Plant Growth, Reproduction, and Response (Session 5-6) PDF

22.1 Plant Life Cycles 22.1 Plant Life Cycles Plant life cycles alternate between producing spores and gametes....

22.1 Plant Life Cycles 22.1 Plant Life Cycles Plant life cycles alternate between producing spores and gametes. A two-phase life cycle is called alternation of generations. – haploid phase – diploid phase Plant – alternates between these two phases reproduction and SPOROPHYTE PHASE respiration fertilization meiosis GAMETOPHYTE PHASE A sporophyte is the diploid multicellular stage in the life cycle of a plant. 22.1 Plant Life Cycles 22.1 Plant Life Cycles KEY CONCEPT The spore-producing plant is the mature sporophyte. All plants alternate between two phases in their life – sporophyte phase is diploid cycles. – begins with fertilized egg – spores produced through meiosis The gamete-producing plant is the mature gametophyte. – gametophyte phase is haploid – begins with spore – gametes produced through mitosis 22.1 Plant Life Cycles 22.1 Plant Life Cycles Life cycle phases look different among various plant – A fern gametophyte, or prothallus, produces sperm groups. and eggs. Nonvascular plants have a dominant gametophyte phase. gametophyte (1n)) – moss gametophytes look like green carpet – moss sporophytes shoot up as stalklike structures sporophyte (2n) capsule spores (1n) rhizoid – A zygote forms on the prothallus, growing into the gametophyte (1n) sporophyte. 22.1 Plant Life Cycles 22.1 Plant Life Cycles The sporophyte is the dominant phase for seedless The sporophyte is the dominant phase for seed plants. vascular plants. – pine trees are typical seed plant sporophytes – Fern spores form in sacs, sori, on underside of mature – female spores produced in female cones sporophytes (fronds). – male spores produced in male cones – male spores develop into pollen grains, the male gametophytes sporophyte (2n) – female spores develop into female gametophytes that produce eggs – sperm from pollen travel down pollen tube toward egg – fertilized egg develops into embryo – ovule develops into protective pine seed sori 22.1 Plant Life Cycles 22.2 Reproduction in Flowering Plants The sporophyte is the dominant phase for seed plants. Flowers contain reproductive organs protected by specialized leaves. Sepals and petals are modified leaves. – Sepals are outermost layer that protects developing flower 22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants KEY CONCEPT – Petals can help to attract animal pollinators Reproduction of flowering plants takes place within flowers.  22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants A stamen is the male structure of the flower. Flower Parts stamen filament anther – anther produces pollen grains – filament supports the anther 22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Complete and Perfect Flower The innermost layer of a flower is the female carpel. Flower stigma carpel style ovary – stigma is sticky tip – style is tube leading from stigma to ovary – ovary produces female gametophyte  22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Complete and Perfect Flower Simple fruit Monocot Flower The pericarp is the tissue that develops from the ovary wall of the flower and surrounds the seed to protect it in environments apart from the parent plant. 22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Aggregate fruit Parts of a fruit An aggregate fruit is a fruit that develops from a single flower, The two main functions of fruit are to prevent the seeds from drying and to disperse the seed. The fruit may be either fleshy or dry. Fleshy fruits, like the but the flower has more than tomato or apple, hold juices that prevent the seeds from drying until they are one ovary, and the ovaries mature. Fleshy fruits also serve to help disperse the seeds. join together as the fruit grows. A fruit that grows from The fruit is composed of three distinct layers: An outer skin or exocarp, a fleshy middle layer or mesocarp, and a hard, woody layer or endocarp just one flower that contains surrounding the seed. just one ovary, is not an aggregate fruit but a simple The mesocarp is the edible part of the fruit with a pulp rich in fatty acids, fruit. amino acids, and vitamins. In addition to seed protection and dispersal, the endocarp also plays an important role in sustaining and communicating with developing seeds.  