School Science Lessons
Plants
2013-03-20
Please send comments to: J.Elfick@uq.edu.au
Table of contents
9.0.0 Plant kingdom
9.0.1 Plant kingdom experiments
9.7.0 Heterotrophic angiosperms, (Exp.)
9.6.0 Plant parts, (Exp.)
9.5.01 Seed-bearing plants, seed plants, Spermatophytes (gymnosperms and angiosperms)
9.0.0 Plant kingdom
9.1.0 Algae (seaweed, waterweeds), Spirogyra
9.2.0 Liverworts, liverworts, Phylum Hepatophyta, Hepaticae, Pellia. Marchantia
9.2.2 Hornworts, Phylum Anthocerotophyta, Anthoceros, Dendroceros, Felioceros, Notothyles, Phaeoceros
9.3.0 Moss, Phylum Bryophyta, Musci, Funaria, Polytrichum
9.3.2 Club moss, Phylum Lycopodiophyta, Lycophyta, Selaginella, Lycopodium
9.4.0 Ferns, Order Filicales, Phylum Pteridophyta, Pterophyta, Pteridium, Dryopteris
9.4.2 Horsetails, Phylum Equisetophyta, Equisetum
9.5.01 Seed-bearing plants, seed plants, Spermatophytes (gymnosperms and angiosperms)
9.5.0 Conifers, cone-bearing trees, Coniferophyta, Pinopsida, Phylum Pinophyta, pine
9.5.2 Gymnosperms
9.6.0 Flowering plants, angiosperms, buttercup, wallflower, groundsel, Phylum Magnoliophyta
9.6.01 Monocotyledons, (angiosperms), grasses, orchids, lilies palms, bulbs, corms, rhizomes, dendrobium, spinifex, iris
9.6.02 Dicotyledons, (angiosperms), herbs, shrubs and trees, buttercup, potato
9.6.03 Monocotyledons and dicotyledons, (angiosperms)
9.0.1 Plant kingdom experiments
9.2.1 Liverworts, liverworts, Phylum Hepatophyta (Hepaticae), Pellia, Marchantia
9.3.1 Moss, Phylum Bryophyta, Musci
9.4.1 Ferns, Order Filicales, Phylum Pteridophyta, (Pterophyta), Pteridium, Dryopteris
9.5.1 Conifers, gymnosperms, cone-bearing trees, (Coniferophyta, Pinopsida), Phylum Pinophyta, Pinus
9.6.0 Plant parts, (Exp.)
9.6.22 Corm, false stem (pseudostem) banana, taro
9.6.14 Creeping stems, moneywort (creeping jenny), ground ivy
9.6.20 Herbaceous dicotyledon stem, buttercup
9.6.6 Herbaceous dicotyledon stem, carnation
9.6.5 Herbaceous stem, forage legume alfafa, (lucerne)
9.6.7 Herbaceous monocotyledon stem, iris
9.1.4.1 Rhizome, ginger, iris
9.6.15 Runners, strawberry
9.6.18 Stem hooks, bramble (blackberry), rose
9.6.16 Stolons, currant, European gooseberry, banana
9.6.13 Terminal bud, linden tree (lime tree), beech, oak
9.6.8 Xeromorphic stem, spinifex
9.6.12 Twigs of trees in winter, horse chestnut, sycamore, linden tree (lime tree), beech, oak
9.6.21 Twining stem, climbing bean, yam
9.6.17 Woody stem, hawthorn
9.1.0 Algae (seaweed, waterweed)
9.1.1 Chlamydomonas, Sphaerella, (Haematococcus), green algae, Phylum Chlorophyta
9.1.5 Closterium, desmid, (Family Desmidiaceae), Phylum Chlorophyta
9.1.6 Ecklonia, Sargassum, brown algae, brown seaweed, kelps, Phylum Phaeophyta
9.1.9 Fucus, Ecklonia, brown seaweed, kelp
9.1.7 Hormosira, Cladophora, Dictyota, brown algae, common seaweed, Family Fucaceae, Phylum Phaeophyta
9.1.2 Pleurococcus, (Protococcus), Phylum Chlorophyta
9.1.3 Spirogyra, Ulothrix, Zygnema, Phylum Chlorophyta
9.1.8 Vaucheria, yellow-green algae, Xanthophyceae, (xanthophytes), Phylum Tribophyta
9.1.4 Volvox, Phylum Chlorophyta
9.7.0 Heterotrophic angiosperms
Experiments
9.7.1 Bird's nest orchid
9.7.5 Bladderwort
9.7.4 Butterwort
9.7.2 Insectivorous plants, pitcher plant, Venus fly trap
9.7.8 Mycorrhizal plants
9.7.6 Parasitic angiosperms, toothworts, broomrapes, sandalwood, devil's twine, olax, sarracenia
9.7.7 Parasitic angiosperms, dodder, mulberry, mistletoe
9.7.3 Parasitic angiosperms, sundew
9.1.1 Chlamydomonas, Sphaerella, (Haematococcus), green algae, Phylum Chlorophyta
See diagram 9.39: Chlamydomonas, Sphaerella, (Haematococcus)
Look for the cilium, contractile vacuole, cytoplasm, eye spot, cup-shaped chloroplast, nucleus, and cell wall. Find Chlamydomonas as a bright green "water bloom" in freshwater pools, tanks and stagnant water. Chlamydomonas is unicellular, grows quickly and is about 10 microns in diameter, and has motile gametes.
