BIO102 Lecture Notes: Kingdom Plantae PDF

Students are allowed to reproduce for their own use NOT FOR SALE BIO102: GENERAL BIOLOGY II MODULE 3: KINGDOM PLANTAE The kingdom Plantae comprises all plants ranging from simple mosses, flowering plants to...

Students are allowed to reproduce for their own use NOT FOR SALE BIO102: GENERAL BIOLOGY II MODULE 3: KINGDOM PLANTAE The kingdom Plantae comprises all plants ranging from simple mosses, flowering plants to complex trees. It members are generally multicellular, photosynthetic eukaryotes that play an important role in ecosystems via production of oxygen and as well serve as the base of most food chains. General Characteristics 1. Members possess well defined cells with nucleus and other membrane-bound organelles (eukaryotes). 2. Most are photosynthetic due to the possession of chlorophyll. 3. They have rigid cell wall made up of cellulose which provides them with structural support. 4. They reproduce through various methods that include, sexual (via seeds or spores), asexual (via runners or cloning) and vegetative reproduction. 5. Many possess specialized structures such as roots, stems, leaves and flowers to survive in terrestrial environments. 6. The kingdom is categorized in to four groups/divisions, namely; Bryophytes, Pteridophytes, Gymnosperms and Angiosperms. Bryophyta/Bryophytes (Non-vascular Plants)  Bryophytes are considered to be the descendants of algae for e.g. Pellia, Funaria, Marchantia  The early stages of a moss gametophyte (Prothallus) are algal like in appearance and tend to suggest that algae were ancestors to these plants.  They are the first plants to survive on land and considered to be transitional between terrestrial and aquatic plants (need moist environment).  They are multicellular with the cells organized into tissues and organs.  Stems, leaves, roots (rhizoids) and reproductive organs are differentiated. Page 1 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE  They are very small in size (less than 20cm in length) and therefore non- vascular, growing very close to the ground.  The life cycle is of heteromorphic i.e. an alternation of generation consisting of a nutritionally independent haploid gametophyte and a dependant diploid sporophyte.  The division Bryophyta consists of 3 classes which are Musci, Hepaticeae and the Anthocerotae. Class: Hepaticeae (Liverworts)  Over 6,000 species are described.  They are naturally found dwelling in damp soil but sometime found on mountain.  The gamatophyte is either thalloid or consist of a stem-like axis with two or three rows of a leaf-like organ.  The gametophyte may be monoecious or dioecious.  Sperms and eggs are produced in gametangia.  Reproduces asexually by fragmentation or gemmae formation.  The sporophyte consists of a basal foot, a middle seta and a terminal capsule.  Examples Marchantia and Riccia Class: Musci  There are over 12,000 species known.  They have the same or similar habitat with liverwort, damp soil.  The moss dominant phase (gametophyte) bears many erect or prostate stem like leafy axis.  The gametophyte may be dioecious or monoecious.  The male reproductive organ is called antheridium, it is club shaped and usually elongated, and it is borne in the axis of leaves or at the end of stem – like axis in terminal cup-like structures. Page 2 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE  The female reproductive organ is called archegonium, it is flask – shaped organ bearing a neck (upper region) and a swollen lower region called venter.  They are attached to the substratum by means of rhizoids  The moss sporophyte (Non dominant phase) usually has a pointed foot at the basal region, a middle long seta and a terminal capsule which opens by a cap, producing millions of spores.  Example Funaria Funaria Species Class: Anthocerotae (Horned Liverworts)  The smallest group with around 100 described species.  Both male and female gametes are found embedded on the gametophye, male at the top while the female is within.  Possess rhizoids, but all their body (thallus) have the ability to obtain water.  The sporophyte consists of a bulbous basal foot, a short meristemic region at the middle portion (no seta) and an elongated pale green capsule.  