Interactions in Plants What are the processes that plants use to maintain homeostasis? This Photo by Unknown Author is licensed under CC BY-NC

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 This Photo by Unknown Author is licensed under CC BY

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 This Photo by Unknown Author is licensed under CC BY

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 This Photo by Unknown Author is licensed under CC BY-SA Stomata

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 This Photo by Unknown Author is licensed under CC BY-SA-NC Phloem

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 This Photo by Unknown Author is licensed under CC BY-SA

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 This Photo by Unknown Author is licensed under CC BY-SA Specialized Leaves

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 This Photo by Unknown Author is licensed under CC BY-SA Plant life cycle

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 This Photo by Unknown Author is licensed under CC BY-SA

Reproductive Plant Structures – day 2 Plants have specialized cells for sexual reproduction Gymnosperms have gametophytes in cones Angiosperms have gametophytes inside flowers This Photo by Unknown Author is licensed under CC BY-SA

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 This Photo by Unknown Author is licensed under CC BY-SA Angiosperm reproduction

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 This Photo by Unknown Author is licensed under CC BY-SA

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 This Photo by Unknown Author is licensed under CC BY-SA

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 This Photo by Unknown Author is licensed under CC BY-SA Auxins

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 This Photo by Unknown Author is licensed under CC BY-SA-NC Cytokinin

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 This Photo by Unknown Author is licensed under CC BY-SA Response to other gases