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Uploaded byDhaneesh Ram
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Nodal anatomy, Leaf development & Phyllotaxy

The document describes nodal anatomy and phyllotaxy, explaining the structure of shoots, nodes, and leaf traces, as well as the transport of water and nutrients in plants. It details types of phyllotaxy, including alternate, opposite, and whorled arrangements of leaves, along with specific examples and subcategories for each type. The concepts emphasize the importance of leaf arrangement in relation to plant growth and development.

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NODAL ANATOMY
NODALANATOMY  Shoots consists of stems bearing leaves.  The point where the leaf attached to the stem called Node. ( site of attachment of leaves to the stem )  The distance between two nodes on the shoot is called Vegetative Internodes.
LEAF TRACES  Leaves must have access to a source of water and essential minerals.  This transport of substances takes place in primary vascular connections between the stem vascular system and the base of leaves called Leaf traces.  Leaf traces are composed of protoxylem, metaxylem, protophloem and metaphloem.
 Typically contains transfer cells in both primary xylem and primary phloem.
LEAF GAP  The continuity of the cylinder of primary vascular tissue is broken immediately above the position of outward divergence of leaf trace, leaving a discontinuity is called Leaf Gap.  Since, these leaf gaps doesn’t affect vascular system.  Lateral connectivity between tissues on top and bottom of the leaf gap is formed, since vascular system connectivity is breaked due to leaf gaps.
PHYLLOTAXY
PHYLLOTAXY  “Phyllotaxis” or “Phyllotaxy” is the arrangement of leaves on a stem.  The word phyllotaxy is derived from ancient Greek word. ( Phyllo means leaf and taxis means arrangements )  Phyllotaxy in mature plants is directly related to the position & size of leaf primordia produced on apical meristems of varying size and shape.
TYPES OF PHYLLOTAXY  Based on the number of leaves and arrangement of leaves from the nodes, the phyllotaxy has various types. I. Alternate II. Opposite III. Whorled
Alternate Phyllotaxy  When only one leaf develops at each node. Eg: Brassica campestris  Based on the position of leaves at after particular number of leaves, alternate phyllotaxy is further subdivided into two. a) Distichous b) Tristichous
A) Distichous:  When 3rd leaf comes over the first one. Eg; Grasses. B) Tristichous:  When 4th leaf comes over the first one. Eg; Cypres.
Opposite Phyllotaxy  When a pair of leaves are present just opposite to each other at each node, eg; Calotropis.  There are two types in opposite phyllotaxy. A. Opposite Deccusate B. Opposite Superposed A) Oppposite Decussate:  When two successive pairs of leaves occur at right angle to each other, eg; Psidium gujava.
B) Opposite Superposed:  When all pairs of leaves occur in same plane. Eg; Combretum.
Whorled Phyllotaxy  When more than two leaves are arranged in the form of whorl at each node, the phyllotaxy is called Whorled. Eg; Hydrilla verticillata, Nerium etc.,
Nodal anatomy, Leaf development & Phyllotaxy