Lecture # 16 Date _____ Chapter #35~ Plant Structure and Growth

Angiospermophytes: Flowering Plants!

Angiosperm structure Three basic organs: 1) Roots (root system) fibrous: mat of thin roots taproot: one large, vertical root Branching and Root hairs increase surface area for mineral ion and water uptake. 2) Stems axillary bud: between leaf and stem, potential to form branch shoot usu. dormant in young plants. terminal bud: apex (tip) of young shoot, where most shoot growth occurs apical dominance: terminal bud inhibits axillary bud growth (prune?) 3) Leaves Blade (flattened) Petiole (Stalk)

Angiosperms: MONOCOTS VS. DICOTS (Seed leaf) Mono vs. dicot Fibrous root system taproot usu. present

Tissue Distribution in Dicot Stems Vascular bundles (xylem and phloem) Surrounded by ground tissue (xylem faces pith and phloem faces cortex in dicots) Be able to draw and label!

Tissue distribution dicot leaf Be able to draw and label!!

Primary Tissues of Leaves Epidermis/cuticle (protection; prevents desiccation) Stomata Guard cells Mesophyll: ground tissue between upper and lower epidermis palisade (most photosynthesis) spongy (gas circulation)

Structure and Function of leaves Explain the relationship between the distribution of leaf tissues and their functions: Absorption of light Gas exchange Support Water conservation Transport of water and products of photosynthesis

Modified roots, stems and leaves Storage roots– roots swollen with food. (ex. Carrot) STEMS Stem tubers= parts of the stem that grow down into the ground and are used for food storage (ex. Potato) LEAVES Bulbs= leaf bases– used for food storage (ex. Onion, tulip) Tendrils= outgrowths from leaves that allow plants to vine. (ex. Vining plants)

Dicots have… Meristems (perpetually embryonic parts that make new cells for plant growth) apical: tips of roots and buds; primary growth (height of plant) lateral: cylinders of dividing cells along length of roots and stems; secondary growth (girth of plant); Produce wood

Control of Plant Growth Plant growth is controlled by hormones: Ex. Auxin and phototropism Other factors also affect growth… ex.

Terrestrial Plant Support Thickened cellulose Cell turgor Lignified xylem (lignin– a hardening agent found in wood)

End of IB STUFF

Secondary Growth Two lateral meristems http://www.pbs.org/wgbh/nova/vikings/treering.html (TREE RINGS) Two lateral meristems 1. vascular cambium ~ produces secondary xylem (wood) and secondary phloem (diameter increase; annual growth rings) 2. cork cambium ~ produces thick covering that replaces the epidermis; produces cork cells; cork plus cork cambium make up the periderm; lenticels (split regions of periderm) allow for gas exchange; bark~ all tissues external to vascular cambium (phloem plus periderm)

Plant tissue Systems Dermal tissue system (epidermis): single layer of cells for protection Cuticle– waxy coating secreted by epidermis of leaves Root hair epidermis used for absorption Vascular tissue system (material transport) xylem: water and dissolved minerals from roots to shoots 2 cell types: tracheids & vessel elements: elongated cells dead at maturity phloem: food from leaves to roots and fruits sieve-tube members: phloem tubes alive at maturity capped by sieve plates (porous); companion cells (nonconducting) connected by plasmodesmata to sieve tube member. P.681 Ground tissue system– makes up most of the young plant (photosynthesis, storage, support): pith and cortex

Plant Tissue Cell Types Parenchyma primary walls thin and flexible; no secondary walls; large central vacuole; most metabolic functions of plant (chloroplasts) Collenchyma unevenly thick primary walls used for plant support (no secondary walls ; no lignin– a hardening agent) Sclerenchyma support element strengthened by secondary cell walls with lignin (may be dead; xylem cells); Two types = fibers (long, occur in bundles) and sclereids (shorter, irregular, nutshells etc.)

Plant Growth Life Cycles annuals: 1 year (wildflowers; food crops) biennials: 2 years (beets; carrots) perennials: many years (trees; shrubs) Meristems (perpetually embryonic) apical: tips of roots and buds; primary growth lateral: cylinders of dividing cells along length of roots and stems; secondary growth (wood)

Primary growth Roots root cap~ protection of meristem zone of cell division~ primary (apical) meristem zone of elongation~ cells elongate; pushes root tip zone of maturation~ differentiation of cells (formation of 3 tissue systems)

Primary Tissues of Roots Stele~ the vascular bundle where both xylem and phloem develop, (also, the entire collection of vascular tissue in roots and stems) Pith~ central core of stele in monocot; parenchyma cells Cortex~ region of the root between the stele and epidermis (innermost layer: endodermis) Lateral roots~ arise from pericycle (outermost layer of stele); just inside endodermis, cells that may become meristematic

Leaf structure

Summary of primary & secondary growth in a woody a stem PRIMARY PRIMARY LATERAL SECONDARY MERISTEMS TISSUES MERISTEM TISSUES Protoderm Epidermis Secondary phloem Primary phloem Vascular Procambium cambium Secondary Primary xylem xylem Ground meristem Ground Pith & tissue: Cortex Cork cambium Cork Apical meristem of stem Periderm

Hydrophyte Characteristics http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/plants/notes/hydro.htm