Plant Tissue Packet #51 Chapter #35

Plants Introduction Plants are sedentary in comparison to animals Tissue, in comparison to animals, is more, or less, rigid Cells, when taken into isolation, are weak and fragile The strength of plants rise from the cell walls Cell wall Type of extracellular matrix, that the cell secrete around itself, allows “wood” to be thick and hard or thin and flexible in a leaf

Tissue An aggregation of morphologically similar cells and associated intercellular matter acting together to perform one or more specific functions.

Tissue II Plant tissue may be Complex Meristematic Embryonic Totipotent Simple Composed of one cell type Parenchyma Collenchyma Sclerenchyma Complex Composed of more than one cell type Ground Dermal Vascular Xylem Phloem

Meristematic Tissue

Meristematic Tissue Meristems are regions of undifferntiated, embryonic cells. Initially, the cells are totipotent. Meristems are present throughout the life of a plant, and are the source of seasonal new growth Height Primary Meristems Girth Secondary Meristems

Primary Meristem Primary meristem, located at the tips of roots and shoots, is responsible for an increase in the height of the plant . Apical Meristem A type of primary meristem, is responsible for increase in plant length (height). Located in two different regions of the stems and roots Apical bud Tips of roots and shoots Axillary buds Located in the leaf axils

Secondary Meristem Secondary meristem, located in the margins of the stem and root, is responsible for increase in plant girth. Vascular Cambium Give rise to secondary xylem and phloem Cork Cambium Gives rise to the periderm The outer woody layer of roots and stems.

Ground Tissue

Ground Tissue & Types of Plant Cells Ground tissue have two main functions Acts as “packing” and supportive tissue Food manufacturing and storage Ground tissue is composed of three main types of cells Parenchyma cells Collenchyma cells Sclerenchyma cells Ground Tissue Cell Types Parenchyma Cells Collenchyma Cells Sclerenchyma Cells

Parenchyma Cells Generalized, box-shaped cell with uniformly thick cell walls. These cells have a variety of functions.

Collenchyma Cells Similar to parenchyma cells except that the cell walls are further thickened with cellulose.

Sclerenchyma Cells Usually dead cells with thick lignified, and cellulose rich, secondary cell walls Two basic types Sclerids Short and unbranched cells found in seed coats and fruit Fibers Long, slender, tapered cells Jute Hemp Flax

Plant Cells

Vascular Tissue

Introduction There are two types of vascular tissue. Xylem Phloem Conducts water Phloem Conducts sugars

Vascular Tissue Xylem

Xylem Xylem conducts water and inorganic substances from the roots to the aboveground parts of the plant and out of the stomatas. It is a complex tissue composed of several cell types. Conducting cells Tracheids Vessel elements Ground cells Parenchyma Sclerenchyma fibers

Xylem Xylem is composed of four main elements. Vessel Elements Tube like structures, that have more than one perforation at each end so, that water to move easily from cell to cell. Form straw-like structures called vessels Tracheids Cells have no open ends and the pits occur in pairs so that the water can pass easily through the thin pit membrane Sclerenchyma Fibers (Cells) Long cells whose secondary walls are commonly lignified. Pits frequent Used for support Parenchyma cells Provide structural support around the conducting cells.

Components of Xylem Components of Xylem Vessels Tracheids Fibers Parenchyma

Develops from the procambium Types of Xylem There are two types of xylem Primary xylem Formed from the embryo and the resultant meristems. It is derived from the procambium. Secondary xylem Develops later and is formed during secondary thickening Produced from the cambium. Types of Xylem Primary Xylem Develops first Develops from the procambium Secondary Xylem Develops second Develops from cambium

Vascular Tissue Phloem

Phloem Phloem is the plant tissue that conduct foods made in the leaves to all other parts of the plant.

Types of Phloem Primary phloem develops from the procambium Secondary phloem develops from the vascular cambium Types of Phloem Primary Phloem Developed from procambium Secondary Phloem Developed from vascular cambium

Components of Phloem Sieve tubes Companion cells Sclerenchyma cells Highly specialized phloem cells Companion cells Form from sieve tubes early in their development Contains a nucleus where the sieve tube does not Walls between two are thin and densely pitted Sclerenchyma cells Parenchyma cells Components of Phloem Sieve Tubes Companion Cells Sclerenchyma Cells Parenchyma Cells

Overall Picture of Vascular Tissue

Dermal Tissue

Introduction Epidermis Periderm Primary outer protective, usually of one layer of cells, covering of the plant Cells of epidermis have thick primary cell walls and are covered by a special cuticle. Modified cells, of the epidermis, form hairs of various kinds and stomata Periderm Secondary epidermis Lies directly beneath the phloem. Periderm and phloem combined make up the bark of a woody plant.

Dermal Tissue II Epidermis Stomata Openings in the epidermis Regulate gas exchange in the plant Formed by two specialized epidermal cells Guard cells Regulate the diameter of the pore Distributed in species- specific pattern within each epidermis

Dermal Tissue III Epidermis Hairs Trichomes Appendages derived from epidermal cells Function in protection, absorption and secretion Cotton seed Single hair cells developing the epidermis if cotton seed Walls will be secondarily thickened with cellulose to form cotton fibers Root hairs are used to take up water and ions from the soil

Dermal Tissue IV Epidermis Botanical Terms Glaborous Hairless Pubescent Fuzzy Hirsute Hair All of the preceding terms refer to the presence or absence of trichomes

Secondary Epidermis produced by the cork cambium. Dermal Tissue IV Dermal Tissue Epidermis Stomata Trichomes Periderm Secondary Epidermis produced by the cork cambium.

Review

Plant Tissue Plant Tissue Meristematic Tissue Embryonic Tissue Totipotent Tissue Simple Tissue Parenchyma Collenchyma Sclerenchyma Complex Tissue Dermal Tissue Vascular Tissue Ground Tissue

Plant Tissue Complex Tissue Dermal Tissue Plant’s protective covering in contact with the environment Facilitates water and ion uptake in roots Regulates gas exchange in leaves and stems Vascular Tissue Xylem & phloem Conducts water and solutes between organs Provides structural support Ground Tissue Packing and supportive tissue Food manufacturing and storage