Kingdom Plantae

Introduction to Plants What is a plant? What is a plant? Plants: are multicellular eukaryotes have cell walls made of cellulose develop from multicellular embryos carry out photosynthesis using green pigments chlorophyll a and b

Introduction to Plants Most plants are autotrophs, although a few are parasites or saprobes that live on decaying matter Most plants are autotrophs, although a few are parasites or saprobes that live on decaying matter Some plants can reproduce asexually Some plants can reproduce asexually Plants have a life cycle with alternation of generations Plants have a life cycle with alternation of generations They have a haploid gametophyte stage, where the haploid cells (egg and sperm) fuse together to produce a diploid cell. They also have a diploid sporophyte stage, where spores produce a new individual by mitosis.

Gametophyte Sporophyte All plants have alternation of generations. There is an evolutionary trend from a dominant autotrophic (self- feeding) gametophyte and a nutritionally dependent sporophyte to a dependent gametophyte and a dominant autotrophic sporophyte. This is exemplified by exploring the life cycles of a moss, a fern, and an angiosperm.

What do plants need to survive? Sunlight ~ photosynthesis, photosynthetic organs on leaves to absorb energy from the sun Sunlight ~ photosynthesis, photosynthetic organs on leaves to absorb energy from the sun Water and Minerals ~ plants need to obtain and deliver water and minerals to their cells Water and Minerals ~ plants need to obtain and deliver water and minerals to their cells Gas Exchange ~ plants require oxygen to support respiration and carbon dioxide to carry out photosynthesis Gas Exchange ~ plants require oxygen to support respiration and carbon dioxide to carry out photosynthesis Movement of Water and Nutrients ~ plants have specialized tissues that distribute he products of photosynthesis throughout the plant body Movement of Water and Nutrients ~ plants have specialized tissues that distribute he products of photosynthesis throughout the plant body

Early Plants The first plants evolved from an organism much like the multicellular green algae living today The first plants evolved from an organism much like the multicellular green algae living today Early plants were dependent on water to complete their life cycle Early plants were dependent on water to complete their life cycle Over time, plants evolved and adapted so that they were: Over time, plants evolved and adapted so that they were: -More resistant to the drying rays of the sun -More capable of conserving water -More capable of reproducing on dry land

Evolution of plants

The beginning of the Carboniferous had a more uniform, tropical, and humid climate throughout the year than exists today. Seasons, if any, were indistinct. The number of plants during the Carboniferous became more numerous. Vascular plants began to dominate the landscape and gymnosperm-like plants began to appear. Angiosperms would appear much later.

Early Vascular Plants a. Evolved from Charophytes, a group of green algae b. Cooksonia oldest vascular plant fossil ; Rhynia c. Late Silurian ( million years BP) d. No roots or leaves e. Vascular plants dominated by the Devonian ( million BP)

Plant Adaptations a. Development of a 1) vascular system: xylem and phloem, 2) ground tissues: comprise the main plant body, and 3) dermal tissue: provide protective covering to plants b. Developed a waxy cuticle c. Upright growth habit; lignin (for structure and conduction) and cellulose d. Stomata for gas exchange (O 2, CO 2, H 2 O) e. Sex organs are multicellular gametangia f. Fertilization of egg develops into an embryo g. Roots evolved from underground stems

A question… What was the greatest “challenge” to plants as they began to live on land? What was the greatest “challenge” to plants as they began to live on land? Answer: Acquiring, transporting, and conserving water.

Plant Kingdom Overview The plant kingdom is divided into 4 groups based on 3 important features: The plant kingdom is divided into 4 groups based on 3 important features: 1) water-conducting tissues (vascular) 1) water-conducting tissues (vascular) 2) seeds 2) seeds 3) flowers 3) flowers

Four Major Groups of Plants and Their Respective Phyla Four Major Groups of Plants and Their Respective Phyla Bryophytes - nonvascular; reproduce via spores, seedless plants; includes the mosses, liverworts, and hornworts Phylum Bryophyta (Mosses), Phylum Hepaticophyta (Liverworts), Phylum Anthocerophyta (Hornworts) Seedless Vascular Plants - vascular plants which are seedless, use spores in reproduction; includes the ferns and fern allies Phylum Psilophyta (Whisk ferns), Phylum Lycopodophyta (Club Mosses), Phylum Sphenophyta (Horsetails), Phylum Pterophyta (Ferns) Gymnosperms - vascular, naked seed producing plants; includes conifers, cypress, cedars, cycads, etc. Phylum Cycadophyta (Cycads), Phylum Ginkgophyta (Ginkgo), Phylum Coniferophyta (Conifers), Phylum Gnetophyta (Welwitschia) Angiosperms - vascular plants, producing protected seed; includes all flowering plants Phylum Anthophyta (Flowering plants) Class Dicotyledones, Class Monocotyledones, Class Magnoliids

To test your memory… Question: Question: What are the 3 most important features of plants that botanists use to classify them into 4 groups? Answer: Water-conducting tissue, seeds, and flowers.