Example Anthoceros Page 3 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE Life cycle of Bryophytes (Alternation of generation) The life cycle of bryophytes follows the alternation of generations pattern, where they alternate between a dominant haploid gametophyte phase to a diploid sporophyte phase. The gametophyte produces male gametes antherizoids and female gametes ova. The antherizoids are flagellated and produced in antheridia. They move chemotropically from the antheridia to the archegonia entering through the neck, fertilizing eggs inside the ventor. This process leads to the formation of a zygote that develops into an embryo (the beginning of the sporophyte). The diploid, short-lived sporophyte develops from the embryo following cell division and differentiation and depends on the gametophyte for nutritional requirements. It produces capsule inside which haploid spores are produced. Each spore on germination develops into a haploid gametophyte. The gametophyte is long-lived, independent, thus, manufactures its food and obtains other requirements from the substratum on which it is growing using rhizoids. Upon maturity, it produces gametes which following fertilization forms the sporophyte. This type of life cycle is described as an alternation of generation. It is haplodiplontic. Life Cycle of Bryophytes Page 4 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE Pteridophyta/Pteridophytes (Vascular Plants)  The division pteridophyta includes a group of primitive vascular plants commonly called pteridophytes.  The adult plant body in these plants is the sporophyte.  It shows differentiation in to stem, root, and leaves.  The stem is mostly herbaceous.  Leaves may be smaller or larger.  Vascular tissues are present in all the vegetative part of the body.  They have lignified cells.  They are seedless vascular plants.  Most of the living representatives are small in stature.  Pteridophytes have been divide into four classes namely Lycopsida, Sphenopsida, Pteropsida and Psilopsida Class: Lycopsida  About 1,000 species described.  Leaves relatively small and spirally arranged around the stem  Include both homosporous and heterosporous forms.  They reproduce both sexually and asexually.  Sporophylls are borne in strobili. The antherozoids are biflagellate or multiciliate.  The sporophyte is differentiated in to stem, root and leaves. Example Lycopodium Class: Sphenopsida  About 15 species known.  Leaves relatively small, arranged in whorls around the stem  Includes only the homosporous forms.  Asexual reproduction through fragmentation. Page 5 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE  Sporangia are produced upon a specialized structure (Sporangiophore) present at the apex of the stem.  Antherozoids are multiciliate.  Example Equisetum Class: Pteropsida  Over 12,000 species are known.  Leaves relatively large and are called fronds, spirally arranged around the stem.  Include mostly homosporous forms.  Reproduce both sexually and asexually  The sporophtye is differentiated in to stem, leaves and root.  The leaf bears many sporangia on either the margin or the abaxial face of the leaf lamina.  The antherozoids are multiciliate. The sex organs are found on the ventral surface of the heart-shaped prothallus.  Example fern Class: Psilopsida  Only 6 species known.  The sporophyte has a rhizome and aerial shoots which are both dichotomous. The rhizome has unicellular rhizoids lacking roots.  The terminal sporangia are borne single at the tips of short or long branches.  They are homosporous, antherozoids are multiciliate.  Reproduce asexually.  The gametophyte grows under the surface of the ground.  It has rhizoids and as well as bears antheridia and archegonia  Example Psilotum Page 6 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE Life Cycle of Pteridophytes Pteridophytes reproduce through production of spores inside special structures called sporangia which occur on the ventral surface of fertile leaves called sporophylls. Sporangia may sometime be found in groups called sori. The plant may be homosporous producing only one type of spore or heterosporous producing two different types of spores (microspores and megaspores). The spores germinate to produce a haploid gametophyte called prothallus. The homosporous pteridophytes produce bisexual gametophyte while heterosporous pteridophytes produce unisexual gametophyte. In pteridophytes, sexual reproduction is of oogamous type, which characterized by alteration of generations, involving an independent diploid sporophyte and an independent haploid gametophyte phasea. The male sex organ is called antheridia while that of the female is the archegonia. The antheridia produce the antherizoids and the archegonia enclose the egg cell where fertilization occur which is highly dependent on liquid media (this is to enable the antheridia-motile sperm swim to the eggs). The diploid zygote is retained in the archegonial venter where it develops into an embryo. Subsequently it becomes a young sporophyte and grows into an independent adult plant. Thus, the life cycle includes an alternation of diploid sporophytic generation with a haploid gametophytic generation. Sporophytic generation is the dominant in the life cycle. Page 7 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE Life Cycle of Homosporous Pteridophytes Life Cycle of Heterosporous