22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Multiple fruit Flowering plants can be pollinated by wind or animals. Flowering plants are pollinated when pollen grains land on stigma. Wind pollinated flowers have small flowers and large amounts of pollen. Wind-pollinated flowers don't need to be attractive to insects, so they are usually small and do not produce nectar or have large colorful petals. Pollen grains of wind-pollinated flowers are produced in large quantities to make sure that at least some pollen grains reach the stigmas of other flowers and successful pollination takes place as many pollen grains are wasted. These pollen grains are light and hence are easily transferred to other flowers. 22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Animal pollinated flowers have larger flowers and less pollen. – many flowering plants pollinated by animal pollinators pollen grains A fruit that grows from just one flower that contains just one ovary, is a simple fruit. An aggregate fruit is a fruit that develops from a single flower, but the flower has more than one ovary, and the ovaries join together as the fruit grows. Multiple fruits, also called collective fruits, are fruiting bodies formed from a – pollination occurs as animal feeds from flower to flower cluster of fruiting flowers. – animal pollination is more efficient than wind pollination  22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants Fertilization takes place within the flower. Pollination occurs when a pollen grain lands on a stigma. Male gametophytes, or pollen grains, are produced in the anthers. – male spores produced in anthers by meiosis – each spore divides by pollen tube mitosis to form two sperm haploid cells – two cells form a stigma single pollen grain pollen grain – one cell from pollen grain forms pollen tube – other cell forms two sperms that travel down tube 22.2 Reproduction in Flowering Plants 22.2 Reproduction in Flowering Plants One female gametophyte can form in each ovule of a Flowering plants go through the process of double flower’s ovary. fertilization. – four female spores produced female gametophyte in ovule by meiosis – one spore develops into female gametophyte egg – female gametophyte contains seven cells – one cell has two nuclei, or polar nuclei sperm – one cell will develop into an egg polar nuclei ovule  22.2 Reproduction in Flowering Plants 22.3 Seed Dispersal and Germination Flowering plants go through the process of double KEY CONCEPT fertilization. endosperm Seeds disperse and begin to grow when conditions are favorable. – one sperm fertilizes the egg seed coat – other sperm unites with polar nuclei, forming endosperm – endosperm provides food supply for embryo embryo 22.2 Reproduction in Flowering Plants 22.3 Seed Dispersal and Germination Each ovule becomes a seed. Seeds begin to grow when environmental conditions are favorable. The surrounding ovary grows into a fruit. Seed dormancy is a state in which the embryo has stopped growing. – Dormancy may end when conditions are favorable. – While dormant, embryo can withstand extreme conditions.  22.3 Seed Dispersal and Germination 22.3 Seed Dispersal and Germination Germination begins the growth of an embryo into a Germination begins the growth of an embryo into a seedling. seedling. – water causes seed to swell and crack coat – water causes seed to swell and crack coat – embryonic root, radicle, is first to emerge – embryonic root, radicle, is first to emerge – water activates enzymes that help send sugars to – water activates enzymes that help send sugars to embryo embryo – embryonic shoot, plumule, emerges next – leaves emerge last 22.3 Seed Dispersal and Germination 22.3 Seed Dispersal and Germination Germination begins the growth of an embryo into a Once photosynthesis begins, the plant is called a seedling. seedling. – water causes seed to swell and crack coat – embryonic root, radicle, is first to emerge – water activates enzymes that help send sugars to embryo – embryonic shoot, plumule, emerges next  22.4 Asexual Reproduction 22.4 Asexual Reproduction KEY CONCEPT Humans can produce plants with desirable traits using Plants can produce genetic clones of themselves vegetative structures. through asexual reproduction. Vegetative propagation takes advantage of plants’ ability to reproduce asexually. Humans use one plant with desirable traits to produce many individuals. – cutting of leaves or stems may grow new roots – grafting joins the parts of two plants together to form a hybrid plant 22.4 Asexual Reproduction 22.5 Plant Hormones and Responses Plants can reproduce asexually with stems, leaves, or KEY CONCEPT roots. Plant