Put cheese and the white of a hard-boiled egg in a glass container. Add garden soil and washed sand. Fill the container with rainwater and stand it in diffuse sunlight. After a week, the water in the glass container may turn green with Chlamydomonas. Put a drop of the culture water on a microscope slide, apply a coverslip, and examine the culture under low power. Observe the rapid rhythmic rolling movements of Chlamydomonas. Irrigate with iodine solution and observe the cell wall, basin-shaped chloroplast, eye spot and storage granules.
Sphaerella, (Haematococcus), is another unicellular alga that occurs in stagnant pools. It has a brick-red pigment in the vacuoles and so may form brown masses on trees and even brown rain and snow. If cultured in a jar of water, it is attracted by low intensity light.
9.1.2 Pleurococcus, (Protococcus), Phylum Chlorophyta
See diagram 9.40: Pleurococcus (Protococcus)
Pleurococcus (Protococcus), causes red snow.
Stain with iodine solution. Observe the cell surrounded by the cell wall. Look for the nucleus, cytoplasm, and the large irregular-shaped chloroplast. Note division into two daughter cells that will become round and separate from each other. Scrape a green encrustation from a piece of damp wood or bark of a tree. Mount in water and examine under low power. The spherical green structures are single cells of the alga Pleurococcus. Look for colonies of cells.
9.1.3 Spirogyra, Ulothrix , Zygnema, Phylum Chlorophyta
See diagram 9.41: Spirogyra cell | See diagram 9.41.1: Chloroplasts of Spirogyra and Ulothrix
Look for the nucleus, cytoplasm, cell wall, and spiral chloroplast.
Spirogyra and Zygnema are unbranched filaments with cylindrical cells arranged end to end. Find these bright green, freely floating algae as clumps on the surface of ponds as "pond scum". Keep them in water from the original site. Spirogyra chloroplasts are in spiral bands. Zygnema has two star-shaped chloroplasts. These filamentous algae live as blue-green patches in rain puddles, on the moist walls of greenhouses and at the water's edge in dirty ponds and pools. Observe its threadlike growth. Lift out a piece of green scum with attached mud and transfer it to a glass container with some water in which it was growing. Keep it in a room in diffuse sunlight. Examine the algae in a drop of the original water to see the blue-green filaments with cross walls.
9.1.4 Volvox, Phylum Chlorophyta
See diagram 9.42: Eudorina, Gonium, Pandorina, Volvox
Volvox, is a coenobium of ciliated cells forming a hollow sphere with a rolling motion. Volvox looks like a hollow sphere colony of Sphaerella. Each Volvox is composed of many flagellate cells each similar to a Chlamydomonas, about 1000-3000 in total, interconnected by plasmodesmata and arranged in a hollow sphere (coenobium). Each cell has beating cilia that cause the Volvox to roll along through the water. Inside a Volvox colony may be daughter colonies. Reproduces asexually from large gonidia cells and sexually from male antheridia and female oogonia cells.
9.1.5 Closterium, desmid, (Family Desmidiaceae), Phylum Chlorophyta
See diagram 9.43: Closterium
Look for the nucleus, pyrenoids, and chloroplasts in two "semi-cells". Closterium and other desmids occur in acidic clean water, e.g. ponds and drainage ditches. Culture them in the water in which they were living. Examine the crescent-shaped cells. Desmids contain barium sulfate crystals and they indicate clean, unpolluted water with acid pH.
9.1.6 Ecklonia, Sargassum, brown algae, brown seaweed, kelps, Phylum Phaeophyta
See diagram 9.44: Ecklonia
Ecklonia maxima, red algae, kelp, sea bamboo
Look for the fronds, stem, and holdfast. The Sargasso Sea in the Atlantic Ocean is famous for huge areas of the floating brown algae, Sargassum.
Examine a brown seaweed found between low and high tide marks. Observe the holdfast for anchorage, the stem and the expanded frond containing chlorophyll for photosynthesis and the yellow-brown pigment fucoxanthin.
