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Chapter 2. STRUCTURE OF HIGHER PLANTS. Gymnosperms and angiosperms. Gymnosperms have “naked seed” Most gymnosperms are narrow-leaved evergreen trees like pines, spruces and firs http://nature.snr.uvm.edu/www/mac/plant-id/gymnosperms/gymnosperms.html
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Chapter 2 STRUCTURE OF HIGHER PLANTS
Gymnosperms and angiosperms • Gymnosperms have “naked seed” • Most gymnosperms are narrow-leaved evergreen trees like pines, spruces and firs • http://nature.snr.uvm.edu/www/mac/plant-id/gymnosperms/gymnosperms.html • Angiosperms have seeds enclosed within an ovary • Most angiosperms are broad-leaved flowering plants
Monocots and dicots • Monocots or monocotyledonous plants have an embryo with only one seed leaf. • Other characteristics of monocots are: • 1) Parallel veins • 2) Diffuse vascular bundles • 3) Flower parts usually in multiples of three.
Dicots • Dicots or dicotyledonous plants have embryos with 2 seed leaves. • Other characteristics of dicots are: • 1) Leaves have net shaped venation • 2) Vascular bundles are distributed around a central vascular cambium • 3) Flower parts are usually in multiples of four or five
From:http://www2.cdepot.net/~walser/worldofscience/Biology/Pictorial%20Help/Botany/monocots_dicots.htmFrom:http://www2.cdepot.net/~walser/worldofscience/Biology/Pictorial%20Help/Botany/monocots_dicots.htm
From: http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookPLANTANATII.html
Major parts of the plant cell • The protoplast includes: • plasma membrane • the cytoplasm • the nucleus • the vacuole • Plasma membrane = plasmalemma • a double membrane, actually a lipid bilayer, surrounding the cytoplasm and cell organelles.
Major parts of the plant cell • The cytoplasm = thick liquid within the plasmalemma containing endoplasmic reticulum and plastids of various types. • The endoplasmic reticulum = membranes where proteins are synthesized on ribosomes.
Major parts of the plant cell • Plastids = capsule-like organelles bound by a double membrane. • Plastid types: • Chromoplasts - contain pigments like chlorophyll (chloroplasts) and several others. • Leucoplasts - colorless and serve as storage bodies for oil, starch and proteins.
Major parts of the plant cell • Mitochondria - smaller than plastids, double membrane bound. • “Powerhouse” of the cell - involved in respiration and ATP production. • ATP-an energy rich compound. • Mitochondria -also involved in protein synthesis.
Major parts of the plant cell • The nucleus =the organelle which contains chromosomes; long lengths of DNA containing the genetic code. • Vacuoles - surrounded by a membrane called the tonoplast. • Vacuoles serve as storage for the cell. • Vacuoles also regulate turgor (keep cells “inflated”)
Major parts of the plant cell • The primary cell wall - composed mainly of cellulose, pectic substances and lingins. • provides protection for the protoplast and structure for the plant. • The middle lamella -lies between adjacent cells holding them together. • The secondary cell wall - lies inside the primary wall and is composed of cellulose, lignins, suberins and cutins.
Major parts of the plant cell • Plasmodesmata - strands of cytoplasmic tissue connecting individual cells to each other. • http://www.cellsalive.com/cells/plntcell.htm • http://koning.ecsu.ctstateu.edu/cell/cell.html
Plant tissues • Plant tissues = large tracts of organized cells of similar structure that perform a collective function. • Meristematic tissue or meristem = actively dividing cells which can differentiate into other tissues and organs. • Permanent tissues= fully differentiated tissues developed from meristems.
Meristematic Tissues • Apical meristems: • 1) shoot apical meristems- • Determine leaf patterns and branching habit - opposite, alternate, spiral • Produce primary vascular tissues and stem tissue • May produce terminal flowers or remain vegetative and continue to grow producing flowers on lateral growth depending on the plant
Meristematic Tissues • 2) root meristems- • Found at the root tips • Some plants have a dominant taproot which develops mainly downward with little lateral growth. • Examples include: carrots, beets, oaks and pecans.
