Plants

What is a plant? Eukaryotic Multicellular Autotrophic

Why are plants important? Food Oxygen Materials (building, paper, clothes) Aesthetics Shelter Medicine

Plant Tissues Vascular Tissue: interconnected cells that make tubes for transport Xylem: move water from the roots to the leaves Phloem: move sugar from roots to leaf buds (Spring) or leaves to roots (Fall)

Figure. 35.9 100 m SUGAR-CONDUCTING CELLS OF THE PHLOEM WATER-CONDUCTING CELLS OF THE XYLEM Vessel Tracheids 100 m Tracheids and vessels element Vessel elements with partially perforated end walls Pits SUGAR-CONDUCTING CELLS OF THE PHLOEM Companion cell Sieve-tube member Sieve-tube members: longitudinal view Sieve plate Nucleus Cytoplasm Companion cell 30 m 15 m

Storage Tissue: stores food as starch Storage Tissue: stores food as starch Collenchyma – crunchy cells – carrots and potatoes

Support Tissue: gives strength to tissues. Sclerenchyma – stick like Support Tissue: gives strength to tissues Sclerenchyma – stick like Xylem

Protective Tissue: keep water in and invaders out. Cork on stems Protective Tissue: keep water in and invaders out Cork on stems Epidermis on leaves – makes a waxy layer called the cuticle

Prickle Rose “thorns” are prickles  “A rose between two prickles.”

Photosynthetic Tissue: Parenchyma/Mesophyll: inside of leaves

Cortical parenchyma cells Figure 35.9 Parenchyma cells 60 m PARENCHYMA CELLS 80 m Cortical parenchyma cells COLLENCHYMA CELLS Collenchyma cells SCLERENCHYMA CELLS Cell wall Sclereid cells in pear 25 m Fiber cells 5 m

Plant Organs Roots: - hold plant in the soil - absorb water and nutrients - store food - reproduction

(a) Prop roots (b) Storage roots (c) “Strangling” aerial roots (d) Buttress roots (e) Pneumatophores

Stems: - support leaves and reproductive structures - can be specialized to store food or water or reproduction (potato, strawberry runners, bamboo shoots) - modified for defense = thorn

Thorn

Leaves: - photosynthesis - can store water (succulent) - modified for defense = spine (cactus) - specialize for reproduction = flowers

Spine

External Structure of Leaf

Leaves: External Structure Blade Petiole Stipule Axillary Bud Veins

Internal Structure of Leaf

Leaf Mesophyll

Leaf Stomata

Leaf Modifications (a) Tendrils. The tendrils by which this pea plant clings to a support are modified leaves. After it has “lassoed” a support, a tendril forms a coil that brings the plant closer to the support. Tendrils are typically modified leaves, but some tendrils are modified stems, as in grapevines. (b) Spines. The spines of cacti, such as this prickly pear, are actually leaves, and photosynthesis is carried out mainly by the fleshy green stems. (c) Storage leaves. Most succulents, such as this ice plant, have leaves modified for storing water. (d) Bracts. Red parts of the poinsettia are often mistaken for petals but are actually modified leaves called bracts that surround a group of flowers. Such brightly colored leaves attract pollinators. (e) Reproductive leaves. The leaves of some succulents, such as Kalanchoe daigremontiana, produce adventitious plantlets, which fall off the leaf and take root in the soil.

Important Structures Stoma: opening for gas exchange Guard Cells: regulate size of stoma Mesophyll: photosynthesis Cuticle: protective waxy layer Vascular Bundle: xylem and phloem – vein of leaf

Types of Plants Non-vascular plants: No xylem or phloem – can only move water and sugar by osmosis and diffusion – keeps them small Ex: Bryophytes: Mosses and the their relatives (Liverworts, Hornworts) - reproduce using spores – produced in specialized structures called sporangia - require water for reproduction – sperm must swim to the egg

Vascular Plants: Have xylem and phloem Types of Vascular Plants: Seedless vascular plants: Reproduce using spores EX: Ferns – produce spores which grow in sprorangia on the underside of the leaf, which is called a Frond

- spores land on ground and grow into a separate plant which produces the eggs and the sperm - water hits this and allows the sperm to swim to the egg and the zygote grows into a new fern Other Types: Horsetails, Ground Pine

Seed Plants: Produce specialized structures (Cones or Flowers) that make egg cells in an ovary and sperm cells which are housed inside of pollen grains - pollen is transferred to the cone or flower by a pollinator (insects, birds, bats) to make a new plant and a food source which is protected inside of a seed and the cone or the developing fruit