9.1.7 Hormosira, Cladophora, Dictyota, brown algae, common seaweed, Family Fucaceae, Phylum Phaeophyta
See diagram 9.45: Hormosira, Neptune's necklace, kelp | See diagram 9.45.1: Dictyota
Look for the repeated forking at the receptacles, inflated internodes form hollow bladders called receptacles, flask-shaped conceptacles sunken into the bladder wall that produce sperm and ova. Hormosira is a marine alga, also called sea grapes or bubble weed, that grows in the intertidal zone. Observe the holdfast and body like a string of hollow beads or grapes, receptacles. The bumps on the receptacles are the conceptacles, round little holes containing the sexual organs. At high tides, gas in the receptacles keeps the plant erect. At low tides, the exposed plant collapses but the tough leathery body protects it.
9.1.8 Vaucheria, yellow-green algae, Xanthophyceae, (xanthophytes), Phylum Tribophyta
Mount some fresh filaments. Observe the method of branching. Examine part of a filament under high power. Examine a prepared slide showing antheridia and oogonia.
9.1.9 Fucus, Ecklonia, brown seaweed, kelp
See diagram 9.44: Ecklonia seaweed
Fucus vesiculosus, kelp, bladderwrack, herbal remedy, Fucaceae
1. Examine a brown seaweed found between low and high tide marks. Observe the holdfast for anchorage, the stem and the expanded frond containing chlorophyll for photosynthesis and the yellowish pigment fucoxanthin. Examine a plant of Fucus as an example of a brown seaweed. Observe the disc shaped or branched holdfast, the stalk or stipe, and the expanded lamina showing thick midrib and wings. Note also the indentations at the tips of the thallus where the growing points are situated.
2. Observe the holdfast, stipe and fronds. If the specimen is Fucus vesiculosus, note also the bladders that give buoyancy. Cut a transverse section across a vegetative branch and mount and examine under low power. Note the differentiation into limiting layer, cortex and medulla. Examine prepared slides of transverse sections cut through male and female conceptacles. Observe the antheridia, oogonia and paraphyses.
9.2.0 Liverworts, liverworts, Phylum Hepatophyta (Hepaticae), Pellia, Marchantia
See diagram 9.46.2: Marchantia life cycle | See 9.46.1: Marchantia
Liverworts have alternation of generations because they have a flat leafy (n, haploid) gametophyte and have a delicate stalk (seta) (2n, diploid) sporophyte that dies after spore dispersal.
9.2.1 Liverworts, liverworts, Phylum Hepatophyta (Hepaticae), Pellia, Marchantia
1. Collect plants of Pellia in the early spring. Observe the leafy gametophyte with rhizoids at its base and the capsule or sporogonium. Note the presence of dark green globular capsules just behind the growing points of some thallus branches. Also, note small warty prominences further back from the tip and either side of the midrib. These prominences are old antheridia cavities, now empty. Dissect out a sporogonium, noting the short seta. Crush the capsule into a drop of water. Observe the wall with its characteristic thickenings, the spores and the elaters. Cut a transverse section of the thallus, mount in water and note the structure, similar to the lamina of Fucus but attached to the soil with hair-like rhizoids.
2. Collect Pellia plants in the early summer. Observe the presence of antheridia and cut sections through the thallus where they occur. Note also involucres just behind the tips of some branches and cut longitudinal sections through these to see the archegonia.
Look for the thallus, gemma cups, rhizoids, sperm with two flagella, male thallus, antheridium, female thallus, and archegonium.
Liverworts are the most lowly land plants with single-celled rhizoids and no clearly-differentiated stem and leaves. They grow in moist shady habitats on wet rocks or near shallow streams, usually clumped together to save moisture. The plant is the gametophyte generation, a broad branching thallus. Together the plants look like little leaves clumped together and attached to the damp soil by hair-like rhizoids. The antheridia produce swimming sperm that fertilize an ovum in the archegonium to form the zygote that grows into the sporophyte. The sporophyte has no chlorophyll and remains a sort of parasite with no connection to the soil but attached to the archegonium. It releases spores that develop into the next gametophyte generation. Marchantia reproduces rapidly by vegetative buds produced in gemma cups. The sexual organs, the antheridia and archegonia are formed on different plants. Riccia is a floating liverwort. Collect plants from moist sheltered places, e.g. behind waterfalls, in cooler periods of the year.
9.2.2 Hornworts, Phylum Anthocerotophyta, e.g. Anthoceros, Dendroceros, Felioceros, Notothyles, Phaeoceros
Hornworts have a simple gametophyte and a long horn-like sporophyte.
