KINGDOM PLANTAE A Characteristics of Plants 1 Plants

KINGDOM PLANTAE A. Characteristics of Plants 1. Plants are multicellular eukaryotes with welldeveloped tissues. 2. Plants live in a wide variety of terrestrial environments, a. Land existence is an advantage to photosynthesis; water filters much light. b. Carbon dioxide and oxygen are in higher concentrations and diffuse more rapidly in air. 3. Land plants must have adaptations to reduce the loss of water, a. Leaves and stems are covered by a waxy cuticle that holds in water. b. The leaves have openings (stomates) that open and close to regulate gas and water exchange. 4. A 11 plants protect the embryo from desiccation and some protect their entire gametophyte generations. 5. In some plants, pollen grains are transported by wind or animals to the egg, and the embryo.

B. Plant life cycles 1. Plants have a two-generation life cycle called alternation of generations. a. Sporophyte generation is a diploid generation producing haploid spores by meiotic cell division. b. Gametophyte generation is a haploid generation producing haploid gametes by mitotic division. C. Nonvascular plants 2. Plants are divided into two main groups: nonvascular and vascular plants. 3. Nonvascular plants include: (division Bryophyta) a. hornworts b. liverworts c. mosses 4. Nonvascular plants lack specialized tissues for transporting water, minerals, and organic nutrients. 5. They lack true roots, stems, and leaves, although they have root-like, stem-like, or leaf-like structures. 6. The gametophyte is the dominant (most conspicuous) generation,

a. Flagellated sperm swim to the vicinity of the egg in a continuous film of water. b. The sporophyte is attached to and derives nourishment from the photosynthetic gametophyte. 7. Nonvascular plants are quite small; the largest being is no more than 20 cm tall, a. Because sexual reproduction involves flagellated sperm, they are usually found in moist habitats. b. Mosses compete well in harsh environments because the gametophyte can reproduce asexually. 8. Mosses can dry up; later, when water is available, they photosynthesize again. D. Mosses 1. About 12, 000 species of mosses are in the division Bryophyta. 2. Mosses are found in the Arctic through the tropics to parts of the Antarctic. 3. Moss prefers damp, shaded localities; some survive in deserts, others in bogs and streams. 4. Mosses store much water; when they dry out, the become dormant; when it rains, become green. .

5. Copper mosses live only in the vicinity of copper and serve as an indicator of ore deposits. 6. Luminous moss lives in caves; cells shaped like lenses focus light on Some "mosses" are not true mosses: a. Irish moss is an edible alga. b. Reindeer moss is a lichen. c. Club mosses are vascular plants, d. Spanish moss, which hangs from trees in the southern U. S. , is a flowering plant. 7. Most mosses can reproduce asexually by fragmentation. 8. Life cycle begins with alga-like protonema developing from germination of a haploid spore, a. Three days of favorable growing conditions produce upright shoots covered with leafy structures. 1. Rhizoids anchor the protonema, to which the shoots are attached. 2. The shoots bear antheridia and archegonia at their tips. 3. Antheridia produce flagellated sperm which need external water to reach eggs in archegonia

4. Fertilization results in a diploid zygote that undergoes mitotic division to develop a sporophyte. b. The sporophyte consists of a foot (which grows down into the gametophyte tissue starting at the former archegonium), a stalk, and an upper capsule (sporangium) where spores are produced. 1. At first the sporophyte is green and photosynthetic. 2. At maturity it is brown and nonphotosynthetic. E. Uses of Nonvascular Plants 1. Sphagnum (bog or peat moss) has tremendous ability to absorb water and is important in gardening. 2. Sphagnun does not decay in some acidic bogs; the dried peat can be used as fuel. F. Adaptation of Nonvascular Plants 1. Nonvascular plants are limited by lack of structural vascular tissue and need for water for sperm. 2. They have advantages living on stone walls, etc. and contribute to soil formation.

Vascular plants (Division Tracheophyta) A. Vascular Tissue 1. Xylem is vascular tissue that conducts water and minerals up from the soil. 2. Phloem is vascular tissue that transports organic nutrients from one part of the plant to another. B. Organs of Vascular Plants 1. Roots absorb water and minerals from the soil. 2. Stems conduct water and minerals to leaves and conduct organic nutrients from leaves to roots. 3. Leaves are adapted to maximize photosynthetic activity; they are covered by a waxy cuticle. 4. Leaves have openings (stomates) that open and close to regulate gas and water exchange. C. Life Cycle of Vascular Plants 1. The diploid sporophyte generation is dominant; this is the generation that has vascular tissue. . 2. If a faulty gene is present, being diploid can mask it with a functional gene.

