Plant Growth and Development - Germination.pptx

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z Plant Growth and Development: Germination z Seeds  All seeds contain an embryo and have their own food supply.  The embryo consists of an epicotyl, cotyledons, radicle, and a se...

z Plant Growth and Development: Germination z Seeds  All seeds contain an embryo and have their own food supply.  The embryo consists of an epicotyl, cotyledons, radicle, and a seed coat  The epicotyl is the portion of the stem that becomes the leaves and stem of the plant z Seeds  The cotyledons are the seed leaves used for food storage.  The radicle is the young embryonic root and root tip.  The hypocotyl is the first to emerge from the seed. z Seed Classification  Seeds of monocot plants have 1 cotyledon.  Seeds of dicot plants have 2 cotyledons. z Dicot Seeds  Dicots include: soybeans, peanuts, peas, carrots, clover. z Monocot Seeds  Monocots include: corn, wheat, rye, oats, barley, and rice z Seed Germination  Factors affecting seed germination  Moisture  Temperature  Oxygen  Light z Moisture  A seed must have an 85% of moisture for germination to occur.  Imbibition is what triggers the germination process.  Once the germination process begins, a dry period or lack of water will cause the delay of the developing embryo. z Temperature  Temperature affects both the germination rate and the germination percentage.  Germination is faster when temperatures are higher.  The optimum temperature for most plant seeds to germinate is 70 degrees F to 85 degrees. z Oxygen  Oxygen is required for cellular respiration, a process necessary for converting stored carbon to carbon dioxide. z Light  Seeds of some plants need exposure to light before they will germinate.  Other seeds require darkness in order to germinate.  Some are not influenced by light or darkness.  Seeds that are light sensitive have a photoreceptor pigment called rhabdom. z Assistive Processes  Scarification – physical or chemical treatment done in order to weaken the seed coat.  Dry Stratification – pre- treating the seeds to simulate winter conditions in order to germinate. z Adverse Conditions  Conditions that may affect the viability and germination of seeds include:  Mechanical injury  Excess water  Improper storage  Disease  Not enough soil z The Germination Process  Water Absorption  Emergence of radicle  Plant growth z Water Absorption  The seed absorbs water and air.  This causes the seed to grow and multiply in size  Results in cellular processes to begin which converts stored starch to energy usage z Emergence of Radicle:  The seed coat ruptures permitting the root or radicle to emerge and grow downward to anchor the plant

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