Plants II Plant organs Plant organs Root system

Plants II Plant organs

Plant organs § Root system – roots § Shoot system – stem and leaves § Vegetative organs – (allow to live and grow): roots, leaves, stem § Reproduction: flowers, seeds and fruits

Roots § Underground, usually equal to shoot system in size § Anchors and gives support § Absorbs water and minerals § Penetrates soil as it grows § Root hairs increase surface area § Produce hormones

stems § Main axis of plant § Support leaves so that leaves are exposed to as much light as possible § Node – where leaf is attached § Internode – space between nodes § Vascular tissue used in transport § Can store nutrients and water and conduct photosynthesis

leaves § Photosynthesis § Size, shape and texture vary and is used in identification § Blade – wide portion of leaf § Petiole – stalk, attaches blade to stem § Axillary bud – where branch or flower may originate

Monocot vs Eudicot fig 25. 3 § Compare seed leaf, root, stem, leaf and flower § Monocot – 1 seed leaf, xylem and phloem in a ring, vascular bundles scattered, leaf veins parallel, flower parts in 3’s and multiples of 3 § Eudicot – 2 seed leaves, phloem between arms of xylem, vascular bundles in ring, leaf veins in net pattern, flower parts in 4’s, 5’s § Eudicots make up larger group and include most familiar flowering plants § Monocots include grasses and most of food sources, like rice, wheat and corn

Plant tissues § Meristematic tissue = embryonic § Apical meristem – located on tip of stem and roots, growth § produces 3 types of meristem § § § Protoderm epidermis Ground meristem ground tissue Procambium vascular tissue § Woody (non herbaceous), non woody (herbaceous – perennial, dies back in winter)

Epidermal tissue § Forms outer protective covering of plant § Walls of epidermal cells exposed to air are covered with a waxy cuticle § Roots – form root hairs § Stems and leaves – trichomes – hairs that protect form too much sun and moisture reserve § Leaves – guard cells, stomata § Periderm – old woody plants, replaces epidermis § Cork cells – protection § Cork cambium – new cork cells made from § Lenticels – areas of overproduction of cork cells, gas exchange

Ground tissue § Bulk of a plant § 3 types: 1. Parenchyma cells – most abundant, found in all organs of plant, least specialized 2. Collenchyma – thick primary walls, flexible support to immature regions, celery strand 3. Sclerenchyma – thick secondary walls that contain lignin (make walls tough), support mature region of plant

Vascular tissue § Xylem – water and minerals, roots to leaves § Phloem – sucrose and organic molecules (hormones) form leaves to roots § Complex tissues – contain 2 or more kinds of cells § Both extend from roots to leaves § Roots- located in vascular cylinder, stem – vascular bundles, leave – leaf veins

Xylem figure 25. 6 § 2 types of conducting cells, hollow and non-living § Tracheids – tapered ends, contain pits where secondary wall does not form § Vessel elements – larger, perforation plates § Parenchyma cells that store substances

Phloem – fig 25. 7 § Sieve tube members – continuous sieve tube – no nucleus § Companion cells – have nucleus § Connected to sieve tube member by plasmodesmata

Root organization § Root cap – apical meristem, replaced often § Zones § Cell division – primary meristem, mitosis § Elongation – cells lengthen and specialize § Maturation – root hairs, fully differentiated

Eudicot root tissue § § § Epidermis – single outer layer, root hairs Cortex – thin walled parenchyma, food storage Endodermis – boundary between cortex and vascular tissue § Casparian strip – prevents water and mineral ions between cell walls § Vascular tissue – xylem and phloem § Pericycle – first layer of cells § Monocots similar, differ in arrangement of xylem and phloem in a ring, ground tissue is pith

Root diversity § Taproot – grows straight down, fleshy, stores food, carrot, beet § Fibrous root system – in monocots – seen in grasses, strong anchorage § Adventitious roots – develop from shoot system instead of root system, seen in corn, can come above soil line § Root nodules – beans, peas…, nitrogen fixation § Mycorrhizae – plant roots and funugs

Stem organization § Terminal bud – shoot tip protected by bud scales § Leaf and bundle scars – location of leaves that have dropped § Axillary buds – give rise to branches or flowers § Bud scale scar – indicates age of stem, one for each year of growth § Primary meristem primary tissues § Protoderm epidermis § Ground meristem pith (ground tissue) § Procambium cortex (vascular tissue)

Herbaceous stems § § § Non woody, die off in winter, perennial Only primary growth Eudicot, vascular bundle in rings, cortex separate from pith § Monocot – vascular bindles scattered, no well defined cortex or pith

Woody Stems § Primary (length) and secondary (girth of trunks) tissues § Secondary tissues form from lateral meristem: vascular cambium and cork cambium § Vascular cambium produces new xylem and phloem each year § 3 distinct areas: bark, wood and pith

Bark and Wood § Contains periderm § when stem becomes woody, replaces epidermis § Cork, cork cambium and phloem § Removing bark and be fatal to tree § Wood is secondary xylem, girth § Vascular cambium is dormant in winter § Annual ring – sapwood, inner rings heartwood

Stem diversity § Stolons – aboveground horizontal stems, reproduce where nodes touch ground, runners, strawberries § Rhizomes – underground, horizontal stems, some contain tubers (food storage) like potatoes § Corm – bulbous underground stems, gladiolus

Leaf organization § Consist of blade and petiole § Veins are netted in eudicots, parallel in monocot

Cross section leaf § Trichomes – protective hairs § Cuticle – prevent desiccation but prevent gas exchange § Stomata on underside § Mesophyll tissue § Palisade § spongy

Leaf diversity § Simple § Compound § § Pinnately compound Palmately compound § Arrangement § § § Alternate Opposite Whorled § Leaves based on adaptation to environment