Unit 6. Plants: General Characteristics and Reproduction

General Characteristics of Plants

UNIT 6. PLANTS1. GENERAL CHARACTERISTICS · Multicellular eukaryotic organisms o Autotrophic o PHOTOSYNTHESIS: produce energy and organic matter for: o The plant o Other organisms

Plant Structure: Thallophytes and Cormophytes

1.1. PLANTS STRUCTURE: THALLOPHYTES AND CORMOPHYTES THALLOPHYTES (without differentiated tissues): o Very simple organisation that do not have true leaves (PHYLLOIDS), stems (CAULOIDS) or roots (RHIZOIDS) o Cells are not specialised (they do not have tissues) but perform different functions.

Thallophyte Parts

PARTS Sporangium (Structure with spores) Phylloid Cauloid Rhizoids Mosses and liverworts OCauloid. It's a false stem that holds the phyllodes. · Sporangium. It is the structure that contains the spores, one of the reproductive forms of the plant. Phylloids. They are false leaves, but perform photosynthesis. Rhizoids. They are the false roots that fix the plant to the ground.

Cormophytes: Differentiated Tissues

1.1. PLANTS STRUCTURE CORMOPHYTES (With differentiated tissues): o More complex organisation with specialised cells. o Root, stem, leaves. o Pteridophytes and spermatophytes (phanerogams).

Cormophyte Parts

PARTS Stomata Leaves Stem Conductive vessels RootLeaves. They are laminae that are born in certain areas of the stem. Leaf cells perform photosynthesis. With this process the plant obtains the energy it needs to manufacture its own food. · Stomata are small pores, mainly located in the underside of leaves, which the plant uses to exchange gases and water vapour with the air. The underside is the side underneath the leaf. It usually has a paler colour. O O The stem. It is formed by an axis that branches out and serves as a base for leaves and flowers to implant. It contains conducting vessels. The upper surface of the leaf is exposed to sunlight. The root. It is the organ through which plants absorb water and mineral salts. In most cases it is underground, but there are also plants with aerial or underwater roots. Sieve elements Tracheids and vessel elements

The Root

THE ROOT O Part that grows generally inside the soil in the opposite direction of stem. O FUNCTIONS: O To absorb water and mineral salts (xylem sap) O To anchor the plant to the ground (stability and growing) O To store reserve substances (Ex: beetroot and carrot)Lateral root Primary root Zone of maturation Root hairs Zone of elongation Root tip Root cap Meristematic zone

The Stem

STEM o It is the aerial part of the plant formed by an axis that branches out. · FUNCTIONS: o Support of the leaves: so that they receive more light and supports flowers and fruits. o Transport of substances: It has conductive vessels Tracheids and vessel elements-> XYLEM: they conduct xylem sap( water and mineral salts) from root to leaves. > Sieve elements-> PHLOEM: transport phloem sap (produced in photosynthesis) from leaves to the rest of the plant.Apical bud Axillary bud Internode Node NODES: where branches and leaves grow INTERNODES: which are the zones between two nodes. BUDS are the shoots of the stem. TERMINAL or APICAL BUDS are responsable for the longitudinal growth. AXILLARY BUDS from which new branches, leaves and flowers grow sideways.

Leaves

LEAVES o They are usually flat and green organs and grow from the trunk or the branches. Stomata 0 H 4 O Upperside Underside Veins Apex (leaf tip) O FUNTIONS: O PHOTOSYNTHESIS O GASEOUS EXCHANGE O TRANSPIRATION (loss of water) Midrib (main vein) Blade Margin Petiole (Leafstalk) STOMATA: small pores, mainly located in the underside of leaves. Functions: to exchange gases and water vapour with air.

Stomata Structure

STOMATA occlusive cell stoma chloroplasts open closed

Leaf Characteristics

Number of blades Simple Pinnately compound Palmate compound Trifoliate compound Type of nerves Single-veined Parallel-veined Pinnate Palmate Shape Acicular Lanceolate Elliptic Ovate Hastate Dentate Serrate Entire Edge of the blade 2L Incised Split Lobed

Vital Functions in Plants

Nutrition

2. VITAL FUNCTIONS IN PLANTS NUTRITION O NUTRIENT UPTAKE: Ø Water and mineral salts (raw sap) from the soil through their roots. They are transported from roots to leaves through the xylem. > CO2 enter through stomata. o PHOTOSYNTHESIS: chloroplasts, chlorophyl, sunlight, inorganic compounds-> organics (elaborated sap). o TRANSPORT: elaborated sap is dristibuted to every cel through the phloem. O WASTE ELIMINATION: to eliminate useless or harmful substances. Ø TRANSPIRATION: the excess of water absorbed through the roots and O2 from photosynthesis are expelled into the atmosphere through the stomata.

Photosynthesis Process

PHOTOSYNTHESIS water + mineral salts + CO2 + sunlinght glucose + O2 light leaf water cel carbon dioxide sh amista oxygen oxygen water D chloroplasts chloroplasts carbon dioxide thylakoidsPHOTOSYNTHESIS takes place in the leaf, inside the chloroplast that contains chlorophyll, a pigment that captures solar energy. Thanks to this energy, the xylem sap (water + mineral salts) that arrives to the leaf through xylem and CO2 that enters through stomata (both are inorganic matter) are transformed into phloem sap (glucose=organic matter). This phloem sap is transported to every part of the plant through the phloem and O2 is released.

