1. Interactions in Plants
What are the processes that plants use to maintain homeostasis?
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2. Transport of water and nutrients
Plants must meet their basic needs
What specialized structures help them survive? Do plants respond to their environment?
Vascular plants have elaborate systems for transporting water and nutrients, and organic compounds
Roots, stems, and leaves work together to move these materials throughout a plant
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3. Roots and Xylem
Roots absorb water and dissolved minerals such as phosphorus, nitrogen, and potassium from the soil
The materials are then transported upward in a plant by specialized transport tissue called xylem
Xylem is made of elongated cells that are connected end to end, like small pieces of tubing
Transpiration is he evaporation of water from plant leaves
Tension created during the process of transpiration provides the driving force that pulls water and other minerals upward
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4. Water escapes a plant through tiny openings in the leaves called stomata
Stomata are surrounded by guard cells that act as a gatekeeper for the stomata
When the guard cells change shape, the stomata open or close
When the stomata are open, water escapes through evaporation
This causes tension within the plant, which pulls water upward through the Xylem
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Stomata

5. Phloem Phloem is also part of the transport system in plants
Phloem is specialized tissue that takes in the glucose and other organic nutrients produced during photosynthesis and transports these to the rest of the plant
Phloem is made of elongated cells that help move materials throughout the cell
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Phloem

6. Stomata gas exchange
Stomata are also the site of gas exchange in plants
During photosynthesis, plants take in carbon dioxide and release oxygen through the stomata in their leaves
Stomata are closed at night to reduce water loss
During the day, they are open to allow the exchange of gases
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7. Plants that grow in dry climates have small narrow leaves to minimize water loss
Needles on cactus plants and evergreen trees are actually leaves
Needles contain fewer stomata
Have a low surface to volume ratio, which helps reduce damage from drought conditions or heavy snow
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Specialized Leaves

8. Land plants alternate between two types od generations: haploid and diploid
Switching between the two stages is called alternation of generations
In the haploid generation, the plant produces male and female gametes by mitosis
The male gametes are the sperm, and the female gametes are the eggs
When they join, they form a zygote that begins the sporophyte generation (diploid generation)
Sporophyte produces haploid spores by meiosis, that then undergo mitosis
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Plant life cycle

9. Spores
Spores are often encased in a tough, outer casing that protects the genetic material inside the spore
Some spores are adapted to surviving harsh environmental conditions, germinating only when conditions have improved
Other spores are adapted to be very light, so they are carried long distances on the wind
Spores differ from seeds in that spores carry little nourishment inside the spore compared to seeds
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10. Reproductive Plant Structures – day 2
Plants have specialized cells for sexual reproduction
Gymnosperms have gametophytes in cones
Angiosperms have gametophytes inside flowers
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11. Angiosperm reproduction
Takes place through pollination, which is the transfer of pollen from one to another
Specialized pollen cells produce sperm cells that are contained within the pollen, pollen must land on the stigma in order for fertilization to take place
Fertilization happens when the sperm from the pollen travels from the stigma, down the style, then combines with the ova, in the ovaries
The diploid zygote will become a new sporophyte plant
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Angiosperm reproduction

12. Responses to stimuli
Homeostasis – process of maintaining a stable internal environment
Plants respond to changes in their internal and external environments
Stimuli are anything that initiates a response of action in an organism
Plants respond to external stimuli including light, heat, and moisture
Plants respond to internal stimuli like water and nutrient levels within the cells
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13. Plant motion
Plants are sessile, meaning they cannot move from place to place
Plants have a limited range of motion toward and away from specific stimuli called tropism
Phototropism
Plants need to move and grow toward the sun
Thigmotropism
Some plants respond to touch – vines, ferns
Gravitropism – Geotropism –
Plants respond to gravity by growing roots downward into the soil, and stems away from the soil
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14. Auxin is a plant hormone that controls plant growth and development
Produced in shoot tips and travel downward into the ground
Cause root formation and make new buds grow
Inhibit the growth of lateral buds, causing plants to grow tall and not out
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Auxins

15. Cytokinin Also promote plant growth
Hormones produced in growing roots and in developing fruits and seeds
Stimulate cells division to promote growth
Unlike auxins, they cause plants to grow outward, rather than upward, by promoting lateral buds
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Cytokinin

16. Response to other gases
Farmers use ethylene gas to speed up the ripening of fruits such as bananas and tomatoes
Some plants release noxious gases that warn neighboring plants of a possible predator
Cabbage and tobacco plants release a gas when pests feed on their leaves, and it induces pest resistance in other parts of the plant and in neighboring plants
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Response to other gases