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Home , Botany, Gametophyte, Plant reproduction, Sporophyte, Transpiration

(the Study of ) General Review  All plants are:  Eukaryotic  Autotrophic  Multicellular  Walls with w/ a, b, and  May have waxy to prevent loss.  Stomata allow .  Plants probably evolved from green (charophytes)  similarity  Biochemical similarities  similarities

Plant Alternation of Generations – plants grow a separate, haploid to produce ; the same plant exists in two different forms during its , although sometimes it’s hard to differentiate between the forms

Multicellular – (2N) (2N) Unicellular fertilization (N)

Unicellular Gametes ( & ) Multicellular (N) Evolutionary Trend – early plants displayed the gametophyte (n) as the dominant , modern plants show the sporophyte as dominant (2n) (Ex: is HAPLOID, but are DIPLOID)

zygote

GREEN ALGA ANGIOSPERM Classifying Plants

 Plants can be divided into 2 major categories based on their characteristics:  Nonvascular Plants  Do NOT have specialized tissues to transport water and nutrients  Instead, these plants transport water from cell-to-cell by  Vascular Plants  Have specialized tissues to transport water and nutrients in plants  – carries water upward from – carries nutrients and produced by Nonvascular Plants ()

 Short with no specialized tissues to transport water  Major types:   Liverworts  Nonvascular Plants/ Bryophytes

 Mosses  Have that anchor them to the ground (instead of roots)  Depend on water for fertilization  The sperm must swim to the egg  Therefore, nonvascular plants must live in MOIST environments  Gametophyte is the dominant phase of the life cycle

Moss/ Bryophyte Life Cycle

Zygote grows, mature develops into a sporophyte sporophyte while still attached to gametophyte. zygote Diploid Stage Fertilization Meiosis Haploid Stage

Spores germinate. sperm- producing structure male gametophyte egg- producing structure gametophyte Vascular Plants/Tracheophytes

 Have specialized tissues to transport water and nutrients in plants called Xylem & phloem  Vascular plants (tracheophytes) can be divided into 2 categories:  Seedless vascular plants (spores)  (vascular) plants

Seedless Vascular Plants

– A Close Up  Diploid sporophyte is the dominant stage  Have , which are underground stems  : large “” where spores develop  Develop spores in sporangia on underside of fronds  Reproduce using spores  A sorus (plural: sori) is a cluster of sporangia Fern Life Cycle

Sporophyte still attached to gametophyte

sorus zygote Diploid Stage fertilization meiosis Haploid Stage Spores Spores develop are egg released

sperm mature gametophyte germinates Seed (Vascular) Plants

 Have true roots, leaves, and stems  Have the ability to form , which are used for reproduction  Seed plants are the most dominant group of photosynthetic on land  There are 2 types of seed (vascular) plants:  1. (cones)  2. angiosperms () Seed (Vascular) Plants  Gymnosperms = “cone bearers”  “naked seeds” – not enclosed in  Bear seeds directly on the surfaces of cones  Cones = sporophyte that produce (seeds)  Coniferous trees are the major example  Pines, junipers, spruces, etc.

through one surface view of one cone scale (houses two ) Pine Life Cycle ovule

surface view of one cone scale (houses a -producing sac) mature sporophyte seed section through a coat pollen-producing sac zygote seeding Diploid seed fertilization meiosis Haploid form sperm- producing cell form female gametophyte Seed (Vascular) Plants

 Angiosperms = flowering plants  Seeds are enclosed by an  Flowers are reproductive organs  Evolutionary advantage  attract  Flowering plants contain ovaries  Ovaries surround and protect seeds  Ovary develops into a after pollination & helps with when eaten  Examples:  Maple trees, , grass sporophyte

Flowering Diploid Plant Life Meiosis Meiosis Haploid mitosis Cycle without microspores pollination cytoplasmic

two sperm enter ovule female gametophyte Evolutionary for Plants

Nested monophyletic groups

flowering green zygophytes, charophytes bryophytes horsetails ferns gnetophytes plants algae related groups

seed plants (land plants) vascular plants (closely related groups) Transport in Vascular Plants Transport Within Plants

 Water and minerals absorbed by roots are drawn upward in the xylem to the produced by photosynthesis is exported from leaves to other organs via the phloem  Transport can be passive or active Short- and Long-Distance Transport in Plants

 Water and move differently in plants, depending on whether they’re going a short or a long distance  Ie. – walking down the street or taking an airplane across the world Short-Distance Transport 1. Simple /osmosis  substances in one cell move out of one cell, across the cell wall, and into another cell 2. Plasmodesmata  Plasmodesmata are connections between the cytoplasm of adjacent plant cells  Substances move between cells through these openings

Long-Distance Transport

 Over long distances, these 3 processes (simple diffusion, apoplast,& ) take too long  Water and solutes move through xylem and phloem by bulk flow, the movement of a fluid driven by pressure

 Transpiration is the of water from leaves and other parts of the plant; it causes a pull that brings more water up through the xylem  An average maple tree loses more than 200L of water per hour during the summer!  Unless this water is replaced by water absorbed by the roots, leaves will wilt and die (Cohesion-Tension Theory)

 Transpiration works through a combination of evaporation, , adhesion, and cohesion to pull water up the xylem

The Photosynthesis- Transpiration Compromise

 Exposing leaves to the sun and opening stomata (cellular “holes” in the underside of the ) to allow for gas exchange helps photosynthesis, but causes transpiration to occur at a faster rate. Plants balance the loss by controlling when stomata are open. Mechanism for Stomatal Opening & Closing

 Guard cells open and close stomata by changing shape using ion and hormone signals based on plant stress. Plant Structure, Growth, & Development The Diversity of Angiosperms

