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Transcript
Honors Biology Chapter 10 Plant Reproduction John Regan Wendy Vermillion Insert Ch opening photo 10-1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10.1 Sexual reproduction in flowering plants • Alternation of generations – Flowering plants have 2 multicellular stages in their life cycle • Diploid sporophyte stage alternates with the haploid gametophyte stage • The sporophyte produces haploid spores by meiosis – spores develop into gameotphytes • The gametophyte produces gametes by mitosis – after fertilization the cycle returns to the sporophyte stage 10-2 Alternation of generations in flowering plants • Fig 10.1 10-3 Sexual reproduction in flowering plants cont’d. • Overview of plant life cycle – Flower- reproductive structure of angiosperms – The diploid sporophyte is the predominant stage • The sporophyte bears flowers; flowers produce 2 spore types – Megaspore-develops into female gametophyte-embryo sac – Microspore-develops into the male gametophyte-pollen grain • Pollination-deposition of pollen onto female flower parts – Pollen grain contains 2 sperm cells; pollen grain digests a tube that the sperm swim through to reach the embryo sac – Embryo sac contains an ovum; fertilization occurs and an embryo develops – Embryo sac develops into a seed which can be enclosed in a fruit- aids dispersal – When seed germinates a new sporophyte develops 10-4 Sexual reproduction in flowering plants cont’d. • Flowers – Typical flower has 4 whorls of modified leaves attached to a receptacle 1. Sepals-green leaflike structures that protect bud 2. Petals-attract pollinators 3. Stamens-male structures – consist of anthers and filaments 4. Carpel-female structure – consists of a stigma, style, and an ovary 10-5 Anatomy of a flower • Fig 10.2 10-6 Sexual reproduction in flowering plants cont’d. • Flowers, cont’d. – A complete flower has all parts-petals, sepals, stamens, and carpels flower can have a single carpel or multiple • Each carpel contains the ovules – Bisexual (perfect) flowers- have both stamens and carpels – Unisexual (imperfect) flowers-have either stamens or carpels • Dioecious plants- have either staminate or carpellate flowers on one plant • Monoecious plants- have both staminate and carpellate flowers on the same plant 10-7 Sexual reproduction in flowering plants cont’d. • Production of the male gametophyte – Microspores produced in anthers – Microspore mother cell divides by meiosis to produce 4 haploid microspores – In each, the haploid nucleus divides mitotically and then an unequal cytokinesis occurs – the 2 cells are enclosed in a pollen grain; the larger is the tube cell, the smaller is a sperm cell – The sperm cell divides again to form 2 sperm 10-8 Life cycle of a flowering plant • Fig 10.5 10-9 Sexual reproduction in flowering plants cont’d. • Pollination – Transfer of pollen from an anther to a receptive stigma of a carpel – Pollen grain contains 2 cells- generative cell, tube cell • Tube cell grows into pollen tube • Generative cell ÷ into 2 sperm cells 10-10 Sexual reproduction in flowering plants cont’d. • Production of the female gametophyte – Embryo sac ÷3x into 8 nuclei as the functional nucleus divides 4 times by mitosis – One small cell becomes the egg – Double fertilization- one sperm fertilizes the egg and it becomes the embryo(2n); the other fertilizes the central cell to form the triploid (3n) endoderm – Endosperm becomes the food source for the embryo inside the seed 10-11 Pollination • Fig 10.6 10-12 Development of a eudicot embryo • Fig 10.7 10-13 Growth and development cont’d. • Development of the eudicot embryo, cont’d. – Embryo changes from a ball of cells to a heart-shape – Cotyledons-embryonic leaves appear – Embryo next becomes torpedo-shaped, and the root tip and shoot tip become visible – Epicotyl-portion of embryo between the cotyledons that contributes to shoot development – Hypocotyl-portion below the cotyledons that contributes to stem development – Radicle-contributes to root development 10-14 Growth and development cont’d. • Monocots versus eudicots – Eudicots have 2 cotyledons, monocots have one – In monocots, the cotyledons do not store food • cotyledon absorbs food from endosperm and passes it to the embryo • In eudicots the cotyledons store the nutrients the embryo uses – Endosperm disappears as the cotyledons take up the nutrients 10-15 Growth and development cont’d. • seed dispersal- the function of fruits is to disperse seeds – seed dispersal • • • • • Attach to fur of animals or clothing Ex: burrs Passed in feces of bird or mammals Ex: berries Dispersed when buried or stored by animals Ex: acorns Wind-winged or plumed seeds Ex: maple seeds Float-coconut 10-16 Growth and development cont’d. • Germination of seeds – – – – Germinate in response to specific environmental conditions Requires both inhibitor and stimulator substances Mechanical stimuli also may be required in some Uptake of water causes seed coat to burst 10-17 Common garden bean seed structure and germination • Fig 10.9 10-18 Growth and development cont’d. • Eudicot versus monocot germination – Eudicots • Cotyledons shrivel and degrade • Epicotyl produces immature leaves- plumule • young shoot is hook-shaped as it emerges through the soil – Monocots • Cotyledon does not have a storage function • Plumule and radicle are protected by sheaths called the coleoptile and the coleorhiza respectively • Plumule and radicle burst through the sheaths when germination occurs • Young shoot is straight, not hooked 10-19 Corn kernal structure and germination • Fig 10.10 10-20