9.3.0 Moss, Phylum Bryophyta, Musci
Mosses have an upright or creeping gametophyte with leaves arranges spirally. The sporophyte has a tough seta that persists after spore dispersal. In open country, moss grows mostly on the north side of trees in the Northern hemisphere and on the south side of trees in the Southern hemisphere. Mosses grow 1-10 cm tall in clumps or mats in shady or damp locations. Some grow on trees, fences and walls. Mosses have multicellular rhizoids and distinct stems and leaves. Mosses have an upright or creeping gametophyte with leaves arranged spirally. If the sex organs are developed on different plants, as with Dawsonia, the antheridia are attached to a cup-like receptacle at the apex of the male plant. The antheridia burst to release sperm that use their two cilia to swim in rain water to the archegonia at the apex of the female plants and fertilize the ova. The zygote grows vertically into the sporophyte that remains attached to the female plant and consists of a long stalk, seta and a capsule containing the sporogonium. The mature capsule will release very light spores to be dispersed by the wind and grow into the next gametophyte generation.
9.3.1 Moss, Phylum Bryophyta, Musci
Catharinea, Dawsonia, Funaria, Mnium, carpet moss, Polytrichum, haircap moss, Sphagnum, peat moss, Stricta herbal medicine
See diagram 9.47.1: Funaria, sporogonium | See diagram 9.47.2: Moss life cycle | See diagram 9.47.3: Dawsonia, male and female plant
1. Examine capsules of Funaria or other mosses at different stages of maturity and note the peristome and the method of liberation of spores. If you fix a cut off capsule in wax, you can examine the peristome under low power. Breath on the capsule to show the hygroscopic movements of the peristome teeth.
2. Collect protonema of Polytrichum from hedgerows or on the soil in flower pots. Polytrichum spores germinate to form a filamentous stage called a protonema. Later, buds form on the protonema to grow into the moss plant. Polytrichum often mingles with Vaucheria, but Polytrichum is septate. Observe the green filaments with transverse septa and the brownish rhizoids with oblique septa. Observe buds on the green filaments and young plants in various stages of development.
3. look for the male and female plant, female plant with attached sporogonium, leaves, stem, rhizoids, sporogonium capsule, sporogonium seta.
4. Collect common woodland mosses usually found in compact colonies or cushions in damp shady places. Some grow on the damper side or south side of tree trunks and fence posts. Observe the erect stems, small leaves, and the rhizoids that attach the plant to the soil. Look for terminal cups, sexual organs, and tubular capsules that contain asexual spores. Some tufts of plants bear rosette-like antheridia cups containing spores. Dissect out the contents of one of these into water and note the structure of the antheridia and paraphyses, sterile hairs or filaments that bear the spore-making structures, the sporangia. The archegonia cups that house the ovum are less conspicuous, so you may have to dissect more than one apex to find an archegonium.
9.3.2 Club moss, Phylum Lycopodiophyta, (Lycophyta), Selaginella, Lycopodium
See diagram 9.49: Selaginella
1. Look for the Selaginella plant, cone, scale leaves, lateral leaves, rhizophores, microsporangia containing many microspores, and megasporangium containing four megaspores. The club mosses have club-shaped cones that bear spores and are known as ‘fern allies’. Plants of the Selaginella genus, spikemoss, are small prostrate plants with four rows of small leaves on the axis. They live in damp places and Selaginella kraussiana and Selaginella martensii are grown in greenhouses. The Selaginella plant is a sporophyte bearing microsporangia and megasporangia in the same cone. A microsporangium produces microspores to be dropped onto damp soil and later eject a swimming sperm. The larger megaspangium produces megaspores to be dropped onto the soil, germinate in rainy weather, and produce a females prothallus with an ovum inside. The ovum is fertilized by the sperm to form a zygote that grows into the next sporophyte generation. Both types of spores have a tri-radiate ridge from origin in the tetrads following meiosis. Collect the microspores and megaspores from a ripe cone and scatter the spores on moist absorbent paper. Observe the development of young sporophytes.
2. In Lycopodium note the presence of definite cones. Examine the sporangia, both externally and by cutting sections of the cones.
9.4.0 Ferns, Order Filicales, Phylum Pteridophyta, (Pterophyta), Pteridium, Dryopteris
Ferns are vascular plants with xylem and phloem, true leaves, but no seeds. They are mostly terrestrial but Marsilea lives in swamps. Azolla and Salvinia are floating ferns. The stag's horn is a common epiphyte in rainforests. The asexual phase, the sporophyte, is the large fern that develops spores in sporangia. The sexual phase, the gametophyte, develops the sexual organs. It is an insignificant little plant like a little flat leaf, the size of a fingernail.