To test your memory… Question: Question: From what kind of organism did all plants evolve? Answer: Green algae.

NONVASCULAR AND SEEDLESS VASCULAR PLANTS

Phylum Anthocerophyta (Hornworts) Phylum Hepaticophyta (Liverworts) Phylum Bryophyta (Mosses) Bryophytes- nonvascular; reproduce via spores, seedless plants; includes the mosses, liverworts, and hornworts

Bryophytes Definition: Definition: - nonvascular plants (do not have specialized tissues that conduct water and nutrients) - draw up water by osmosis - have life cycles that depend on water for reproduction

It is now widely accepted (from morphological and molecular work) that a group of green algae called the charophytes represent the sister group to land plants.

Mosses and Liverworts Mosses (Bryophytes) form into a green velvety mass. Mosses (Bryophytes) form into a green velvety mass. Liverworts are flat foliose-like plants and mosses have thin upright shoot containing capsules. Liverworts are flat foliose-like plants and mosses have thin upright shoot containing capsules.

Mosses and Liverworts The plants are attached to the soil with small root-like structures called rhizoids, which absorb water and minerals from the soil. They are not true roots because they do not contain vascular tissue. The plants are attached to the soil with small root-like structures called rhizoids, which absorb water and minerals from the soil. They are not true roots because they do not contain vascular tissue. These plants lack true stems or true leaves. They do have flat leaf-like structure. In moss, the small leaves are arranged spirally on thin stem-like structures and bear a capsule containing spores. These plants lack true stems or true leaves. They do have flat leaf-like structure. In moss, the small leaves are arranged spirally on thin stem-like structures and bear a capsule containing spores. These plants lack conducting tissue, therefore, they cannot grow very tall. These plants lack conducting tissue, therefore, they cannot grow very tall.

Challenge trivia! Liverwort, hornwort, milkwort, spiderwort – these are all names of plants. What does the ending –wort mean and where did it come from? Liverwort, hornwort, milkwort, spiderwort – these are all names of plants. What does the ending –wort mean and where did it come from? The ending –wort means “plant”, and it can be traced to Old English, when 800 years ago plants were referred to as wyrt.

Bryophytes- (9000 Mosses), (6000 Liverworts) and (100 Hornworts) a. Have no conductive tissues, thus no way to efficiently assimilate photosynthates or minerals; since they are reliant on diffusion, they are typically very small b. Three distinctive phyla c. Absorptive structures called rhizoids; “leaflike” blades/leaves d. Typically separate male and female gametophytic plants; sperm must swim through a thin film of water to fertilize the egg; a diploid zygote forms and grows into a mature moss sporophyte; spores will be released from the sporophyte and will germinate to form a protonema which further develops into the gametophyte e. The gametophytic generation is the dominant form of the life cycle f. Liverworts may exhibit a leafy morphology or a thalloid (thallus) body form; some reproduce asexually using gemmae cups containing gemma (small multicellular spheres that contain many haploid cells)

Homosporous- one spore type produced and released) Hetrosporous- two spore types produced one developing into a male gametophyte, the other into a female gametophyte

Life cycle of a moss The gametophyte generation dominates. Differentiation of the growing tip of the gametophyte produces antheridia in males and archegonia in females. The sperm and egg are produced in the antheridia and archegonia, respectively. Sperm are carried to the archegonia in water droplets. The sperm unites with the egg to form a diploid zygote.

Life cycle of a moss The zygote is the sporophyte generation. A sporophyte develops an enlarged capsule. Inside the capsule (sporangium), meiotic division takes place and haploid spores are formed. When the capsule breaks open these spores are released and germinate into new plants when they find a suitable environment. The spore develops a branching filament called a protonema. After extensive growth, the protonema develops buds, which develop into leaf shoots.

More questions to test your memory… Is the gametophyte haploid or diploid? Is the gametophyte haploid or diploid? Haploid. Where does the sporophyte develop? Where does the sporophyte develop? It develops within the gametophyte.

