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Uploaded byRahul Vrushaban
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PLANT TISSUES

This document discusses the three types of meristematic tissues in plants: apical meristems, intercalary meristems, and lateral meristems. Apical meristems are located at shoot and root tips and facilitate primary growth. Dicots have apical meristems in both shoots and roots, while monocots only have them in roots. Monocots also have intercalary meristems that allow leaf regrowth. Lateral meristems cause secondary growth in dicots by increasing stem diameter. The document also describes simple and complex permanent tissues, including parenchyma, collenchyma, sclerenchyma, xylem, and phloem.

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Meristematic Tissues  Meristems are places in plants where cell division is occurring.  During cell division, one cell becomes two cells. Each new cell can also divide.
Meristematic Tissues  In this class we will discuss three kinds of meristems:  Apical Meristems  Intercalary Meristems  Lateral Meristems
Apical Meristems  In plants belonging to the DICOT class, apical meristems are located in BOTH the shoot tips and root tips. A shoot is simply a young, leaf-bearing stem.  In plants belonging to the MONOCOT class, apical meristems are located ONLY in the root tips. Microscopic View of an Apical Meristem
Apical Meristems •Primary growth of shoots and roots occurs as the cells of the apical meristem divide and elongate.
Intercalary Meristems  In addition to the apical meristems located in their root tips, plants in the MONOCOT class have special meristems called intercalary meristems.  Intercalary meristems are located on monocots where the leaf bases connect to the stem of the plant.
Intercalary Meristems Monocots, like grasses, have intercalary meristems which allow the leaves to grow back after mowing.
Lateral Meristems  In addition to the apical meristems located in the shoot and root tips, plants in the DICOT class have lateral meristems.  Lateral meristems cause SECONDARY GROWTH.  Secondary growth causes stems and roots to grow larger in diameter. Lateral Meristems cause an increase in stem diameter
Lateral Meristems Think of a lateral meristem as being a cylinder, several cell layers thick, of actively dividing cells.
Permanent Tissues Permanent tissues are of two types; Simple permanent tissue Complex permanent tissue
Simple permanent tissue  Parenchyma  store food and water  Collenchyma  provide support for plant organs  Sclerenchyma  supporting function  secondary walls impregnated with lignin  fibers and sclerids  may be nonliving at maturity
Parenchyma - are the general purpose ceIIs of plants - cells are rounded in shape & have uniformly thin walls found in all parts of the plants. - living at maturity, have large vacuoles - location Ieaf, stem (pith), roots, fruits
collenchyma  cells are elongated (up to 2mm long) with unevenly thickened walls ( thin on the sides but thick at the angles where 2 or more cells meet)  differentiate from parenchyma cells & are alive at maturity
sclerenchyma  - sclerenchyma cells which are non-living and lack protoplasts at maturity Types: 1. scIereids or stone cells 2. fibers
Complex Permanent Tissues Vascular Tissues - specialized for long-distance transport of water and dissolved substances. - contain transfer ceIIs, fibers in addition to parenchyma and conducting ceIIs - location, the veins in Ieaves  types 1. Xylem 2. phloem
Xylem  Xylem tissue conducts water and dissolved mineral nutrients.  It is composed of columns of vessel cells (tracheids in gymnosperms), stacked one upon another, and fibers.  Vessel cell walls are pitted and allow water passage between the xylem and surrounding tissues. Mature xylem cells are dead. Xylem Phloem
 Xylary elements – the conducting cells in xylem - 2 kinds of xylary elements:  tracheids – the only water conducting cells in most woody, non flowering plants.  vessel elements – occur in several groups of plants, including angiosperm. - both are elongated, dead at maturity, lignified secondary cell walls
Phloem  Phloem tissue conducts the food produced by the leaves in a downwards direction to stems and roots (from source to sink).  Phloem is composed of sieve tubes, companion cells, and fibers.  The end walls of the sieve tubes are called sieve plates. Xylem Phloem
Sieve tube elements – main conducting ceIIs of phloem - elongated and non-nucleated - uniformly thin walled with the end walls perforated to from the sieve plate. - sieve tube element are attached end to end to form the sieve tube.
PLANT TISSUES