Meristematic Tissues • Many plants lack a strong tap root and so they develop a well branched fibrous root system. • Grasses, grains and shallow rooted trees are examples. • http://koning.ecsu.ctstateu.edu/Plant_Biology/meristems.html
Subapical meristems • Subapical meristem -produces new cells a few millimeters behind an active apical meristem. Cells also expand in this area increasing internode length. • Plants that bolt like mustard, and lettuce do so because of the activity of the subapical meristem.
Intercalary meristems • Intercalary meristems = meristems separated from other meristematic tissues by older more mature or developed tissue. • Intercalary meristems are located just above the leaf sheath of grasses and many other monocots.
Lateral meristems • Lateral meristems = cylinders of actively dividing cells somewhat below the apical or subapical meristem continuing through the plant axis and producing secondary growth. • May be referred to as vascular cambium • produces new xylem and phloem tissue; • the cork cambium produces mainly bark.
Lateral meristems • The continued increase in diameter of trees and other woody perennials -> lateral meristems. • The “growth rings” that are produced in woody plants which allow determination of plant age are created by this lateral growth.
Woody Stem Cross Section Insert drawing from page 21 :
Permanent tissues • Simple tissues = permanent tissue composed of only one cell type. • Examples : epidermis, collenchyma, parenchyma, sclerenchyma and cork. • Complex tissues -composed of of more than one cell type. • Examples are xylem and phloem.
Simple tissues • The epidermis = single exterior layer of cells that protects plant parts. • The epidermis is often covered with cutin, a waxy substance that prevents water loss. • Parenchyma tissue -made of living thin walled cells with large vacuoles and flattened sides. • Parenchyma cells retain the ability to become meristematic and can heal wounds and regenerate other types of tissues.
Simple tissues • Sclerynchyma tissue - composed of thick walled cells found throughout the plant as fibers and sclerids. • The protoplasts in these cells die eventually. Sclerynchyma cells are common in bark, stems and nut shells. • Collenchyma tissue- gives support to young petioles, stems and veins of leaves. • Cell walls of collenchyma are thickened cells mainly made up of cellulose. • A living tissue
Simple tissues • Cork tissue occurs mainly in the bark, stems, and trunks of trees. • The cell walls are suberized (suberin is a waxy substance), and the protoplasts are short lived. • As a result cork tissue is mostly dead.
Complex tissues • Xylem = a complex tissue that conducts water and dissolved minerals in plants. • Xylem can be composed of vessels, tracheids, fibers and parenchyma. • Vessels = long tubes made up of short vessel members .
Complex tissues • Tracheids =long, tapered dead cells that conduct water through pits. • Fibers = thick walled sclerenchyma cells that provide support to plants. • Most xylem tissue is missing one or two of these cell types.
From: http://www.iacr.bbsrc.ac.uk/notebook/courses/guide/xylem.htm
Complex tissues • Phloem -a complex tissue which conducts metabolites (food) from the leaves to stems, flowers, roots and storage organs. • comprised of sieve tubes, sieve tube members, companion cells, fibers and parenchyma.
Phloem • Sieve tube members = long slender cells with porous ends called sieve plates and are found only in angiosperms. • Gymnosperms have sieve cells which are similar but lack the sieve plate. • Companion cells -closely associated with sieve tube members and aid in metabolite conduction.
Phloem • Phloem fibers - thick walled cells that provide stem support. • Parenchyma cells in the phloem serve as storage sites.
THE PLANT BODY • Roots- • conduct water and mineral nutrients • support and anchor the plant • May serve as storage organs for photosynthesized food.
THE PLANT BODY • The root cap - a layer of cells that covers the root tip and protects the procambium as the root pushes through the soil. • Cells of the root cap are continually sloughed off and replaced by new cells to keep the protective layer intact.
More roots……. • The endodermis = a single cell layer found only in the root. • Each cell in the layer is encircled by a waterproof band called the Casparian strip which does not let water and nutrients between the cells. • In order for the soil solution to get in to the xylem it must travel through the cell itself (protoplasm).
