Plant Growth Requirements

1. Plant Growth Requirements http://expage.com/page/waxnsteel Topic 2019 By Torey Birchmeier http://199.212.16.18/msc/as/index_e.html

2. Major Factors for Plant Growth • Temperature • Light • Moisture • Carbon Dioxide • Hormones http://home.earthlink.net/`bob4mvg/Time_n_Temperature.htm

3. Temperature • As temperature increases, reaction rates increase • ie-Photosynthesis is slower at lower temperatures: however the rate increases up to a cerain point as the temperature goes up • Plant growth functions such as absorption of minerals and water are determined by temperature

4. Temperature • Plants have an optional temperature range at which they function best • Plants have a minimum temperature tolerance below which the plant may be injured or killed • Monocots have an advantage because the growth point remains below the ground • Dicots’ growing point is pushed above the ground and do not tolerate fluctuating temperatures or frost

5. Temperature http;//expage.com/page/waxnsteel • Sun scald can occur at high temperatures • High temperatures cause desiccation or may may directly kill protoplasm of cells • Plants should be selected according to the growth conditions and climate of the area • An exception is the greenhouse where temperature conditions can be controlled

6. Light effects plants based on its quality, intensity and duration. • Quality • The major source of light is the sun • Normal plant growth requires white light or sunlight • Chlorophyll absorbs the red and blue portions of the light spectrum. Leaves are green, since the chlorophyll reflects green light

7. Quality • Light is important and must contain important wavelenghts • These wavelengths are represented by the rainbow http://204.97.147.10/card/paper.htm

8. Light Intensity provides energy for photosynthesis • Rate of photosynthesis is effected by water, carbon dioxide and sunlight • In the absence of light, plants will grow until there food reserves are exhausted • This growth will be elongated and abnormal

9. Light Intensity • Phototropism is the tendency to grow in the direction of the greatest light intensity • Plants vary in the intensity of light that they need • ie-Impatiens grow better in shade with indirect light • Zinnias grow best in full sunlight

10. Light Duration • Photoperiodism is a growth response to the length of dark period • This determines if a plants is growing vegetatively or is in the flowering stage • In a greenhouse we can force a plant to bloom by controlling the duration of light

11. Flowering plants include short-day, long-day and day-neutral plants • Short-day Plants-must be exposed to light periods shorter than some critical length for flowering to occur • ie-Poinsettia • Long-day Plants-must be exposed to light periods longer than some critical length for flowering to occur • ie-Azalea

12. Long-day, Short-day and Day-nuetral • Day-neutral Plants-These plants flower regardless the day length • ie-Dandelion http://home.jtan.com/`russ/terri/trash.htm

13. Ways to influence blooming or vegetative growth • Use a black cloth to shorten days. This involves covering the plants with an opaque cover to shorten days • Artificial light stimulates long days by adding light in the evening hours

14. Other Light Effects • Phototropism is the growth response in which plants turn or bend in the direction of the light soource • Geotropism is the growth response in which plants turn or bend in response to gravity http://biosci.cbs.umn.edu/labs/koukkari/teaching/courses/Angiosperms_30May.html

15. Moisture is also essential for plant growth • Water carries essential nutrients from the roots and acts as a solvent for salts and minerals • Water translocates photosynthetic products from the leaves via the phloem • Water is a chemical reactant in may plant processes including photosynthesis and respiration

16. Moisture • Water quality is important to plants • Excessive salt can cause leaf burn, root corrosion, poor seed germination, wilting and killing • Capillary water is used by the plants • Capillary is when the water makes contact with the soil and it is elevated of depressed depending on the relative attraction of the molecules or water

17. Moisture • Capillary continued • Water moves freely in the soil and can move up or down, horizontally • ie-dip the end of a napkin into a glass of water and observe water as it moves up through the napkin http://199.212.16.18/msc/as/index_e.html

18. Moisture Not Available To Plants • Gravity water-which is lost due to drainage • Hygroscopic water that bonds to soil particles • The bonding is ionic charge related to the size of the soil particle and its electrical charge • The charge is opposite that if water and will attract or hold the water in the soil making it unavailable to plants

19. Moisture • Plants with large thin leaves lose water more readily and have high water requirements • Plants with small waxy leaves have a tendency to lose less water to transpiration and have less water requirements • Desert plants have small leaf surfaces while tropical plants have a large leaf surface

20. Carbon Dioxide is Required for Photosynthesis • Carbon Dioxide is taken in through the stomata • Air contains .03% Carbon Dioxide • Greenhouses need to have CO2 added • Roses, carnations and tomatoes need 12% • This can be accomplished by using gas burners http://csee.lbl.gov/ScienceEd/Tony/chemistry/html

21. Carbon Dioxide • Plants use 16 essential nutrients and are available in the soil • Primary nutrients-N, P, K • Secondary nutrients-Ca, S, Mg • Trace nutrients-Mn, Fe, Zn, Cu, Cl, B, Mo • C, H, O-usually not limited since they are freely available in the air and water

22. Hormones • Hormones are low molecular weight chemicals produced in the plant to regulate growth • Auxin-promotes cell elongation, apical dominance, induces roots on cuttings, stimulates fruit development and stimulates ethylene synthesis

23. Hormones • ABA-Stimulates stomatal closure, may be necessary for abscission and dormancy in some species • Cytokinin-Promotes apical dominance, shoot growth and fruit development • Giberellins-GA-Flowering stimulation in long-day plants and biennials, shoot elongation and regulates production of seed enzymes in cereals

24. Hormones • Ethylene-Promotes fruit ripening, leaf and flower senescence and abscission

25. References • Carbon Dioxide Picture: http://csee.lbl.gov/ScienceEd/Tony/chemistry/html • Dandelion Picture: http://home.jtan.com/`russ/terri/trash.htm • Rain Drop Picture: http://199.212.16.18/msc/as/index_e.html • Rainbow Picture: http://204.97.147.10/card/paper.htm • Sunflower Picture: http://biosci.cbs.umn.edu/labs/koukkari/teaching/course/Angiosperms_30May.html • Sun Picture: http://expage.com/page/waxsteel • Thermometer Picture: http://home.earthlink.net/`bob4mvg/Time_n_Temperature.htm

26. Conclusion • Moisture, Temperature, Light, Carbon Dioxide and Hormones are required in various amounts for different plants but are all requirements for a plant to grow.