Pteridophytes Gymnospermae/Gymnosperms (Seed-producing Plants) Spermatophytes or phenarogams or flowering plants are seed bearing plants and are divided into two major groups: I. Gymnosperms: (Gymnos – naked; sperma – seed) naked seed bearing plants. II. Angiosperms (Angion – case; sperma – seed) covered seed bearing plants. Gymnosperms are closely related to the higher cryptogams (Non-flowering; seedless plants) on one hand, thus, this group forms intermediate link between the cryptogams and angiosperms. Gymnosperms are seed-producing vascular plants that do not form flowers or fruits. Instead, the seeds are produced on surfaces of leaf-like structures (sporophylls) that aggregate to form cones (specialized seed bearing structures within which the seeds develop). Shortly after the seeds mature the protective scales of the cones open up and the seeds are released. Page 8 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE General Characteristics  Their seeds are not enclosed within a fruit but are exposed on the surface of cone scales. Mature seeds lie exposed to the environment, thus they are regarded as naked.  They possess well-developed vascular tissues (xylem and phloem) for water and nutrients conduction.  Sporophyte is the dominant generation while the gametophyte generation is severely reduced to cones.  They lack flowers or fruits due to absence of an ovary, thus, reproduce by means of cones, hence, called flowerless plants.  Most are trees or shrubs, with significant secondary growth due to vascular cambium.  Pollination is solely wind-based. Male gametes (pollen) are conveyed to the ovule cone by means of pollen tube to effect fertilization.  Most are evergreen, retaining their leaves year round, though some are deciduous (example larches).  There are eight (8) orders of which 4 have become extinct (they are only known from their fossils because no representative are known to have survived to the present day) and the remaining four have living representatives. They include Cycadofilicales, Bennettifales, Pentoxylales, Cordaitales (all extinct), Cycadales, Coniferales, Ginkgoales and Gnetales. Order: Cycadales (Cycads or Cycadophyta) a. They have nearly 300 species and 11 genera of Cycads. Examples – Cycas circenalis and C. revolute (a Japanese spp). b. They primarily grow in tropical and sub-tropical regions where they are useful in outdoor landscaping. Cycads don’t grow outdoors in regions with harsh winters. Page 9 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE c. The stem is woody, un-branched, erect and palm-like, aan also bears a crown of pinnate leaves and small dry leaves arranged at the top with long tap roots. d. Male gametes (pollen) are borne at the apex of the plant which bears microsporophylls while, female gametes (Ovules) are borne on the upper surface of megasporophylls. e. Individual cycad plant produce either female cones or male cones but not both, hence, they are are dieocious. f. Pollination by wind or insects and the ovule grows into a seed after fertilization. Order: Coniferales a. Largest order represented by six families, 51 genera and 500 species, examples Pines, Cedars, and Hemlocks b. The most numerous and widespread of the gymnosperms; and are among the largest trees. c. They are cone-bearing woody trees and shrubs and most of them are found at higher altitudes. d. Mostly ever-green (do not drop their leaves in the autumn) with needle- like leaves that reduce water loss during dry season. e. Trees are heterosporous (produce two different kinds of cones) and are the major source of timber as well as paper. f. Male pollen cones and female seed cones are produced on the same tree although usually on separate branches. g. Pollination by wind or dispersed by seed eating birds or mammals. h. Fertilized ovules become winged seeds. i. Seeds mature in the second year and dispersed in the third year after fertilization. Page 10 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE Pinus ovuliferous scale (megasporophyll) bearing two winged seeds Order: Ginkgoales a. Has one genus and one species, Ginkgo biloba being the only surviving species of a once large group of plants. Many of its relatives became extinct as a result of an ancient global warming event that occurred about 206million years ago. b. Ginkgo trees grow as tall trees often reaching over 30m with leaves shaped like fans (with parallel venation). c. They are deciduous (losing their leaves during autumn). d. Their pollen and ovules are on separate trees and the pollen are transferred from male to female via wind action. e. Combines a vegetative structure like that of conifers, with primitive structures including a motile male gamete, like those of cycads. f. Native to southwest China and ornamental worldwide. Order: Gnetales a. Three