9.4.1 Ferns, Order Filicales, Phylum Pteridophyta, (Pterophyta), Pteridium, Dryopteris
See diagram 9.48.0: Dryopteris | See diagram 9.48.2: Pteridium frond, leaflet, rhizome | See diagram 9.48.3: Pteridium prothallus, sporophyte | See diagram 9.48.4: Fern life cycle
Look for the sori under a leaf, compound leaf or frond, coiled young leaf, rhizome, and roots.
1. Examine Dryopteris, wood fern. Note the rhizome and adventitious roots, stem and compound leaves, fronds. Note the sori (singular: sorus) under the recurved fronds where spores are formed. Dryopteris has rounded sori. Pteridium has long sori along the margins of the pinnules.
2. Cut a transverse section of a pinnule of Dryopteris to pass through a sorus. Observe the tissues of the leaf, the placenta, sporangia in various stages of development in the indusium.
3. Dehiscence of fern sporangia Pteridium
Scrape some ripe sporangia into a drop of glycerine on a slide. The glycerine withdraws water from the annulus cells and thus causes the opening of the sporangia. You can slow the movements of the annulus with glycerine. Scrape other sporangia on to a warm slide and observe the annulus movements under the microscope.
4. Fern prothallus Pteridium
To grow fern prothalli, place a soaked flower pot inside a larger one, packing the space between with wet sphagnum or peat. Allow a mature frond bearing a sorus to dry on a piece of paper and then scatter the spores so obtained on the inner surface of the small flower pot. Stand the pots in an inch or so of water and cover the top of the pots with a sheet of glass. Green prothalli will soon appear, and you can observe successive stages in their development. Observe the archegonia and also the liberation of sperms from the antheridia. Young sporophytes will develop if you water the prothalli after they show archegonia.
9.4.2 Horsetails, Phylum Equisetophyta, Equisetum
Equisetaceae, Equisitales, Equisetopsida, Sphenophyta, scouring rushes
Equisetum arvense, horsetail, zinnkraut, pewter plant, herbal medicine, garden herb, (fossil: Calamites), herbal remedy.
9.5.0 Conifers, gymnosperms, cone-bearing trees, (Coniferophyta, Pinopsida), Phylum Pinophyta, Pinus
Spruce, larch, redwood, podocarp, hoop pine, juniper, Juniperus, Podocarpus, Taxus
Conifers are seed-bearing plants with ovules on the edge of an open sporophyll. The sporophylls are arranged in cone-like structures. Conifers are pyramidal or conical trees with long straight stems that taper to an apical growing point, the leader. The almost horizontal branches bear narrow needle-shaped leaves. The original tap root dies leaving shallow roots that let the tree be blown over by storms. Smaller roots have no root hairs but have a sheath of fungus that penetrates into the root epidermis. Small microspore cones at the ends of branches produce microspores, pollen grains. Large megaspore cones are made up of leaf-like sporophylls that contain the ova. The fertilized ova develop to form seeds released when the woody cone opens. Most conifers produce woody cones by lignification of the seed-bearing sporophylls, but Juniperus, Podocarpus and Taxus have soft fruit.
9.5.1 Conifers, gymnosperms, cone-bearing trees, (Coniferophyta, Pinopsida), Phylum Pinophyta, Pinus
Spruce, larch, redwood, podocarp, hoop pine, juniper, Juniperus, Podocarpus, Taxus
See diagram 9.50: Pinus | See diagram 9.50.1: Pine cone
Look for a microspore cone, pollen grain, pollen tube, microsporophyll, microspores (pollen) megasporophyll, micropyle, ovule, megaspore, and bract.
1. Examine twigs of Pinus in summer. The twigs should show evidence of at least three years' growth. Observe the structure of purely vegetative twigs, the position and structure of seed cones of varying age, the position and structure of staminate cones.
2. Examine the male and female cones of Pinus. Dig up some shallow roots and examine the mycorrhiza under the microscope Dissect first year, second year and third year seed cones and note their general structure. Note the seeds lying naked on the cone scales.
3. Remove a megasporophyll from a first year cone and look for the two megasporangia (ovules) on the upper surface. The bract scale is on the lower surface.
4. Examine the structure in longitudinal section under high power.
5. Examine a sporophyll from a second year cone in the same way.
6. Examine a third year cone. Remove a megasporophyll and note the seeds with their wings attached. Cut a longitudinal section through a seed and examine under low power.
7. Dissect a staminate cone and note the form of the microsporophylls (stamens). Crush one of them into a drop of glycerine and examine the pollen grains under high power. Examine transverse and longitudinal sections of staminate cones.
8. Examine the structure of the current year stem and the older stems by means of transverse and longitudinal sections. Examine the tracheids, the sieve tubes, the medullary rays and the resin canals.