Interaction Function: Tropisms and Nastic Movements

INTERACTION FUNCTION Tropisms Nastic movements Slow, permanent and directional growth responses Quick, temporary and non-directional responses Positive: growth toward the stimulus Negativos: growth away from the stimulus Gravitropism gravity Phototropism Hydrotropism Light Water/humidity Seismonasty Physical contact Photonasty Light

Reproduction Function: Asexual Processes

REPRODUCTION FUNCTION ASEXUAL PROCESSES Asexual reproduction SPORES BULBS TUBERS RHIZOMES EX: Ferns Mosses Underground buds Underground stems Underground stems EX: Onions, garlic, leeks, tulips EX: Potatoes, tiger nuts EX: Lilies, ginger, callas

Reproduction Function: Sexual Processes

REPRODUCTION FUNCTION SEXUAL PROCESSES 6. Its cells begin to divide and a new plant is formed, which is independent from its progenitors. 1. Gametes are found in the sexual organs located in the flowers. 5. The seed germinates. 4. The seed, which contains the embryo, falls in a suitable and humid place. 3. The seed is enclosed in the fruit. 2. Flowers are fertilised and the seed is formed inside the fruit, which protects it and facilitates its dispersion.

Classification of Plants

3. CLASSIFICATION OF PLANTS Plants Non-flowering plants Flowering plants Gymnosperms Liverworts I Without fruit I Without conducting vessels I With developed conducting vessels Bryophytes Spermatophytes- Angiosperms I With fruit I With developed conducting vessels Ferns I With developed conducting vessels Pteridophytes Mosses I With very simple conducting vessels

Non-Flowering Plants (Seedless Plants)

Non-flowering plants (seedless plants) Spores to reproduce · 3.1. BRYOPHYTES · LIVERWORTS · MOSSES · 3.2. PTERIDOPHYTES · FERNS

Bryophytes: Liverworts and Mosses

3.1. BRYOPHYTES They do NOT form FLOWERS/SEEDS. LIVERWORTS: without conducting vessels MOSSES: with very simple conducting vessels Nutrients move between cells by diffusion. They reproduce by PROPAGULES All their parts absorb water and mineral salts -> they live in very humid environments. Maximum height: 20 cm Propagule

Bryophyte Reproduction

3.1. BRYOPHYTES: REPRODUCTION O ALTERNATING REPRODUCTION: with two forms in their life cycle: o GAMETOPHYTE-> sexual reproduction o SPOROPHYTE-> asexual reproduction

Moss Structure and Life Cycle

MOSS STRUCTURE · Filament with a capsule on the end producing spores. . When spores are ripe, they are dispersed. They will germinate and form a new gametophyte. Capsule Sporophyte Spores Seta Phylloids · Produce gametes . It is the most durable form. Gametophyte Cauloid RhizoidGermination Capsules Spores The spore generates rhizoids that fix the plant to the ground and develop gametophytes. Male gametophyte Male gametes Female gametophyte The sporophyte produces the spores and the cycle is closed. Gametophytes generate gametes. Female gametes The sporophyte grows on the female gametophyte. The zygote divides and the sporophyte develops. · Zygote O

Pteridophytes: Ferns

3.2.PTERIDOPHYTES: FERNS With developed conducting vessels. Without flowers or seeds. PARTS Fronds Sori Developing fronds Rhizome Roots . Live in shady and damp places · Maximum height 1.5m · PARTS: · RIZHOME: horizontal stem · FRONDS: big leaves subdivided into PINNAE: small leaves · SORI: clusters of SPORANGIA on the underside of the pinnae. · SPORANGIA produce spores (asexual reproduction)

Pteridophyte Reproduction

3.2.PTERIDOPHYTES: FERNS o ALTERNATING REPRODUCTION: with two forms in their life cycle. Both generations are independent plants: o SPOROPHYTE: the most visible part of the plant. ASEXUAL REPRODUCTION: spores o GAMETOPHYTE: smaller and shorter= llamado PROTHALLIUM. SEXUAL REPRODUCTION: sexual organs that produce gametesSporophyte It is formed by a horizontal stem from which small and numerous roots start growing downwards, while fronds grow upwards. On the underside of the fronds we can find the sori, which are clusters of sporangia. When spores are ripe, the sporangium opens and spores fall to the ground. With proper conditions, another heart- shaped plant with a thallus structure develops: it is called gametophyte. Sori · Sporangium O Gametophyte Spores It develops rhizoids to attach to the soil and to nourish. Fronds uncoil spirally in a characteristic way. They are shaped like a feather and have two different surfaces: the upper side and the underside. Sporophyte The horizontal stem is a rhizome. The small and numerous roots come from it and grow downwards. Male and female sexual organs are developed in the gametophyte. The fertilisation of the gametes forms the zygote. The growth of the zygote gives rise to a new sporophyte, which appears coiled in its first moments.

Plants with Flowers and Seeds: Spermatophytes or Phanerogams

3.3. PLANTS WITH FLOWERS AND SEEDS: SPERMATOPHYTES or PHANEROGAMS o They reproduce SEXUALLY through seed formation o TWO GROUPS depending on their capacity to form FRUITS around their seeds: o GYMNOSPERMS: Without fruit o ANGIOSPERMS: with fruit

Gymnosperms

GYMNOSPERMS are FLOWERING, vascular plants whose SEEDS are NOT SURROUNDED by FRUITS, but instead look BARE · CHARACTERISTICS: o They are woody and mostly trees. o Evergreen plants and leaves with acicular shape (PINES) or scale- like (CYPRESSES) o Unisexual flowers (a flower has stamen or pistil) group together in inflorescences. o They often carry out anemophilous pollination. o Different groups: o Ginkgo and cycads: the most primitive groups o Conifers (PINES and FIR): the most widely-known group. Inflorescences called CONES or PINECONES. Once fertilisation has completed inside the female inflorescence, it transforms into a cone with seeds (PINE NUTS), inside it.