Kingdom Plantae Characteristics of plants All Plants Eukaryotic

Kingdom Plantae

Characteristics of plants All Plants: Eukaryotic Multicellular Autotrophic Used for Classification: Pigments: chlorophyll, carotenoids, fucoxanthins, xanthophylls Energy Storage: starches Tissues: vascular/non for transporting H 2 O & nutrients Structures: roots, stems, leaves Life Cycles/Alternation of Generations: gametophytes = n, sporophytes = 2 n Reproduction: presence/absence of seed presence/absence of fruit

Characteristics of plants PLANT • Mainly terrestrial and sessile • Display an alternation of generations. – sporophyte and gametophyte are heteromorphic-the two generations look and develop differently from each other. – In algae the gametophyte is dominant, in most plants the sporophyte is dominant. • Sugars made via photosynthesis are used as a fuel source for growth and also stored as the complex carbohydrate starch. • Cell walls are made of cellulose. ROOTS • • anchor The Source of the Oxygen Produced byplant; absorb water and Photosynthesis minerals from the soil (aided Photophosphorylation • Tracing the Pathway of CO 2 by mycorrhizal fungi) LEAF performs photosynthesis CUTICLE reduces water loss; STOMATA allow gas exchange STEM supports plant (and may perform photosynthesis) Surrounding water supports the alga WHOLE ALGA performs photosynthesis; absorbs water, CO 2, and minerals from the water HOLDFAST anchors the alga ALGA

Alternation of Generations

• Unlike algae, plants have vascular tissue – It transports water and nutrients throughout the plant body – It provides internal support – How is vascular tissue arranged differently in C 3 and C 4 plants?

Making the move to dry land Required several evolutionary breakthroughs. What would be the key adaptations needed if you are going from an aquatic to a terrestrial existence? Cooksonia Charophyte Modern angiosperm

Terrestrial Challenges & Adaptations • Air offers no support to fight gravity. • Water is less available which results in dessication, immotility of sperm, lack of absorption, problems with gas exchange and a need for conduction • Nutrients and water are in soil, but CO 2 and light are above ground. • Protective covering to prevent dehydration • Transport system for water & nutrients • Structural system for support (woody tissue) • Discrete organs- roots, stems, leaves & gametangia. • Protective covering for gametes & embryos • Mechanism to allow sperm to get to egg

Cladogram of the major plant groups 4 Major Plant Groups: 1. Bryophytes Nonv ascular Plants 2. Pteridophytes Vascular Plants without Seeds 3. Gymnosperms Vascular Plants with Naked Seeds 4. Angiosperms Vascular Plants with Seeds, Flowers, and Fruits

Avascular Plants : Mosses, Hornworts & Liverworts

Life Cycle of a Moss

Seedless Vascular Plants : Ferns, Club mosses, Horsetails and Whisk ferns New evolutionary adaptations: • Waxy cuticle • Gametangia Features still absent in this group: • No well developed vascular system • No support system • Require water for sperm to swim to egg

Cuticle: waxy covering on the surface of plant stems and leaves which prevents desiccation; Stoma (stomata): microscopic pore surrounded by guard cells in the epidermis of stems and leaves that allows gas exchange

Figure 29. 11 The life cycle of a fern Fern Life Cycle 1, 2

Seedless plants formed vast “coal forests” • Ferns and other seedless plants once dominated ancient forests – Their remains formed coal • Gymnosperms that produce cones, the conifers, largely replaced the ancient forests of seedless plants – These plants remain the dominant gymnosperms today

A pine tree is a sporophyte with tiny gametophytes in its cones • Sporangia in male cones make spores that develop into male gametophytes – These are the pollen grains • Sporangia in female cones produce female gametophytes When do most plants reproduce? Why? • Reproduction and rearing of offspring require free energy beyond that used for maintenance and growth. Different organisms use various reproductive strategies in response to energy availability.

4 Female gametophyte (n) Haploid spore cells in ovule develop into female gametophyte, which makes egg. 5 Male gametophyte (pollen) Egg (n) grows tube to egg and makes and releases sperm. Sperm (n) HAPLOID DIPLOID MEIOSIS Ovule Male gametophyte (pollen grain) Fertilization Scale Sporangium (2 n) Seed coat 3 Pollination HAPLOID Pollen grains (male gametophytes) (n) Embryo (2 n) Integument 1 Female cone bears ovules. 6 Zygote develops MEIOSIS into embryo, and ovule becomes seed. 2 Male cone produces spores by meiosis; spores develop into pollen grains Zygote (2 n) 7 Sporophyte Seed falls to ground and germinates, and embryo grows into tree. Life Cycle of a Conifer

The flower is the centerpiece of angiosperm reproduction • Most plants are angiosperms – The hallmarks of these plants are flowers – The angiosperm plant is a sporophyte with gametophytes in its flowers • The angiosperm life cycle is similar to that of conifers – But it is much more rapid – In addition, angiosperm seeds are protected and dispersed in fruits, Pollen grains which develop from ovaries Anther Stigma CARPEL Ovary STAMEN PETAL Ovule SEPAL