9. Cut a transverse section of a leaf.
9.5.2 Gymnosperms, naked seed plants, have ovules and seeds on surface of leaf-like sporophylls. They include Coniferophyta, Cycadophyta, Ginkgophyta, Gnetophyta, but nowadays the term is not used in plant classification.
9.6.0 Flowering plants, angiosperms, buttercup, wallflower, groundsel, Phylum Magnoliophyta
Angiosperms have seeds enclosed in an ovary, the flowering plants, but nowadays the term is not used in plant classification.
1. Angiosperms have the following characteristics:
1.1 The ovules are enclosed in a carpel. The carpel with three parts, the stigma where pollen germinates, the style that allows pollen tubes to reach the ovary, and an ovary that encloses the ovules and where fertilization occurs. The three parts together are called the pistil.
1.2 Double fertilization produces a zygote that becomes the embryo plant and endosperm nutritive tissue in the seed for the developing plant embryo.
1.3 Stamens with pollen sacs produce pollen.
1.4 Phloem tissue consisting of sieve tubes and companion cells for the transport of nutrients and hormones.
2. The shoot system consists of stem, leaves and buds. The leaves are attached to the stem at the nodes. The internode is the part of the stem between two nodes. The leaf is attached to the stem by a leaf base. The petiole, leaf stalk, joins the leaf base to the expanded lamina, the leaf blade. The leaf venation, pattern of veins, is net-like. This reticulate venation is typical of dicotyledons. At the apex of the shoot is the terminal bud with the growing point protected and covered by young unexpanded leaves. The nodes and young leaves are telescoped together. Elongation of the short internodes in this region results in growth in length of the shoot. Axillary buds in the axils of leaves are also embryonic shoot systems that can grow into lateral branches, stems bearing leaves, or they may just remain dormant. Inflorescences, clusters of flowers, can be produced from axillary or terminal buds.
Examine the external features of a herbaceous flowering plant, e.g. buttercup, wallflower, groundsel.
9.6.01 Monocotyledons, grass (cereals), bamboo, sugar cane, maize (corn)
See diagram 9.52: Monocotyledon, grass
Monocotyledons include arrowroot, banana, coconut palm, canna, ginger, onion, orchids, pineapple, screw-pine, sisal, taro, yam. Monocotyledons have the following characteristics: 1. The embryo has one cotyledon. 2. They are mostly herbaceous plants, except palms and the larger bamboo. 3. Tap roots rarely occur. 4. The vascular bundles are closed, cambium is absent, and secondary thickening is rare. 5. The leaves have parallel veins with simple cross connections. The midrib is absent, 6. The floral parts are usually in threes. A typical floral formula is as follows: P 3+3 A 3+3 G (3). 7. Many monocotyledons have bulbs or corms, or rhizomes.
1. Cut stems transversely, e.g. grass (cereals), bamboo, sugar cane, maize (corn). Note the similarities in the cross-sections. Note the tubes of vascular bundles scattered through the pith.
2. Examine a grass and note flowers (inflorescence), ligule, leaf blade, parallel veins, leaf sheath, node, internode, fibrous roots,
9.6.02 Dicotyledons, geranium, tomato, willow
See diagram 9.53: Dicotyledon, (diagrammatic)
Dicotyledons have the following characteristics: 1. The embryo has two cotyledons. 2. They are mostly woody plants. 3. Tap roots are common. 4. Vascular bundles are open, cambium is present, and secondary thickening is common. 5. The leaves have a network of veins and a midrib. 6. The floral parts are usually in fives so a typical floral formula is K5 C5 A5 G5. 7. Dicotyledons include mango, kapok, hemp, sunflower, sweet potato, cress, pumpkin, cassava, avocado, peas and beans, cotton, fig, nutmeg, eucalypts, passion fruit, sesame, pepper, coffee, citrus, tomato, potato, cocoa, tea, jute, and many trees and shrubs.
1. Examine a dicotyledon and note terminal bud, axillary bud, branch or lateral shoot, roots, root tips, stem, 1st node, 2nd node, axil, 3rd node, leaf, flower, and flower stalk or pedicel.
2. Cut stems transversely, e.g. geranium, tomato, willow. Note a bright green layer, the cambium layer, under the outside layer of the stem. Note tubes of vascular bundles arranged in a ring about the central, or woody, portion of the stem.
3. Compare monocotyledon stems with dicotyledon plant stems. Cut stems downwards under water then put the cut ends in an ink solution. Later, cut the stems transversely to see which cells are involved in the upward movement of water
9.6.5 Herbaceous stem, forage legume alfafa, (lucerne)
Herbaceous stems have growth from the cambium limited to one season or part of one season, or lacking. They have no distinctive anatomical structure, but some features are typical of monocotyledons others of dicotyledons. Vascular bundles in stems are collateral with endarch xylem. Alfalfa, (lucerne), Medicago sativa, Fabaceae, is a perennial herbaceous plant grown for fodder.
