Plant Tissues: Overview

1. Plant Tissues: Overview Meristems, Simple Tissues, & Complex Tissues Many of the figures found in this presentation are from the internet site http://botit.botany.wisc.edu/images/130/ and a CD entitled “Plant Anatomy” by Richard Crang & Andrey Vassilyev published by McGraw Hill.

2. I. Meristematic Tissue Origin : Promeristem, Meristem Primer, MeristemSekunder (cambium) Location : apical, intercalar, lateral • Permanent Tissue Epidermis : silica cell, stomata, trichomata, spine, velamen, fan cells. Parenchyme: assimilation, storage, water, vascular, aerenchyme, wound covering. Supporting : collenchyme,sclerenchyme (schlerenchyme fiber, sclereid) Vascular : xylem (tracheid, vessel element), phloem (sieve tube element, companion cells) Cork : feloderm, felem

3. Specialized Tissues in Plants • Roots • Absorbs water and nutrients • Anchor plant to the ground • Hold soil in place and prevent erosion • Protect from soil bacteria • Transport water and nutrients • Provide upright support

7. Specialized Tissues in Plants • Stems • Support for the plant body • Carries nutrients throughout plant • Defense system to protect against predators and infection • Few millimeters to 100 meters

8. Specialized Tissues in Plants • Leaves • Main photosynthetic systems • Suseptable to extreme drying • Sight of oxygen/carbon dioxide intake and release

9. MERISTEMATIC TISSUE • The cells of meristematic tissue are similar in structure & have thin cellulose cell walls. • The meristematic cells may be spherical,oval,polygonal or rectangular in shape. • The meristematic cells contain few vacuoles • Cells of meristems divide continuously Occurrence-Meristematic tissues are growth tissues & are found in those regions of the plant that grow. According to their position in the plant, meristems are apical, lateral & intercalary. Function-the main function of meristematic tissue is to continuously form a number of new cells.

11. Intercalary Meristem

12. Meristematic tissues – localized regions of cell division • Apical meristems:-these are situated at the growing tip of the stems & roots. At shoot apex & root apex. It brings about the elongation of the root & stem. It results in increase in the height of the plant, which is called primary growth. • Lateral meristems-these are found beneath the bark (cork cambium) & in vascular bundles of dicot roots & stems(cambium).They occur in thin layers. Cambium is the region which is responsible for growth in thickness. It causes the organ(stem or root) to increase in diameter . This is called secondary growth. • Intercalary meristems-they are located at the base of leaves or internode,e.g., Stem of grasses & other monocots.

13. Root Apical Meristem • Root cap initials • Protoderm • Ground meristem • Procambium • Root cap

14. Lateral Meristems – secondary growth in woody plants Basswood – stem in cross section; 1, 2, 3 year old stems Basswood – root in cross section

15. PARENCHYMA Parenchyma cells are oval,round,polygonal or elongated in shape. The cell wall is thin & encloses a dense cytoplasm which contains a small nucleus & surrounds a large central vacuole. Occurrence-the parenchyma is widely distributed in stem,roots, Functions- Parenchyma maintain the shape & firmness of the plant due to its turgid cells. The main function of parenchyma is to store & assimilate food. Parenchyma serves as food storage tissue . Transport of materials occurs through cells or cell walls of parenchyma cells. Parenchyma cells are metabolically active; their intercellular air spaces allow gaseous exchange.

16. Isodiametric Parenchyma Cell containing Chromoplasts: Each red dot is a Chromoplast that Contains Carotenoids.

17. Elongate Palisade Parenchyma with Chloroplasts

18. Parenchyma from Potato with large Amyloplasts

19. Parenchyma Cells containing Amyloplasts.

20. Shoot Apical Meristem

21. PERMANENT TISSUE These tissues derived from the meristematic tissues but their cells have lost the power of division & have attained their definite forms. Permanent tissues are classified into two-simple & complex. Permanent tissue-these tissues are composed of cells which are structurally & functionally similar. They are : • Epidermis • Connective • Vascular

22. Parenchyma

23. Surface View of  Epidermis from a Leaf: Note the undulating Epidermal Cells plus the Stomata (S) and Trichomes (T).

25. COLLENCHYMA • It shows many of the features of parenchyma but is characterized by the deposition of extra cellulose at the corners of the cells. In collenchyme ,intercellular spaces are generally absent. Collenchyme cells are elongated in shape. They often contain a few chloroplasts. • Occurrence-the cells of collenchyma are located below the epidermis of dicotyledon stem & petiole. Collenchyma is absent in monocot stems,roots & leaves. • Functions- collenchyma is a mechanical tissue;it provides mechanical support & elasticity.

26. SCELERENCHYMA • Composed of dead cells and sclerenchyma are greatly thickened with deposition of lignin. The cells of sclerenchyma are closely packed without intercellular spaces. • Found in stems,roots,veins of leaves. • Functions-thesclerenchyma is mainly mechanical & protective in function. It gives strenght,rigidity,flexibility & elasticity to the plant body &,thus,enables it to withstand various strains.

27. XYLEM • Nature-xylem is a vascularXylem is composed of cells of four different types: tracheids and vessels element (bounded by thick lignified. Vessels are very long tube-like structures formed by a row of cells placed end to end. They conduct water). • Functions- • The main function of xylem is to carry water & minerals salts upward from the root to different parts of shoots. • Since walls of tracheids,vessels of xylem are lignified, they give mechanical strength to the plant body.

28. PHLOEM • Nature-Phloem is composed of following two types : 1.sieve tubes;2.companion cells; • Functions-phloem transport photosynthetically prepared food materials from the leaves to the storage organs & later from storage organs to the growing regions of the plant body.

29. Collenchyma

30. Sclerenchyma SCLERIDS FIBERS Right-hand illustration modified from: Weier, Stocking & Barbour, 1974, Botany: An Introduction to Plant Biology, 5th Ed.

31. Epidermis – stoma, trichomes, & root hairs http://www.ucd.ie/botany/Steer/hair/roothairs.html

32. Xylem

33. Phloem

34. Vascular Bundles with xylem & phloem Maize or Corn – vein in cross section Alfalfa – vein in cross section

35. Periderm – cork & parenchyma TWIG WITH LENTICELS

36. Secretory Structures • nectar (flowers) from nectaries • oils (peanuts, oranges, citrus) from accumulation of glands and elaioplasts. • resins (conifers) from resin canals • lacticifers (e.g., latex - milkweed, rubber plants, opium poppy) • hydathodes (openings for secretion of water) • digestive glands of carnivorous plants (enzymes) • salt glands that shed salt (especial in plants adapted to environments laden with salt).