D. Reproduction in Vascular Plants 1. Seedless vascular plants (ferns and their allies) disperse their species by producing windblown spores. a. When spores germinate, a large gametophyte develops independent of sporophyte for nutrition. b. Antheridia of gametophyte release flagellated sperm that swim in a film of water to archegonia of the gametophyte, where fertilization occurs. 2. 1 n seed plants there is a separate microgametophyte (male) and megagametophyte (female). 3. They are dependent on the sporophyte which is fully adapted to land. a. Microspores develop within a microsporangium as a result of meiotic cell division. 1. Haploid microspore develops into grains, immature microgametophytes retained in microsporangium. 2. When released, the pollen grains develop I nto sperm-bearing microgametophytes.

3. In evolution of vascular plants, microgametophytes (pollen grains) replaced external swimming sperm. b. Megaspores develop within a megasporangium as a result of meiotic cell division. 1. Haploid megaspores develop into eggbearing megagametophytes, while still retained in an ovule. 2. The megagametophyte is dependent on the sporophyte, since it and the subsequent embryo are retained within the ovule that develops into the seed. E. Seedless Vascular Plants l. The seedless vascular plants include: a. whisk ferns b. club mosses c. horsetails, d. and ferns. F. Ferns 1. 12, 000 species of ferns. 2. Ferns are widespread, and especially abundant in warm, moist tropical regions. 3. Ferns range in size from low-growing moss-like forms to tall trees.

4. Fronds are variable in size and shape. 5. Nearly all fronds first appear as a fiddlehead which unrolls as it grows. 6. Uses of Ferns are used heavily as ornamental plants by florists. b. Fern wood is very decay resistant. c. Fern medicines are used by natives to stop bleeding after childbirth; also as an expectorant. 7. Adaptation of Ferns a. A water-dependent gametophyte lacks vascular tissue and is separate from the sporophyte. b. Flagellated sperm require an outside source of water in which to swim to the eggs. c. Once established, bracken fern spreads to drier areas by asexual reproduction. 8. Life cycle of a fern can begin with production of spores by meiotic cell division within sporangia, located in sort on underside of leaflets, a. Spores are released and disperse largely by wind. b. A spore germinates into a prothallus which grows to develop antheridia and archegonia underneath,

c. Fertilization occurs if water is present; flagellated sperm swim from antheridia to archegonium. d. Resulting zygote begins its development inside archegonium but embryo soon outgrows the space, e. Sporophyte becomes visible as the first leaf grows above and as roots develop below the prothallus. f. Young sporophyte develops a root-bearing rhizome from which fronds project. A. The Life Cycle of Seed Plants 1. Gymnosperms include the: a. conifers b. cycads c. ginkgo 2. There are separate microgametophytes (male) and megagametophytes (female). 3. Microspores develop immature microgametophytes, pollen grains, still retained in a microsporangium. 4. After they are released, pollen grains develop into mature, sperm-bearing microgametophytes.

5. Pollination is the transfer of pollen to the vicinity of the megagametophyte. 6. Sperm is delivered to an egg through a pollen tube; no external water is required for fertilization. 7. The megaspore develops into an egg-bearing megagametophyte while still retained within an ovule. 8. An ovule is the sporophyte structure that holds the megasporangium and then the megagametophyte. 9. After fertilization, the ovule becomes an embryonic plant enclosed within the ovule, which becomes the seed. Both the megagametophytes andmicrogametophytes are dependent upon the diploid sporophyte. The sporophyte can evolve into diverse forms without any corresponding changes in the gametophyte. Among seed plants, seeds disperse the sporophytes. a. Seeds are mature ovules containing embryonic sporophyte and stored food enclosed in protective seed coat.

b. Seeds are resistant to adverse conditions: dryness and temperature extremes. c. A food reserve supports the emerging seedling until it can exist on its own. d. Survival value of seeds contributes greatly to success of seed plants, and their present dominance. e. Survival value of seeds contributes greatly to success of seed and seed coat. release winged seeds in the fall of the second season. G. Uses of Gymnosperms 1. Gymnosperms supply wood used for building construction and paper production. 2. They produce many valuable chemicals extracted from resin. H. Adaptation of Gymnosperms 1. Gymnosperms withstand heat, dryness, and cold, as a result of having well-developed roots and stems, tough, small needles with a thick cuticle. 2. Pollen production has eliminated reliance on external water.