2 Haploid spore in each Stigma Egg (n) ovule develops into female gametophyte, which produces egg. 3 Pollination Pollen grain and growth of pollen tube Ovule Pollen tube 1 Haploid spores in anthers develop into pollen grains: male gametophytes. Sperm Pollen (n) Meiosis HAPLOID Fertilization DIPLOID 4 7 Seed Ovary Seeds germinates, and embryo grows into plant. Ovule Sporophyte Zygote (2 n) Seed coat Food supply 5 Seed Embryo (2 n) 6 Fruit Double Fertilization

Polyploidy in plants • common in plants, especially in 30%-70% angiosperms, are thought to be polyploid. • i. e. Species of coffee plant with 22, 44, 66, and 88 chromosomes suggesting ancestral condition (n) = 11 and a (2 n) = 22, from which evolved the different polyploid descendants. • Polyploid plants are larger, leading to created varieties of watermelons, marigolds, and snapdragons • Plant Probable ancestral haploid number Chromo # Ploidy level domestic oat 7 42 6 n peanut 10 40 4 n sugar cane 10 80 8 n banana 11 22, 33 2 n, 3 n white potato 12 48 4 n tobacco 12 48 4 n cotton 13 52 4 n apple 17 34, 51 2 n, 3 n

Origin of Polyploidy • Accident Doubling Plants, (vs animals), form germ cells from somatic tissues. If the chromosome content of a precursor somatic cell has accidentally doubled (e. g. , as a result of passing through S phase of the cell cycle without following up with mitosis and cytokinesis), then gametes containing 2 n chromosomes are formed. • Naturally occuring As the endosperm (3 n) develops in corn (maize) kernels (Zea mays), its cells undergo successive rounds (as many as 5) of endoreplication producing nuclei that range as high as 96 n. • When rhizobia infect the roots of their legume host, they induce the infected cells to undergo endoreplication producing cells that can become 128 n (from 6 rounds of endoreplication).

Polyploidy and Speciation • When a newly-arisen tetraploid (4 n) plant tries to breed with its ancestral species (a backcross), triploid offspring are formed. These are sterile because they cannot form gametes with a balanced assortment of chromosomes. • However, the tetraploid plants can breed with each other. So in one generation, a new species has been formed.

The structure of a fruit reflects its function in seed dispersal • Fruits are adaptations that disperse seeds

Types of Fruits • Simple Fruits: These fruit types are produced by flowers containing one pistil, the main female reproductive organ of a flower. • Aggregate Fruits: These fruits types are developed from flowers which have more than one pistils. They consist of mass of small drupes that develops from a separate ovary of a single flower. • Multiple Fruits: These fruit types are developed not from one single flower but by a cluster of flowers. • Accessory Fruits: These fruit types are developed from plant parts other than the ovary.

Types of fleshy fruits True berry: have a soft epicarp and the mesocarp and endocarp is fleshly Pepo: berry has an outer wall /rind that is formed from receptacle tissue that is fused to exocarp. Hesperidium: have thick, leathery exocarp and mesocarp. They have a juicy, pulpy endocarp Aggregate fruit: formed from the development of a number of simple carpels from a single flower. Multiple fruit: individual ovaries from different flowers get clustered together forming a fruit. Tomato, Eggplant, Chili pep, Grape, Cranberry, Pumpkin, Gourd, Cucumber, Melon Orange, Lemon, Lime, Grapefruit Blackberry, Raspberry, Boysenberry Pineapple, Fig, Mulberry, Hedge apple Accessory fruit Strawberry There are fruits that are dry fruits and can be differentiated as dry dehiscent and dry indehiscent. Fruit types that contain seeds in a seedpod that opens up and releases the seeds are known as dehiscent fruits. Legume: Sweet pea, Beans, Peanut The indehiscent are those fruit types that do not have a seed pot that opens. Caryopsis: Wheat, Rice , Corn, Rye Nuts: The list of fruits under this type are: Walnut, Acorn

Agriculture is based almost entirely on angiosperms • Gymnosperms supply most of our lumber and paper • Angiosperms provide most of our food – Fruits, vegetables, and grains • Angiosperms also provide other important products – Medications, fiber, perfumes

Interactions with animals have profoundly influenced angiosperm evolution • Angiosperms are a major source of food for animals – Animals also aid plants in pollination and seed dispersal Figure 17. 13 A-C

Connection: Plant diversity is a nonrenewable resource • 20% of the tropical forests worldwide were destroyed in the last third of the 20 th century • The forests of North America have shrunk by almost 40% in the last 200 years

• Some plants in these forests can be used in medicinal ways – More than 25% of prescription drugs are extracted from plants

Resources • • Anatomy & Morphology of Plant Organs The Conquest of Land Plant Evolution Tour Identification of Major Fruits