21 1 Plant Cells and Tissues KEY CONCEPT

21. 1 Plant Cells and Tissues KEY CONCEPT Plants have specialized cells and tissue systems.

21. 1 Plant Cells and Tissues Plant tissues are made of three basic cell types. • Parenchyma cells are the most common plant cell type. – store starch, oils and water – help heal wounds to the plant – have thin flexible walls

21. 1 Plant Cells and Tissues • Collenchyma cells provide support to a growing plant. – they are strong and flexible. – celery strings are strands of collenchyma. – they have unevenly thick cell walls.

21. 1 Plant Cells and Tissues • Sclerenchyma cells are the strongest plant cell type. – second cell wall hardened by lignin – die when they reach maturity – used by humans to make linen and rope

21. 1 Plant Cells and Tissues Plant organs are made of three tissue systems. • Dermal tissue covers the outside of a plant. – protects the plant – secretes cuticle of leaves – forms outer bark of trees

21. 1 Plant Cells and Tissues • Ground tissue is found inside a plant. – provides support – stores materials in roots and stems – most commonly made of parenchyma

21. 1 Plant Cells and Tissues • Vascular tissue transports water, minerals and organic compounds. – two networks of hollow tubes stem – xylem transports water and minerals – phloem transports photosynthetic products leaf root

21. 2 The Vascular System KEY CONCEPT The vascular system allows for the transport of water, minerals, and sugars.

21. 2 The Vascular System Water and dissolved minerals move through xylem. • Xylem contains specialized cells. – vessel elements are short and wide – tracheid cells are long and narrow – xylem cells die at maturity tracheid vessel element

21. 2 The Vascular System • The cohesion-tension theory explains water movement. – Plants passively transport water through the xylem. – Cohesion is the tendency of water molecules to bond with each other. – Adhesion is the tendency of water molecules to bond with other substances.

21. 2 The Vascular System • Water travels from roots to the top of trees. – absorption occurs at roots – cohesion and adhesion in xylem – transpiration at leaves

21. 2 The Vascular System • Transpiration is the loss of water vapor through leaves. – water vapor exits leaf stomata – helps pull water to the top branches

21. 2 The Vascular System Phloem carries sugars from photosynthesis throughout the plant. • Phloem contains specialized cells. – sieve tube elements have holes at ends – companion cells help sieve tube elements – unlike xylem, phloem tissue is alive

21. 2 The Vascular System • The Pressure-flow model explains sugar movement. – plants actively transport sugar from the source – sugar flows to the sink due to pressure differences phloem xylem sugars 1 Sugars move from their source, such as photosynthesizing leaves, into the phloem. 3 The sugars move into the sink, such as root or fruit, where the are stored. water 2 Water moves from the xylem into the phloem by osmosis, due to the higher concentration of the sugars in the phloem. The water flow helps move sugars through the phloem.

21. 3 Roots and Stems KEY CONCEPT Roots and stems form the support system of vascular plants.

21. 3 Roots and Stems Roots anchor plants and absorb mineral nutrients from soil. • Roots provide many functions. – support the plant – absorb, transport, and store nutrients – root hairs help absorption

21. 3 Roots and Stems • There are several parts of a root. – root cap covers the tip root cap

21. 3 Roots and Stems • There are several parts of a root. – root cap covers the tip – apical meristem is an area of growth apical meristem

21. 3 Roots and Stems • There are several parts of a root. – root cap covers the tip – apical meristem is an area of growth – vascular cylinder contains xylem and phloem vascular cylinder

21. 3 Roots and Stems • There are two main types of roots. – Fibrous root systems have fine branches. – Taproot systems have one main root. Fibrous root Taproot

21. 3 Roots and Stems Pictures to Study for Test!

21. 3 Roots and Stems Roots – monocots versus dicots. Monocot Dicot

21. 3 Roots and Stems support plants, transport materials, and provide storage. • Stems have many functions. – support leaves and flowers – house most of the vascular system – store water Baobab trees Cactus

21. 3 Roots and Stems support plants, transport materials, and provide storage. • Stems have many functions. – support leaves and flowers – house most of the vascular system – store water – grow underground for storage Ginger rhizomes Potato tubers

21. 3 Roots and Stems support plants, transport materials, and provide storage. • Stems have many functions. – support leaves and flowers – house most of the vascular system – store water – grow underground for storage – form new plants Strawberry stolons

21. 3 Roots and Stems • Some stems are herbaceous and conduct photosynthesis.

21. 3 Roots and Stems • Some stems can be woody, and form protective bark.

21. 3 Roots and Stems • Primary growth increases a plant’s length. • Secondary growth increases a plant’s width.

21. 3 Roots and Stems • Tree rings help determine the age of a tree. bark bands heartwood one year of growth sapwood

21. 3 Roots and Stems Monocot Stem

21. 3 Roots and Stems Dicot Stem

21. 4 Leaves KEY CONCEPT Leaves absorb light and carry out photosynthesis.

21. 4 Leaves Most leaves share some similar structures. • The blade is usually broad and flat. – collects sunlight for photosynthesis – connects to the stem by a petiole blade petiole

21. 4 Leaves • Mesophyll is between the leaf’s dermal tissue layers. cuticle upper epidermis palisade mesophyll spongy mesophyll lower epidermis

21. 4 Leaves • Guard cells surround each stoma. – Stomata open and close when guard cells change shape. – When stomata are open, water evaporates and gas exchanges. – Stomata close at night and when plant loses too much water. guard cells stoma

21. 4 Leaves • Leaves may be simple, compound, or double compound. Simple leaf Compound leaf Double compound leaf

21. 4 Leaves • Leaf veins may be parallel or pinnate. Parallel veins Pinnate veins

21. 4 Leaves • Leaf margins may be toothed, entire, or lobed. Toothed margin Entire margin Lobed margin

21. 4 Leaves Most leaves are specialized systems for photosynthesis. • There are two types of mesophyll cells. – both types contain chloroplasts – palisade mesophyll absorbs sunlight – spongy mesophyll connects to stomata cuticle upper epidermis palisade mesophyll xylem spongy mesophyll phloem lower epidermis stomata

21. 4 Leaves • Leaves have many adaptations. – for extreme temperatures, ex: pine needles

21. 4 Leaves • Leaves have many adaptations. – for extreme temperatures, ex: pine needles – for water loss, ex: cactus spines

21. 4 Leaves • Leaves have many adaptations. – for extreme temperatures, ex: pine needles – for water loss, ex: cactus spines – for aquatic environments, ex: water lily

21. 4 Leaves • Leaves have many adaptations. – for extreme temperatures, ex: pine needles – for water loss, ex: cactus spines – for aquatic environments, ex: water lily – for getting food, ex: Venus’ flytrap

21. 4 Leaves Monocot leaf

21. 4 Leaves Dicot leaf