The Plant Kingdom topic 9pages 83-87 • The Plant Kingdom: An Introduction - Learning Activity • Amazing little food factories for themselves and most terrestrial food chains • Retain stem cells ( meristems) for growth through out their life. • Meristem cells are small and reproduce by mitosis and cytokinesis
Plant ClassificationBryophytes • Mosses: have no true roots, only structures similar to root hairs called rhizoids.
More on bryophytes • Mosses have simple leaves and stems.
Liverworts are bryophytes • Liverworts consist of a flattened thallus.
Bryophytes Maximum height is 0.5 ,meters Reproductive structures: Spores are produced in a capsule. The capsule develops at the end of a stalk
Life Cycle of a Moss animation • Spores produced in capsule, found on a stalk.
Filicinophytes • Ferns have • a rhizome with adventitious roots, • Leaves • short woody stems. • The leaves are usually curled up in buds and are often pinnate ( divided up into pairs of leaflets).
Filicinophytes / Ferns • Maximum height is 15 meters • Spores are produced in sporangia, usually on the underside of leaves • All have vascular roots, leaves & non-woody stems.
Pinnate leaves • There is a main nerve, called midrib, from which the other nerves derive. Reproductive strategies: • Cell Cycle & Cancer Animation • Life cycle Flifecycle2
Coniferophytesconifers • Conifers are shrubs or trees with roots, leaves and woody stems. The leaves are often narrow with a thick waxy cuticle
conifers • Maximum height is 100 meters • Seeds are produced. The seeds develop from ovules on the surface of the scales of female cones. Male cones produce pollen
Angiospermophytesflowering plants • Flowering plants are very variable but usually have roots, leaves and stems. The stems of flowering plants that develop into shrubs and trees are woody.
angiosperms • Maximum height is 100 meters. Seed are produced. The seeds develop from ovules inside ovaries. The ovaries are part of flowers. Fruits develop from the ovaries, to disperse the seed.
Flowers. Pistil is female part and stamen is male • Animations • Animations
Photoperiodic control of flowering • Short day plants • Long day plants • Studies have shown that it is not the length of time there is light but dark • Go to study guide page 87 • Flower growers can manipulate light to produce flowering plants year round
Photoperiodism, Gravitropism, and Thigmotropism AP Biology Unit 5
Photoperiodism • How a plant responds (with respect to flowering) to the relative amount of light (“photoperiod”) • In reality, plants are responding to the relative amount of night. Slide 2 of 15
Photoperiodism is a biological response to a change in relative length of daylight and darkness as it changes throughout the year. • Hormones such as phytochrome, and others not yet identified, probably influence flowering and other growth processes.
Photoperiodism: Types of Plants • 3 different types of plants: • “Short Day” flower when days are short, nights are long (Ex. poinsettias, chrysanthemums) • “Long Day” flower when days are long and nights are short (Ex. Spinach, Radish) • “Day Neutral” flowering does not depend on length of day or night (Ex. tomato) Images taken without permission from http://www.fernlea.com/xmas/pix/poinsettia.jpg, and http://www.illinoiswildflowers.info/weeds/plants/garden_radish.htm Slide 3 of 15
Question… • Poinsettias are short day plants– how could nurseries make sure they bloom just before Christmas? • Control the amount of light and dark they experience Slide 4 of 15
Phytochromes • Plants absorb light via blue-light photoreceptors and phytochromes (Pr and Pfr). • Pr and Pfr play a significant role in the flowering and germinating responses • Experiments into the control of flowering time Slide 5 of 15
Phytochromes • Germination and flowering occurs in response to red and far-red light • effects of both lights are reversible • Pr and Pfr are isomers (alternate forms) • red light (660 nm) activates Pr to become Pfr • far-red light (730 nm) activates Pfr to become Pr Slide 6 of 15
Flowering • Pfr • inhibits flowering in short day plants • promotes flowering in long day plants • Sunlight consists of quite a bit of red light, not much far red light • During the day, which form of phytochrome is in? • Pfr Slide 7 of 15
Flowering • At sunset, most of the phytochrome is in the Pfr form • During the night, Pfr gets converted back into Pr or breaks down • Whether a plant flowers or not depends on the amount of Pfr left (which relates to the amount of night) Slide 8 of 15
Phototropism/gravitropism • http://bcs.whfreeman.com/thelifewire/content/chp38/3801s.swf
Auxins • Tutorial 38.2 Went's Experiment • Plant Hormones
Experiments Predict what will happen in each of these experiments. Normal young shoot Tip removed from shoot Tip covered with a foil cap Tip removed and replaced with an agar block containing auxin Tip removed and replaced on one side with a small agar block containing auxin
Applications of plant hormones Can you explain the use of hormones in each diagram. Click to reveal the answer. Fresh fruits are shipped around the world. Plant hormones are used to slow the ripening of the fruit, so they are just ripe as they reach the supermarket.
Applications of plant hormones Powder Can you explain the use of hormones in each diagram. Click to reveal the answer. When a gardener takes cuttings from a plant, the base of each cutting is first dipped into a rooting compound to stimulate the growth of roots. Many rooting compounds contain auxin.
Plants adapt to where they grow • Xerophytes - plants that are adapted to grow in very dry habitats. • Spines instead of leaves, to reduce transpiration • Thick stems containing water storage tissue • Very thick waxy cuticle covering stem, reducing water loss
Vertical stems to absorb sunlight early and late in the day but not at midday when the light is most intense • Very wide spreading network of shallow roots to absorb water after rains • CAM physiology, which involves opening stomata during the cool nights instead of during intense day heat
Hydrophyteswater plants • Air space in the leaf to provide buoyancy • Stomata in the upper epidermis of leaf is in contact with the air • Waxy cuticle on the upper surface but not on bottom surface • Small amounts of xylem in stems and leaves
Leaves • Tissues of leaves and their function
Xylem – brings water to replace losses due to transpiration
Phloem – transports products of photosynthesis out of leaf. (source to sink) • Both xylem and phloem are called the vascular system of plants. The vein is centrally located to be close to all cells.
Transport in phloem • Phloem is located inside leaves. Used to transport sugars, amino acids, and other organic compounds from photosynthesis. • Structures called sieve tubes do the transporting. • This is an active process requiring ATP • High concentration in sieve tubes of solute cause water to move in by osmosis
Translocation in phloem • Phloem tissue found throughout plants. • Links sources and sinks. • Sources = photosynthetic tissue • Sink = roots, fruits, seeds, and leaves • Sometimes sources turn into sinks and vice versa depending on plant needs.