families, 3 genera and 71 species, example Gnetum sp. b. Highest evolved group amongst the Gymnosperms that comprises of unusual plants that share certain features with angiosperms. c. Their vascular tissues include vessels in addition to tracheids, as do those of most angiosperms, (in contrast vascular tissues of other gymnosperms contains only tracheids). d. Flower is more advanced with Perianths present (petal and sepal). e. Pollination id by wind. Page 11 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session)  Students are allowed to reproduce for their own use NOT FOR SALE f. Some of them have a kind of double fertilization, a process that is also characteristics of angiosperms (but double fertilization in flowering plant differs). g. Seeda are with two cotyledon (dicot type).  They are Heterosporous i.e. form two types of spores: i. Microspores – the male gametes (pollen pairs) borne on microsprophyll. ii. Megaspores – the female gametes (ovule) borne on megasporophyll. Young sporophyte Mature sporophyte Megasporophyll Microsporophyll Seed Female cone Male cone Meiosis Embryo Endospore Megaspore Female Microspore Male Gametophyte gametophyte Ovule (egg) Sperm (pollen grain) Zygote Fertilization Pollination Life Cycle of a Gymnosperm (Pine tree cone) Angiospermae/Angiosperms (Flowering Plants) Fossil records indicated that angiosperms suddenly became abundant in the early cretaceous in a great variety of forms and have since then formed the dominant vegetation on the earth. General Characteristics  They produce seeds enclosed in fruits and have over 250, 000 species.  Comprise almost 90% of all land plants and virtually all domesticated plants.  They are the largest evolved group of plants, are widely distributed and thrive well in different ecological conditions.  They may be classified as: Hydrophytes, Mesophytes and Xerophytes Page 12 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE  They may be classified based on their morphology as herbs, shrubs and trees, with some being climbers or twinners e.g. Pothos.  Mostly are autotrophs but some parasitic varieties have been identified (examples Cuscuta and Loranthus).  They may be annuals, biennials or perennials.  They lack antheridia and archegonia, complexity of the sporophyte and reduction of the gametophyte.  Plant is differentiated into root, stem, and leaves.  Vascular bundles (conducting tissues) show highest degree of development.  Xylem consists of vessels and trachieds and phloem consists of sieve tube and cambium cells.  They bear flowers in which male and female gametes and spores develop.  Plant may be hermaphrodites or unisexual (being either monoecious or dioecious).  Pollination takes place mainly through insects and wind, which is subsequently followed by fertilization.  The male gametophyte (pollen grain) bears two male gametes while female gametophyte bears only one female gamete or egg cell.  One of the male gametes of the pollen-tube fuses with the egg-cell of the embryo-sac to form a zygote (oospore) which quickly grows into embryo. The other male gamete fuses with the two polar nuclei (in the female gametophyte) which gave rise to endosperm. This is known as double fertilization (a unique feature of the angiosperm)  The ovule and the ovary grow into seed and fruit respectively.  Roots may be tap root system formed from the radials or adventitious roots which are secondary in origin.  Plant bears two types of buds; Vegetative (which forms leaves and Reproductive (which forms flowers). Page 13 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session) Students are allowed to reproduce for their own use NOT FOR SALE  Leaf is a flattened structure, green in colour due to the presence of chloroplast which is the site for photosynthesis. Veination could be parallel or reticulate (network veination).  Based on the number of cotyledons in the seeds, angiosperms are divided into 2 groups, namely: 1. Monocotyledons 2. Dicotyledons Character Monocotyledons Dicotyledons Leaf Parallel veination Reticulate veination Stem Vascular bundles scattered, Ring of vascular bundles. anatomy cambium absent, no secondary cambium present giving rise to growth secondary growth Root Adventitious root (secondary in Tap root system (primary root) morphology origin) from the base of the destroyed primary root. Root Vascular bundles more than 5, no Vascular bundles 2 – 5 and anatomy secondary growth vascular cambium formed and giving rise to secondary growth Seed Embryo has one cotyledons Embryo has two cotyledons morphology Flower Parts usually in threes. Parts mainly in fours or fives. Often wind pollinated Often insect pollinated Examples Grasses, Orchids, Lilies, maize Pea, Rose, Buttercup, Dandelion Page 14 of 14 Faculty of Life Sciences BIO102 Lecture Note (2023/2024 Session)