Chapter 37 Plant Nutrition 09 08 2015 Phosphate potassium nitrogen are the most important elements for plants NPK Different plants need different levels of each Table 37 1 Ions are cofactors for chemical reactions A lot of elements come into plants as ions Plants need iron in cytochromes Every chlorophyll has magnesium Nutrients come in as ions for the most part Cation exchange Plant root sends out hydrogen and carbon dioxide releases positive ions from soil particles and goes into roots Mutualism symbiotic relationship between bacteria and plants figure 37 10 Plants can t use atmospheric nitrogen o Then can use nitrate or ammonium Nitrogen fixing bacteria o Takes nitrogen from the air and turns it into ammonia Ammonifying bacteria o Breaks down takes in organic material to make ammonia Hydrogen ions from soil turn ammonia ammonium Nitrifying bacteria o Changes ammonium into nitrate and moves it into the xylem Some plants have nodules on their roots Spaces for the nitrogen fixing bacteria to live Bacteroid the bacteria that lives inside the plants roots Root nodule formation 1 root sends out flavonoid only goes to good bacteria 2 flavonoid moves in bacteria and hooks up with Nod D transcription factor 3 Nod D connects to a Nod box turns on genes 4 nod genes make nod factor 5 Nod factor moves out of the bacteria 6 Nod factor moves into the roots leading to the formation of infection thread and proliferation of cortical cells infects root hairs Figure 37 12 1 Chemical signals attract bacteria 2 Bacteroid forms 3 Growth continues and root nodule forms 4 Nodule develops vascular tissue 5 Mature nodule grows to be many times the diameter of the root leghemoglobin binds oxygen to keep the oxygen from getting to high levels so the nitrogenase enzyme won t be inhibited feeds the oxygen into cellular respiration fungus is one of the worst thing for plants can break down wood eats away xylem vascular system mycorrhizae fungus root good fungi stays mostly on the outside of roots increases surface area for the plant root more water intake helps the plant get phosphate fungus secretes growth hormones keeps unwanted bacteria from coming in antibiotics plant provides sugar to the fungus epiphyte plants that live growing onto another tree use it solely for support ie orchids Spanish moss mistletoe a photosynthetic parasite can photosynthesize but lives off of other plants instead dodder can t photosynthesize true parasite orange color Indian pipe parasitize the roots of other plants Carnivorous insectivorous plants Live in nitrogen poor soil Pitcher plants Tall with modified leaves Nectaries pitchers that produced a nectar that attracts insects downward pointing hairs that make it near impossible to climb out pool of water at the bottom to drown the insect which is then dissolved by the plant Venus flytrap Smell that attracts inset inside Digests the insect to draw out nitrogen Sundews Traps insect in hair with dewlike sticky material Bladderwort wort herb Floats on water Bladder sucks in insect from the water then digests nitrogen 09 08 2015 09 08 2015