Roots, Stems, Leaves and Flowers Plant Physiology Roots, Stems, Leaves and Flowers

Plant Physiology Physiology – understanding how parts of an organism work We will learn how roots, stems, leaves and flowers all work together to keep a plant alive

Plant Identification There are two main categories of angiosperms. Monocots – grasses, grain crops, lilies, gladiolas, and palm trees

Monocots Mono = Single Cot = Short for cotyledon Cotyledon = embryonic leaf Embryo = developing plant offspring located in the seed

Monocots Have four distinct features Veins in leaves are parallel to each other Flower parts are arranged in groups of three Xylem and phloem are arranged in bundles Single embryonic leaf

Vascular System Xylem Phloem Cambium Transports water throughout the plant Phloem Transports food (sugars) throughout the plant Cambium Layer of cells that creates new xylem and phloem

Monocot Vein arrangement Convallaria majalis (lily of the valley) The major veins of monocot leaves are generally arranged parallel to each other along the length of the leaf blade.

Plant Identification Dicots - most of the other plants such as the shrubs, trees, and flowers. Veins in leaves are branched Flower parts are arranged in groups of four or five Xylem and phloem are arranged in layers Two embryonic leaves

Dicot Leaf Venation Helianthus (sunflower) The major veins of dicot leaves are generally arranged in a netted (reticulate) pattern that extends across and down the leaf.

Parallel Leaf Venation Monocot and Dicot Leaf Venation Convallaria majalis (lily of the valley) Helianthus (sunflower) Monocot Parallel Leaf Venation Dicot Netted Leaf Venation

Monocot Flower Parts sepal petal stigma stamen Trillium In most monocots, the flower parts are arranged in multiples of three. This trillium flower has three sepals, three petals, six stamens, and three stigmas on the pistil.

Dicot Flower Parts petal stamen pistil Cydonia oblonga (quince) In most dicots, the flower parts are arranged in multiples of four or five. These quince flowers have five petals, twenty stamens, and five pistils. The stamens are too numerous to count in this image.

Monocot and Dicot Flower Parts petal sepal stamen petal stigma stamen pistil Trillium Cydonia oblonga (quince) Monocot Flower Parts in Multiples of Three Dicot Flower Parts in Multiples of Four or Five

Roots

Functions of a root Water Absorption Anchorage Reproduction Most water enters the plant through the roots Anchorage Holds the plant in one place Reproduction Some roots allow for asexual reproduction Food Storage Store sugars for later use

Roots The type of root will normally help you identify the plant. It will place the plant into a monocot or dicot category.

Types of Roots Tap Root Have a main central root and may have some lateral branching E.g. Carrots e.g. = exempli gratia = for the sake of example

Tap Roots Penetrate the soil to various depths - some only a few inches, others like the mesquite to as deep as 114 ft.

Tap Roots Benefits of a tap root Access deep water Hold plant in more securely Store larger quantities of sugars

Types of Roots Fibrous Have many roots of equal size and a lot of lateral branching Fibrous roots are generally much more dense and closer to the surface

Types of Roots This root system can effectively prevent any other plant from becoming established – e.g.: grasses - idea of a healthy lawn is to compete with weeds

Types of Roots Prop Roots - augment regular roots for anchorage aid - ex: corn - roots come out above soil and help hold plant up

Parts of Roots Epidermis – Outer layer of cells, protecting inner cells Root Hairs – Small hairs that grow from the epidermis, helping water absorption and holding root in place

Parts of Roots Cortex – Area of storage in the root Vascular Cylinder – area that contains xylem and phloem tissues

Parts of a root Root Cap – Layer of cells that protect the growing area of a root Apical Meristem – Meristem – point of new cell development Apical – Tip (end of a branch)

Why Different Types of Roots All plants are in competition with each other for water and nutrients By having different types of roots, the plants can reach different depths in the soil and still live side by side with other plants

Stems

Stems For identification: type of stem (woody or herbaceous), monocot or dicot,

Monocot stem Dicot stem phloem xylem Dicot stem cortex

Primary vs Secondary growth Primary Growth Growing from a specific location In woody stems, often at the ends of the branches (apical meristem) In herbaceous stems, can be at end or at the surface of the soil (e.g. grasses) Secondary growth Growing wider around a trunk

Mature Structure of Woody vs Herbaceous Stems Lack secondary growth - plants only live above ground during the growing season Annuals – plants that live only one growing season

Mature Structure of Woody vs Herbaceous Stems Stems remain soft and flexible. Buds lack protective scales (don’t need to survive harsh conditions)

Mature Structure of Woody vs Herbaceous Stems Woody stems Plants living and growing over multiple seasons have secondary growth (xylem, phloem) increasing diameter of the stems

Mature Structure of Woody vs Herbaceous Stems Annuals – Die at the end of the growing season Fast, frequent reproduction, with many seeds Perennials – Live several growing seasons Slower, less frequent reproduction

Growing season - The time of the year in which most of the plant’s growth occurs - usually in the summer - can be other times Wet season Spring Fall

Specialized Stems Rhizomes - underground horizontal stems (ex: perennial grasses, bamboo) - will grow a plant and roots at a node. Node – Any growth point on a stem or root E.g. ‘eyes’ of a potato.

