bundle
Amphicribral
vascular bundle
Fig. 2.9. Various types of vascular bundles
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Phloem
Xylem
Xylem
Radial
arrangement
Amphivasal
vascular bundle