More questions to test your memory… What does the sporophyte produce? What does the sporophyte produce? Spores When a spore germinates, what does it produce? When a spore germinates, what does it produce? Protonema

Seedless Vascular Plants (11,000 Ferns), (Club Mosses 1,000), (Horsetails 15) and (Whisk Ferns 12)

1. Phylum Psilophyta (Whisk ferns) 2. Phylum Lycopodophyta (Club Mosses) 3. Phylum Sphenophyta (Horsetails) 4. Phylum Pterophyta (Ferns) Seedless Vascular Plants Seedless Vascular Plants- plants which have distinct tissues for conducting water and nutrients throughout the plant; use spores for reproduction instead of seeds; there are four phyla of SVP

Evolution of Vascular Tissue Vascular plants had a new type of cell that was specialized to conduct water Vascular plants had a new type of cell that was specialized to conduct water Tracheids: hollow cells with thick cell walls that resist pressure, connected end to end Tracheids: hollow cells with thick cell walls that resist pressure, connected end to end ~are key cells in the xylem: a form of vascular tissue that carries water upward from the roots to the rest of the plant Phloem: a second type of vascular tissue that transports solutions of nutrients and carbohydrates produced by photosynthesis Phloem: a second type of vascular tissue that transports solutions of nutrients and carbohydrates produced by photosynthesis Vascular plants also produce lignin, a substance that makes cell walls rigid and allows plants to grow upright and tall Vascular plants also produce lignin, a substance that makes cell walls rigid and allows plants to grow upright and tall

Seedless Vascular plants Seedless vascular plants include: club mosses, horsetails, and ferns Seedless vascular plants include: club mosses, horsetails, and ferns Like other vascular plants, they have: Like other vascular plants, they have: ~ roots: underground organs that absorb water and nutrients ~ leaves: photosynthetic organs that contain vascular tissue gathered into veins of xylem and phloem ~ stems: supporting structures that connect roots and leaves and carry water and nutrients between them

Another question… Why were tracheids one of the great evolutionary innovations of the plant kingdom? Why were tracheids one of the great evolutionary innovations of the plant kingdom? Tracheids provided for the movement of water and plant fluids over great distances, even against gravity. This allowed plants to grow large and tall.

Club Mosses A. Once dominant plants in the landscape, 300my ago B. Strobilus are present to bear spores C. Some are homosporous, some are heterosporous; If heterosporous, male microspores (n) will be produced along with female megaspores (n); once shed, these spores will develop into male and female gametophytes which will produce sperm and egg respectively; when the egg is fertilized a sporophyte (2n) will form; within the strobilus spores form and the process repeats

Horsetails A. Once dominant plants in the landscape, 300my ago B. True roots, stems and small leaves (reduced megaphylls); hollow jointed stems impregnated with silica; green stem main photosynthesizing part C. Reproductive branches bear a terminal cone-like strobilus D. Life cycle is similar to fern life cycle; also requires water

Ferns a. Conductive tissues present; xylem and phloem!! Thus may be larger, and allowed for true leaf evolution! b. Two Basic Leaf Types: 1) Microphyll- possess a single vascular strand and are typically small and 2) Megaphyll- possess more than one vascular strand and are typically larger than microphylls; webbing effect seen c. Sporophyte is the dominant generation! Consists of roots, rhizomes and fronds; fiddleheads are young fronds; sori appear on the fronds and house spores d. Spores (n) germinate into a prothallus (n) which will produce eggs (n) in the archegonium and sperm (n) in the antheridium; they combine to form a zygote (2n); the zygote grows into a young sporophyte (2n); the mauture sporophyte of most ferns produce only one type of spore (homosporous- one spore type produced and released); some are hetrosporous, that is they produce two spore types, one developing into a male gametophyte, the other into a female gametophyte Water is required for the sperm to use as a medium to swim to the egg

Life cycle of a Fern The diploid sporophyte stage is dominant in the life cycle. Fern sporophytes produce haploid spores in sporangia, which are grouped into clusters called sori. Spores are released from sporangia and when they germinate, they develop into haploid gametophytes.

Life cycle of a Fern The gametophyte develops independently of the sporophyte. The underside of the gametophyte has antheridia and archegonia, and fertilization occurs when the sperm swims to the eggs in a thin film of water. The diploid zygote grows into a new sporophyte plant.

The Sporophyte continues to grow while the Gametophyte dies.

Final questions… Which generation in the life cycle of the fern is the large, leafy plant we all know? Which generation in the life cycle of the fern is the large, leafy plant we all know? The sporophyte. How is the gametophyte produced? How is the gametophyte produced? The sporophyte produces spores. A spore will grow into a gametophyte.