hormones guide plant growth and development. Asexual reproduction allows a plant to make copies of itself. – Plants can grow a new part from a fragment of parent – occurs when piece of a stem, leaf, or root falls off parent plant – Plant regeneration refers to the physiological renewal, repair, or replacement of tissue in plants  22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Plant hormones regulate plant functions. Ethylene causes the ripening of fruits. Hormones are chemical messengers. – some fruits picked before – produced in one part of an organism they are ripe – stimulates or suppresses activity in another part – sprayed with ethylene to ripen when reach destination 22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Gibberellins are plant hormones that produce dramatic Cytokinins stimulate cytokinesis. increases in size. – final stage in cell division – ending seed dormancy – produced in growing roots, seeds, and fruits – rapid growth of young – involved in growth of side branches seedlings – rapid growth of some flower stalks  22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Auxins lengthen plant cells in the growing tip. Thigmotropism is a plant’s response to touchlike stimuli. – stimulates growth of – climbing plants and vines primary stem – plants that grow in direction of constant wind – controls some forms of tropism A tropism is the movement of plant in response to an environmental stimulus. 22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Plants can respond to light, touch, gravity, and seasonal Some plants have rapid responses not involving growth. changes. – Some responses protect Phototropism is the tendency of a plants from predators. plant to grow toward light. – Some responses allow – auxins build up on shaded side of plants to capture food. stem – cells on shaded side lengthen – causes stem to bend toward light  22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Photoperiodism is a response to the changing lengths of day and night. – triggers some plants to flower – triggers fall colors/winter dormancy of deciduous trees 5 1 22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses 7.6 RESPIRATION IN PLANTS ◼ Plants less active than animals → need lower energy requirement ◼ Gaseous exchange occur mainly in the leaves (large surface area to volume ratio) ◼ By simple diffusion through the stomata & the lenticels ◼ Gaseous exchange in the light ◼ Gaseous exchange in the dark 50 52  22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Gaseous Exchange in the Light Aerobic Respiration In Plants ◼ Gaseous exchange can be investigated in ◼ During photosynthesis, the [CO2] in the air space of the spongy layer falls below the the dark 0.04% Glucose + oxygen → carbon dioxide + water + energy C6H12O6 + 6O2 → 6CO2 + 6H2O + 2880 kJ/ mole ◼ CO2 in the atmosphere → stomata → spongy layer ◼ Carried out throughout the day & night ◼ O2 in the cells →stomata → atmosphere ◼ In the light, photosynthesis is faster than ◼ Both respiration & photosynthesis occur respiration. ◼ The rate of both processes depends on the ◼ CO2 produced is quickly used up by light intensity photosynthesis 53 55 22.5 Plant Hormones and Responses 22.5 Plant Hormones and Responses Gaseous Exchange in the Anaerobic Respiration in Plants Dark ◼ Occurs when O2 absent – alcoholic fermentation ◼ Respiration alone is taking place ◼ Occurs in certain situations – flooding, initial ◼ Less O2 inside the spongy layer than stages of germination outside Glucose → ethanol + carbon dioxide + energy ◼ O2 from atmosphere → lenticels → C6H12O6 → 2C2H5OH + 2CO2 + 210 kJ/ mole spongy layer ◼ Excess of Ethanol is toxic, as it alters Enzyme ◼ CO2 from cell respiration → lenticels → Activity in Anaerobic Respiration in Plants. atmosphere 54 56  22.5 Plant Hormones and Responses Respiration & Photosynthesis ◼ Respiration is the reverse of photosynthesis ◼ Respiration uses the product of photosynthesis, photosynthesis uses the product of respiration 57 22.5 Plant Hormones and Responses Compare & Contrast Respiration & Photosynthesis RESPIRATION PHOTOSYNTHESIS SIMILARITIES ◼ Both are metabolic processes DIFFERENCES A process of catabolism A process of anabolism Occurs in all living cells Occurs in cells containing chloroplast / chlorophyll Take place in absence & presence Require light of light Uses glucose & oxygen Uses carbon dioxide & water Produces CO2 & H2O Produces glucose & O2 Cell loses weight Cell gains weight Chemical energy → heat + ATP Solar energy → chemical energy 58