Observe the following tissues:
1. The epidermis is covered by a cuticle.
2. The cortex is narrow compared with the cortex of the root and consists of collenchyma as four corner strands forming longitudinal ridges on the stem and parenchyma.
3. The outer part of the cortex contains chloroplasts.
4. The single peripheral ring of discrete bundles without active cambium.
5. The vascular tissue arranged as discrete collateral bundles with phloem to the outside, xylem to the inside and cambium between the xylem and phloem.
6. The pith consisting of parenchyma in the centre of the stem.
7. The parenchyma rays between the vascular bundles.
9.6.6 Herbaceous dicotyledon stem, carnation
Carnation is a perennial herbaceous plant with a complete vascular cylinder. Observe the following: epidermis covered by a cuticle, cortex comprising chlorenchyma and sclerenchyma, stele is a continuous ring comprising phloem, cambium, xylem, endarch (the first formed xylem next to the pith) medulla parenchyma.
9.6.7 Herbaceous monocotyledon stem, iris
Observe the widely spaced discrete vascular bundles arranged peripherally in two rings or scattered throughout the transverse section. Cambium is not usually formed and most vascular bundles have a sclerenchyma sheath. In monocotyledons with scattered bundles there is no distinction of ground tissue into cortex and medulla. Where the vascular strands are confined to the periphery of the stem there is either a medulla cavity or a distinct parenchyma medulla.
9.6.8 Xeromorphic stem, spinifex
See: Spinifex stem, T.S. (from EBOT, University of Sydney)
Spinifex, (Triodia sp), .is a grass that grows on sand dunes. It has a prostrate stem with roots and shoots at the nodes. The anatomical structure is a typical monocotyledon stem with scattered bundles and no cambium. Observe the following: epidermis covered by cuticle, vascular bundles scattered throughout the parenchyma ground tissue, a fibre sheath around each vascular bundle, a continuous band of sclerenchyma in the peripheral region where the sheaths merge to give rigidity to the stem.
9.6.12 Twigs of trees in winter, horse chestnut, sycamore, linden tree (lime tree), beech, oak
See diagram 9.51.2: Horse chestnut shoot
Note the terminal bud, the leaf scars with associated axillary buds, the ring of bud scale scars and the lenticels. Dissect a terminal bud. Arrange the scales and young foliage leaves in series. The scales are leaf bases. A large scar between two terminal buds shows the position occupied by an inflorescence in the previous spring. The formation of an inflorescence by the terminal bud leads to the growth of the branch being carried on by the two axillary buds immediately below. Examine stages in the opening of the buds in spring.
9.6.13 Terminal bud, linden tree (lime tree), beech, oak
Examine the apparently terminal bud and note that at the side of a leaf scar another small scar has been formed by the withering and falling off of the original terminal portion of the shoot. So the apparently the terminal bud is really an axillary bud. Dissect a bud and arrange the parts in a series. Note the pair of outer scales followed by pairs of inner scales that have a small foliage leaf between them. The bud scales are stipules. Note the opening of the buds in the spring and note that the stipules soon fall from the foliage leaves.
9.6.14 Creeping stems, moneywort (creeping jenny), ground ivy
Note the long, recumbent habit of the stem, the absence of scale leaves and the position of the adventitious roots.
9.6.15 Runners, strawberry
Study the formation of new plants. The short stem, the crown, produces runners, stolons, from it axillary buds. The stolons are modified shoots. The second node on the stolon touches the ground and forms a new plant.
9.6.16 Stolons, currant, European gooseberry, banana
See diagram 51.13.1: Banana stool
Note the curved stems and how adventitious roots are given off from where the stem touches the ground. Note exactly where the new adventitious shoots form.
9.6.17 Woody stem, hawthorn
See diagram 9.57: Wood sections 1 | See diagram 9.57.1: Wood sections 2 | See diagram 9.57.2: Piece of cut wood
Stems have four functions: 1. Transport of food from leaves to roots 2. Transport of water and plant nutrients from roots to leaves 3. Support of leaves and branches 4. Store food.
Note the position of the thorns on the hawthorn stem. Look also for larger examples, which bear foliage leaves. Compare the structure of a twig of gorse with that of the hawthorn.
9.6.18 Stem hooks, bramble (blackberry), rose
Examine the hooks on the stem and petioles of the bramble or rose. Compare them with thorns. Hooks are modified hairs. Thorns are modified branch shoots.
9.6.20 Herbaceous stem, buttercup
See diagram 9.51: Buttercup | See diagram 9.59.1: Pumpkin stem
Cut by hand TS and LS sections of young buttercup stems.