 Angiosperms (flowering plants) can be divided into 2 major categories:  Monocots –  have one seed leaf (cotyledon)  Dicots –  have 2 seed leaves (cotyledons)

Monocots

 Monocots have only 1 cotyledon (seed leaf)  Examples of monocots:  Corn, , lilies, orchids, palms

Dicots

 Dicots have 2 cotyledons (seed leaves)  Examples of dicots:  , clover, tomatoes, , daisies Woody vs. Herbaceous Plants

 Angiosperms can also be subdivided into woody (produce ) and herbaceous (do not produce wood) plants  Woody plants are made of cells with thick cell walls that support the cell body  Examples: trees, ,  Herbaceous plants do not produce wood as they grow, and instead have smooth stems  Examples: dandelions, sunflowers Plant Life Spans  The lifespan of plants, however, is genetically determined  Annuals – complete their life cycle in 1 year  Examples: marigolds, (lots of plants)  Biennials - complete their life cycle in 2 years  Year 1: germinate & grow roots  Year 2: grow stems & leaves, produce flowers & seeds  Examples: evening primrose, celery  Perennials – live for more than 2 years  Examples: Maple trees, grasses, palm trees Plant Structure

 Plants are made up of a system and a system

The Root System

 What do roots do?  Anchor the plant in the soil  Absorb minerals and water  Store food  Types of root systems  Fibrous root system  Found mostly in monocots  Taproot system  Found mostly in dicots How do roots grow?

 Roots grow down from the tip in a region called the apical , where the cells are dividing quickly

The Shoot System

 The shoot system consists of:  vegetative shoots (which bear leaves)  floral shoots (which bear flowers)  Stems have 3 important functions:  Producing leaves, flowers (reproduction),  Holding leaves up to the sunlight for photosynthesis  Transporting substances between roots and leaves How do stems grow?

 Primary growth  Increase in length  Occurs by cell divisions in apical meristem (at top of shoot)   Increase in width  Occurs by cell divisions in the lateral (outward growth)

The Shoot System: Leaves

 Leaves are the primary photosynthetic organs of most vascular plants  Most leaves have a flattened blade and a , which is the stalk that attaches the leaf to the stem

Tissues in Plants

 All 3 plant organs (root/stem/leaf) have dermal, vascular, and ground systems  Dermal Tissue System  Outer protective covering, similar to our skin   Protects the plant from water loss and disease  The cuticle is a waxy coating that helps to prevent water loss Tissue Systems in Plants

System  Carries out long-distance transport of materials within the plant  Xylem and phloem are examples of vascular tissues  System  Pith (inside vascular tissue) and (outside vascular tissue) are examples of ground tissue  Inner cells specialized for storage, photosynthesis, and support

Flower Structure

 Flowers are the reproductive structure of angiosperms  :  Enclose the before it opens  Protect while it’s developing  :  Usually brightly colored to attract pollinators Flower Structure

:  The male portion of a flower  Made up of an anther and a filament  The anther produces haploid pollen grains by meiosis  Most flowers have multiple stamens Flower Structure

 Carpels/Pistils:  The female portion of a flower  :  Sticky – to trap pollen  Style:  Hollow tube which connects stigma and ovary  Ovary:  Produces female gametes (ovules)  Fruit grows from an expanded ovary

Seed Dormancy

 Seed dormancy means that a seed will not germinate, even if sown in a favorable place, until a specific environmental cue causes them to break dormancy  Seed dormancy increases the chances that will occur at a time and place most advantageous to the  How did we break dormancy in our lab?? Stages of Seed Germination

(1) The seed absorbs water, causing it to expand and rupture its seed coat (2) The embryo resumes growth, digesting the storage materials of the (3) The (embryonic root) emerges from the germinating seed (4) The shoot tip breaks through the soil surface

Stages of Seed Germination Plant

 When plant clone themselves by asexual reproduction, it’s known as

Asexual Reproduction

 Fragmentation is the separation of a parent plant into parts that re- form whole plants  This of asexual reproduction is used to produce clones from cuttings (common with houseplants)

Plant Responses to Internal & External Signals Plant Hormones

 REVIEW: Hormones are chemical signals that coordinate the various parts of an organism  A hormone is a compound produced in one part of the body which is then transported to other parts of the body, where it triggers responses in target cells and tissues  Examples of human hormones:  Adrenaline, testosterone, estrogen, epinephrine… Plant Hormones

 There are 5 major classes of plant hormones:  -  Auxin

 Stimulates stem elongation  Stimulates fruit development  Involved in (bending to light) and (growing UP)

Cytokinins

 Stimulate and growth  Stimulate  Stimulate germination and flowering

Gibberellins

 Trigger seed and bud germination  Promote stem elongation and leaf growth  Important in fruit growth Ethylene

 Promotes fruit ripening  Senescence (aging) is a progression of irreversible change that eventually leads to death  Caused, at least in part, by ethylene  “One bad spoils the whole bunch” Abscisic Acid

 Induces seed dormancy  Anti-  Inhibits  Anti-  Inhibits fruit ripening  Anti-ethylene  Closes stomata during water stress, allowing many plants to survive droughts

Tropisms

 Tropisms are growth responses that result in curvatures of whole plant organs toward or away from a stimuli  There are three major stimuli that induce tropisms  Light (Phototropism)  Gravity (Gravitropism/Geotropism)  Touch (Thigmotropism)

Phototropism

 Phototropism is the growth of a shoot towards light  This is primarily due to the action of auxin  Auxin elongates the cells on the non-light side

Plant Defenses

 Plants defend themselves against in several ways  Physical defenses, such as thorns  Chemical defenses, such as producing distasteful/toxic compounds