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