Specialized Stems Stolons - runners - usually above ground, horizontal stems; will grow a plant and roots at a node - ex: strawberries

Specialized Stems Tubers - several nodes at the end of a rhizome (ex: potatoes) - eyes are axillary buds – where the tuber will grow a plant

Specialized Stems Bulbs - large bud with small stem at lower end - storage in the form of numerous, fleshy leaves - ex: onion, lily, tulip Corms - look like bulbs, but are mostly stem tissue with a few, papery leaves on the outside - ex: gladiolus, crocus

Leaves

Leaves Leaves are where plants conduct photosynthesis to produce most of it’s food. Leaves come in many shapes and sizes

Parts of a Dicot Leaf Leaf blade – expanded, usually flat portion of a leaf Petiole – connects the blade of a leaf to a stem or branch – holds leaf up for better air flow and to catch the light

Parts of a Dicot Leaf Veins – threads of vascular tissue (xylem & phloem) Node – place on a stem where leaves or branches normally attach

Parts of a Leaf Midrib– the primary vein that is seen from the petiole to the tip Spine– Large veins that branch from the midrib Margin– the edge of the leaf blade Base – The lower part of the blade, where the petiole attaches

Tip Midrib Spines Blade Margin Veins Base Petiole

Parts of a Monocot Leaf Sheath – part of leaf that holds leaf to stem – encases stem Ligule – membrane-like tissue extending up from the sheath (on inside) – keeps dirt and moisture out – clear membrane on leaf where attaches to stem

Monocot Leaf Blade Sheath Node Collar Auricle Stem Ligule

Picture showing parts of a grass plant.

Two Types of Leaves Simple leaves – composed of a single blade and a petiole

Two Types of Leaves Compound leaves – are composed of a blade that includes several leaflets and a petiole Two types:

Two Types of Leaves Palmately Compound – (chestnut) – the lobes or divisions come together and are attached at one place at the base

Leaf Blade Palmately Compound Leaf Petiole

Two Types of Leaves Pinnately Compound – compound leaf with the leaflets on two sides, usually along a central vein – ex: ferns, ash, hickory

Leaflets Leaf Blade Pinnately Compound Leaf Petiole

Leaf Arrangement Monocots – have only one type of arrangement – leaf comes off of a node – ex: grasses and grain crops

Leaf Arrangement Dicots – flowering plants Alternate – one leaf per node Opposite – two leaves per node Whorled – three or more leaves per node

Leaf Arrangements

Arrangement of Veins Four types of vein arrangements: Parallel veins – veins are small and run more or less parallel – most are long and narrow – ex: Buckhorn Plantain, grasses and Iris – mostly monocots

Arrangement of Veins Netted veins – are large and small – the small ones connecting to each other to form a net – mostly dicots

Arrangement of Veins Pinnately veined – with one larger midvein and smaller veins coming off along its length – mostly dicots

Arrangement of Veins Palmately veined- with two or more large veins arising at or near the base of the leaf blade (palm) – leaves are usually broad or fat – mostly dicots

Parallel Veins Netted Veins Palmately Veined Pinnately Veined

Monocot Leaf -Vein Arrangement Dicot Leaf – Vein Arrangement Smaller lateral vein Midvein

Leaf Structure

Leaf Structure Epidermis – Tough outside layer of cells that protect the inner cells Divided into Upper epidermis and Lower Epidermis

Leaf Structure Upper Epidermis Lower Epidermis

Leaf Structure Stomata – Openings in the leaf that allow the passage of CO2 and water Stomata can open and close based on the needs of the plant They will typically stay closed when the plant needs to retain moisture, and will open up when there is enough water available

Leaf Structure Stomata open and close due to cells on the edge of the stomata called guard cells Guard cells open and close the stomata by allowing water to enter and leave, causing them to swell or shrink

Leaf Structure Upper Epidermis Guard Cells Lower Epidermis Stomata

Leaf Structure Palisade Cells Elongated cells where most photosynthesis takes place Why are they elongated vertically, and not horizontally?

Leaf Structure Upper Epidermis Palisade Cells Guard Cells Lower Epidermis Stomata

Leaf Structure Spongy Mesophyll Water storage area of the leaf Helps to transport wastes out of the leaf through the stomata

Leaf Structure Upper Epidermis Palisade Cells Spongy Mesophyll Guard Cells Lower Epidermis Stomata

Leaf Structure Vascular System Xylem – Transports water from roots to the leaves (water is necessary for photosynthesis) Phloem – Transports sugars from the leaves to the rest of the plant

Leaf Structure Upper Epidermis Palisade Cells Spongy Mesophyll Vascular System Guard Cells Lower Epidermis Stomata

Flowers Petals – are highly colored portions of the flower. May contain perfume (rose) or nectar glands –to attract pollinators. Number of petals on a flower is often used in the identification of plant families and genera.

Flowers Dicots –have sepals and/or petals in multiples of four or five Monocots – have sepals in multiples of threes

Parts of a Flower Sepals Petals Stamens (anther & filaments) Pedicel Pistil (stigma,style & ovaries)

Seeds

Monocot seeds Contain the embryo (infant plant) Cotyledon (part of the embryo) Seed Coat (protects the embryo) Endosperm (provides nutrients to the embryo ) Radicle – The embryonic root tip

Monocot Seed

Dicot Seed