3. Enclosure of the dependent megagametophyte in an ovule protects it during its' development. 4. . Embryo is protected within seed and is provided nutrients that support growth following germination. Angiosperms Are Flowering Plants l. Over 235, 000 species of angiosperms (flowering plants) 2. Angiosperms produce seeds enclosed in fruit. 3. This group contains six times the number of species of all other plants combined. 4. Angiosperms live in all habitats from freshwater to desert and from tropics to subpolar regions.

5. Flowering plant size ranges from microscopic duckweed to Eucalyptus exceeding 100 m tall. 6. They are important in everyday human life: clothing, food, medicine, and commercial products. 1. Today angiosperms are either woody or herbaceous. 2. Angiosperms adapted to a wide range of climatic zones are perennials or annuals. a. Perennials live two or more growing seasons; they die back seasonally in herbaceous plants. b. Annuals are plants that live for only one growing season.

C. Classification of Flowering Plants 1. Angiosperms are divided into two groups: dicotyledons and monocotyledons. 2. Dicotyledons have these features: a. either woody or herbaceous, b. flower parts usually in fours and fives, 3. Sepals are outer ring of modified leaves of flowers; usually green, they enclose flower before it opens. 4. Pet a Is are a ring of modified leaves inside of sepals; large and colorful, they help attract pollinators. 5. Stamens form a whorl inside the petals and around a pistil; slender filament has an anther at its tip. 6. Anther is a modified sporophyll. a. Anther contains microsporangia wheremicrospores (pollen) are produced. b. Anthers likely evolved as a reduction of a sporangium's leaf-like portion.

7. The pistil contains one or more fused carpels; it consists of a stigma, style, and ovary. a. Carpels are modified sporophylls that contain ovules in which megasporangia are located. b. A stigma is a landing platform for pollen and the site where the pollen tube enters the style. c. The style is a slender column that extend from upper part of a carpel and terminates in a stigma. d. Ovary contains one to many ovules which develop(s) into seeds; the ovary develops into a fruit. e. Fruit is a mature ovary and provides a fleshy or dry covering for seeds; may aid in seed dispersal. E. Life Cycle of a Flowering Plant 1. Microsporangia develop within the anther portion of a stamen; the megasporangia develop within ovules. 2. Pollination brings mature microgametophyte (pollen grain) to pistil and pollen tube brings sperm to the ovule. 3. Double fertilization: one sperm fertilizes egg; One sperm unites with polar nuclei to form triploid endosperm.

4. Endosperm is contained within a seed as a nutritive tissue that surrounds and serves as food for embryo. 5. The ovule develops into the seed, and the ovary becomes the fruit. 6. Different kinds of fruit employ different kinds of dispersal mechanisms (i. e. , wind, gravity, water, and animals) for dissemination of seed(s), which thereby promotes dispersal of the species to new locations. 7. Under favorable conditions, the seed germinates to produce a young sporophyte plant. F. Flowers and Diversification 1. Flower variety is related to the numerous means by which flowers are pollinated and fruits dispersed. 2. Although some flowers disperse pollen by wind, many attract specific pollinators (e. g. , bees, wasps, flies, butterflies, moths, and even bats) which carry only a particular pollen.

3. Co-evolution of pollinators and flowers increases probability flower is pollinated by its own species, 4. Flowers promote efficient cross pollination; they also aid in dispersal through production of fruits. 5. There are fruits that utilize wind, gravity, water, and animals for dispersal. 6. Since animals live in certain habitats or have particular migration patterns, they can deliver a fruitenclosed seed to a suitable location for germination and development of the adult sporophyte.

G. Uses of Angiosperms 1. Angiosperms are a major food source for humans, 2. Humans use plant fibers to produce cloth, firewood, and construction materials. 3. Plant oils, spices, and drugs are derived from different parts of angiosperm plants. H. Adaptations of Angiosperms 1. Angiosperms have true roots, stems, and leaves. 2. The vascular tissue is well developed, and leaves are generally broad. 3. The reproductive organs of angiosperms are in Their flowers which often attract pollinators. 4. Flowers also produce seeds enclosed by fruit, which aids in dispersal.