Chapter 4: Tissues

What is the difference between primary and secondary meristems?

Meristems: tissue associated with plant growth - Found in growing regions of plant organs - Comprise dense moss of undifferentiated cells - Cells metabolically very active - Divide continuously through life of plant - Classified by origin of initiating cells 1. Primary meristems: derived from embryonic growth (promeristem) a. Formed when plants starts growing b. Give rise to primary tissues c. Produce primary growth 2. Secondary meristems: derived from permanent tissue a. Formed later, usually after primary growth b. Gives rise to secondary tissues and growth - Classified by position on plant

What is the structure and function of epidermal tissues?

- Epidermis: single layer of compact cells over all plant organs o On aboveground organs covered by cuticle Types: o Pavement cells: most numerous and irregular shaped and interlocked to be water tight, lack chloroplasts, transpartents so light can penetrate to PSN tissue o Stomata/guard cells: opening in epidermis for gas exchange Found on leaves and some stems Roots lack stomata Opening controlled by guard cells o Trichomes: minutes hairs on epidermis o Root hairs: tubular outgrowth of root epidermis Greatly increase root surface area Absorb most of water and nutrient for plants

What is the function of epidermal trichomes?

- Minute hairs on epidermis - Function: defense against herbivores - Prevent frost formation - Reflect light in bright locals

What is the difference between sieve cells and sieve tubes?

- Sieve tubes: advanced form o Sieve tube members connect to form tubes o All actively regulated by companion cells o Similar to perforation plats o Sieve pores enable flow between tubes o Only in angiosperms - Sieve cells: primitive type of sieve element o Cell elongated with inclined end walls o Have sieve pore, no sieve plate o Lack companion cells

What is the difference between simple and complex tissue?

- Simple: have one cell type - Complex: multiple cell types

What is the difference between tracheids and vessels?

- Tracheids: narrow tubes tapered at ends o Dead and hollow at maturity o Thick secondary walls with spiraling bands of lignin o Pits in walls allow water movement between cells o Functions: conducts water/minerals, mechanical support o Found in all vascular plants - Vessels: tubes of connected vessel elements o Thick secondary walls with bands of lignin o Elements open at both ends with perforation plates o Walls with pits for lateral water flow o Functions: conducts water/minerals o Only in angiosperms

What is the difference between open and closed vascular bundles?

- Vascular bundles: arrangment of xylem/ phloem strands o Open: vascular bundle has cambium layer diving xylem and phloem Found in woody dicots o Closed: Vascular bundle lack cambium No secondary growth In monocots and herbaceuous dicots

What makes up the vascular tissue?

- Xylem: 1. Primary xylem: arises from procambium o 2. Secondary xylem: arises from vascular cambium - Phloem: phlos: "bark" o o 2 main types: 1. Primary phloem: arised from procambium o 2. Secondary phloem: from vascular cambium o Function: conducts food from leaves

What is the difference between radial and conjoint vascular bundles?

-radial: xylem and phloem separate along different radii Common in monocot and dicot roots - Conjoint: xylem and phloem are together in same radius Typical of monocots and dicots stems and leaves Collateral: conjoint VB with xylem and phloem side by side

What are glandular trichomes?

: epidermal hairs with secretory function Compromised of stalk and secretory head Ex: oil glands secret essential oils, salt glands export excess salt, digestive glands secrete enzymes

What is a lateral meristem?

arranged parallel to side of an organ - Creates secondary growth - increase in girth - Produce secondary tissues: o Vascular cambium: thin cylinder of cells around roots and stems Produce secondary vascular tissue Cork cambium: second cylinder outside vascular cambium Produces cork and bark

What are the roles to companion cells?

associated with sieve tubes - 1 to many per tube member - Have thin primary walls and large nuclei - Packed with mitochondria and ribosomes - Linked to members by plasmodesmata - Regulate activity of tube members

What is sclerenchyma?

cell dead at maturity - Thick lignified secondary walls - Function in mechanical support and protection o Sclereids: short cells with very thinck, hard walls Form durable tissue layers Form cores of apples and grit of pears "stone cells" o Fibers: strands or bundles of slender cells Surround cavity called tumen Commercial use: flax, hemp, jute

What is parenchyma?

have thin, primary without lignin - Living cells with prominent nuclei - Usually 14-sided cells at maturity - Form filler in soft parts of plants - Comprise pith and cortex of roots and stems - Often have airspaces between cells o Aerenchyma: extensive airpsaces in aquatic plants for buoyancy o Chorenchyma: contain chloroplasts and preform PSN in leaves and stems

What are lacticifers?

latex producing glands May be single cell or tubes of several cells Latex used by plants for defense

What is a hydathode?

leaf pores that exude drops of water o Faciliate guttation

What is a apical meristem?

located at the tips of roots and stems, apexes of leaves - Create primary growth - length growth - Creates new ___ and leaves - Gives rise to 3 primary meristems: o Protoderm: produce dermal tissue o Ground meristm: produce ground tissue o Procambium: produce primary vascualar tissues

What is the structure and function of the periderm?

secondary dermal covering - Found in roots and stems of woody dicots - Replace epidermis as stem gorws in girth - Outer cells: cork infused with suberin (cuticle, lignin) - More resistant to injury and water loss - Lenticels allow for gaseous exchange

What are nectaries?

secrete sugary water o Attracts pollinating insects o Can be floral or extra-floral

What is a cuticle?

thin film of cutin and waxes - Barrier to water loss and injury