plant species (eg legumes) with a source of fixed nitrogen f.Nitrogen fixation is the conversion of nitrogen from N2 to NH3 21. Nitrogenase enzymea.Along a legume’s roots are swellings called nodules composed of cells infected bynitrogen fixing Rhizobium bacteria i.Soybean root grows nodules 1.Plant root and nodule (lighter blue) attached to the root a.Nitrogen fixing bacteria live inside the nodule b.Inside the root nodule, Rhizobium bacteria are contained within vesicles formed by the root cell c.Bacteria attracted to root haris ,create invagination of membrane, root hair curls a littlebit, tube forms membrane to peneterate into the root, bacteria will travel through the tube (bacteria do not come into contact with root cells), in the nodule the bacteria are surrounded by vesicles i.He said not to really worry about this (infection by nitrogen fixing bacteria)d.Very important in nitrogen poor soils to have relationship e.If grow soy beans- can use less fertilizer f.In the real world – the plant is supporting bacteria in nodule – expensive! i.It is a trade off ii.If the soil is really poor in nitrogen, this is goodiii.If nitrogen in the soil , this is wasteful 1.Plant will dump the nodules if soil become suddenly fertilized withnitrogen 22. Nitrogen fixation and agriculture a.Nitrogen fixing plants grown in combo with plants that cannot do this b.Grow soy beans between rows or corn i.Leaking some nutrients, corn benefits c.OR do crop rotation i.Do beans on year, maybe plow the leaves into the ground 1.Replenishes soil ii.Do corn the next year d.Crop rotation takes advantage of the agricultural benefits of symbiotic nitrogen fixations e.A non-legume such as corn is planted one year, and the next year a legume is planted to restore the concentration of nitrogen in the soilf.EX: azolla and rice i.Where they plant rice, they often use azolla as a free fertilizer 1.Has nitrogen fixing bacteria in association with the roots – azola ii.Time to plant, drain the field of azole, plow azola into soil to dump all the nitrogen, plant and grow rice, flood field and plant azola again
PAFF Test 223. Epiphytes, parasites, and carnivorous plants a.Some plants have nutritional adaptations that use other organisms in non-mutualistic ways (above list)24. Epiphytes a.An epiphyte grows on another plant and obtains water and minerals from rain b.They are not parasites- just want to be up high in the sun, want to be in the forest/jungle c.Seedling germinating on a branch – get better access for photosynthesis d.Absorb water dripping down the trunke.Staghorn fern 25. Parasites a.Parasitic plants absorb sugars and minerals from their living host plant i.Can cause damageb.Mistletoe, photosynthetic i.Grows up high, the roots penetrate into the branch – get in under the bark and grow the sinker roots that go down into the wood – coming contact with the xylem and phloem ii.Not eating on sugar so much (do photosynthesis themselves), just get some more water iii.Doesn’t usually cause problems unless infected by like fifty of them c.