9.6.21 Twining stem, climbing bean, yam
See diagram 63.4: Yam twining stem
Swollen rounded underground stem, i.e. stem tuber, e.g. yam.
Twining tendrils: white bryony, passion fruit, sweet pea, garden pea.
Virginia creeper has adhesive tendrils.
9.6.22 Corm, false stem (pseudostem) banana, taro
See diagram 51.5: Banana corm | See diagram 51.1: Cultivated and "village" banana plant | See diagram 62.7: Taro corm | See diagram 9.82: Gladiolus corm
1. The true stem of the banana plant is an underground stem, a rhizome. The swollen stem base is the corm with very short internodes. The corm makes shoots that grow into branches or other corms. New plants come from these shoots. Suckers grow from the dormant buds called "eyes" on the corm. Each sucker formed is higher than the corm it came from. If the land is sloping, the suckers are usually formed on the uphill side. If left alone, generations of banana plants will gradually move up a hill.
2. The taro corm is an underground stem swollen with stored starch. Like other stems it has these parts: The growing point or a shoot apex. Many leaves joined to the shoot apex. Leaf scars are seen as circular marks that go around the corm. Axillary buds form just above the place where the leaf was joined to the stem. The axillary buds can grow into little corms or "cormlets" (cormels). The cormlets can grow into suckers.
9.7.1 Bird's nest orchid
Note the matted underground stems and the fleshy roots. Sections of the latter will show the endotrophic mycorrhiza.
9.7.2 Insectivorous plants, pitcher plant, Venus fly trap
See diagram 9.66.3: Nepenthes
Butterworts and sundews live on wet acid soils where there is a lack of nitrogenous compounds. Keep plants damp in the laboratory with the original soil left around the roots.
9.7.3 Sundew
Drosera rotundifolia occurs in bogs. Observe the creeping rhizomes, rosette arrangement of the leaves and short petioles. In the field, touch the leaf to get the tentacles to respond as if trying to trap an insect. Mount tentacles and examine under low power. Note the stalk and the glandular head.
9.7.4 Butterwort
Note the rosette leaves with incurved margins of the butterwort and the sticky nature of the upper surface. Mount a piece of leaf with the upper surface uppermost and examine under low power. Note the stalked capturing glands and the sessile digestive glands.
9.7.5 Bladderwort
The bladderwort lives in pools of brackish water. This plant has no roots. The leaves are very finely divided. The flowers project above the water. Note the shape of the bladder and the presence of hairs at the orifice. Open several bladders and look for the remains of animal prey.
9.7.6 Parasitic angiosperms, toothworts, broomrapes, mistletoe, sandalwood, devil's twine, olax, sarracenia
Rafflesia has the largest flower in the world.
See diagram 9.53.11: Mulberry mistletoe
See sections across a branch in TS or LS and through the haustorium longitudinally. Greenhouses of botanic gardens often contain examples of tropical carnivorous plants
9.7.7 Dodder, Cuscuta
See diagram 9.53.12: Dodder haustorium penetrating host mistletoe
Observe dodder plants coiling around the stems of clover, heather, gorse and nettle, Urica. Note the manner in which it coils around its host, its reduced, scale-like leaves and its pink flowers. Notice the absence of chlorophyll and explain the parasite's method of nutrition in view of this. Examine the haustoria and cut a transverse section of the stem of the host plant in the region of a haustorium. Notice the type of host tissue that the haustoria cells penetrate.
9.7.8 Mycorrhizal plants
The mycelia of certain fungi assist in absorbing of plant nutrients, especially poor soils. The relationship between the fungus and the plant is mutualism. Some fungi live just outside the roots of woody species, e.g. Eucalyptus, oaks, pines, olives. Other fungi penetrate the root and live between the cells in many grain plants. The myco-heterotrophic orchids, Dipodium variegatum and Dipodium hamiltonianum are colonized by Russulaceae fungi.
9.6.03 Monocotyledons and dicotyledons
See diagram 9.53: Dicotyledon, parts of a plant | See diagram 9.52: Monocotyledon - parts of a plant, grass
Table 9.6.0
Monocotyledons Dicotyledons
Embryo has one cotyledon Embryo has two cotyledons
Mostly herbaceous plants, except palms Mostly woody plants
Tap roots are common Tap roots are rare
Vascular bundles closed, cambium absent, secondary thickening rare Vascular bundles open, cambium present, secondary thickening common
Leaves have parallel veins with simple cross connections, midrib is absent Leaves have network of veins, midrib is present
Floral parts usually in threes, typical floral formula: P 3+3 A 3+3 G3.
 Floral parts usually in fives, typical floral formula: K5 C5 A5 G5
Include grasses, orchids, lilies, palms. Many have bulbs, corms, rhizomes Most trees and shrubs