Types of Seed Plants Gymnosperms: “naked” seeds – seeds only have a seed coat and are not protected by a fruit Ex: Conifers: cone bearing trees - produce two types of cones: Male cones (make pollen) – very small Female cones (make eggs) – egg is housed in the scales of the cone

pollen is blown by the wind from the male cone to the female cone and fertilizes the egg – cone scales close and protect the developing seed – sperm and egg fuse to make the embryo and other unfertilized eggs divide to make a food source in the seed – after several years the scale opens and releases the seeds – some conifers require the heat and smoke from fire to cause the cones to open and release the seeds

Angiosperms: “combined” seeds – seeds that develop from flowers and have a protective coating around the seeds that is the mature ovary of the plant  fruit - Flowering Plants

Typical Flower Structure and Reproductive Cycle

Reproduction: Ovary produces egg cells, anthers produce pollen (houses the sperm and a specialized cell called the tube cell) - pollen is transferred to the stigma and germinates releasing the tube cell and the sperm cell Tube cell makes a path for the sperm cells to the opening of the ovary

One sperm fertilizes one egg to make the new plant embryo and the other sperm fertilizes two other egg cells to make the food source = double fertilization The food source develops into the seed part that we eat and the embryo develops into the young plant At the same time the wall of the ovary begins to grow and expand forming the fruit to attract animals or help spread the seeds

Types of Fruits: - Dry fruits: sunflower seeds, Maple tree helicopters, burrs, dandelion tufts - Fleshy fruits: Apples, bananas, tomatoes, peppers, cucumbers, avocado, peas, green beans

Types Of Angiosperms: Monocots and Eudicots – “cot” refers to the cotyledon or the “seed leaf” in the seed – the first leaf/leaves that emerge from the growing embryo - embryonic leaves

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts Leaf Veins Roots Vascular Bundles in Roots Vascular Bundles in the Stems Secondary Growth

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts In multiples of 3 In multiples of 4 and 5 Leaf Veins Roots Vascular Bundles in Roots Vascular Bundles in the Stems Secondary Growth

Eudicot Flower: multiples of 4 & 5 From:http://www.csdl.tamu.edu/FLORA/tfplab/rep68.jpg From:http://www.thes eedsite.co.uk/brassica ceae.gif

Monocot Flower: Multiples of 3 From: http://www.emc.maricopa.edu/faculty/farabee/biobk/monocot_flower.gif

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts In multiples of 3 In multiples of 4 and 5 Leaf Veins Parallel Net pattern Roots Fibrous Tap root Vascular Bundles in Roots Vascular Bundles in the Stems Secondary Growth

Eudicot & Monocot Leaf Veination Eudicot – net venation Monocot – parallel venation

Eudicot & Monocot Roots - External Eudicot – tap root Monocot – fibrous roots

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts In multiples of 3 In multiples of 4 and 5 Leaf Veins Parallel Net pattern Roots Fibrous Tap root Vascular Bundles in Roots Xylem in a Circle Xylem in an “X” Vascular Bundles in the Stems Secondary Growth

Monocot Root Cross Section From: http://www.inclinehs.org/smb/Sungirls/images/monocot_stem.JPG

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts In multiples of 3 In multiples of 4 and 5 Leaf Veins Parallel Net pattern Roots Fibrous Tap root Vascular Bundles in Roots Xylem in a Circle Xylem in an “X” Vascular Bundles in the Stems Scattered throughout – look like little faces Along the outer edge Secondary Growth

Monocot Stem Vascular Bundles Xylem Phleom

Monocot Stem Vascular Bundle From: http://iweb.tntech.edu/mcaprio/stem_dicot_400X_cs_E.jpg

Eudicot Stem Cross Section From: http://plantphys.info/plant_physiology/images/stemcs.jpg

Eudicot Stem Vascular Bundle Sclerenchyma Phloem Xylem Vascular Cambium

Characteristic Monocots Eudicots Seed Structure One “seed leaf” – made of one piece Two “seed leaves” – made of two pieces Flowers Parts In multiples of 3 In multiples of 4 and 5 Leaf Veins Parallel Net pattern Roots Fibrous Tap root Vascular Bundles in Roots Xylem in a Circle Xylem in an “X” Vascular Bundles in the Stems Scattered throughout – look like little faces Along the outer edge Secondary Growth Absent Present – forms layers of new growth each year – makes rings of xylem tissue  Annual Rings

Life Cycles: Annuals: live for one year and then die Biannual: grow for one year but do not flower – flower the second year and then die Perennials: live for more than two years and up to thousands