Plant Nutrition and transport Chapter 32

Example essay question Draw a GENERAL diagram that describes how a plant undergoes alternation of generations. In your diagram include all the different phases that the plants go through and the processes that lead from one phase to another. Indicate which phases have the full chromosome number, and which have half the chromosome number.

Objectives Identify the needs of plants and the entry points of materials Fig 32.1A

Uptake and transport of plant nutrients Co2 enters plants through the leaves Water, minerals and some O2 enter through from the soil through the roots All other materials are produced through mixtures of these Energy is obtained from the respiration of sugars. Leaves produce O2 for this , roots absorb it from the soil

Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS Respiration: glucose gives up energy as it is oxidized Loss of hydrogen atoms Energy Glucose Gain of hydrogen atoms Figure 6.4

Solute uptake in the roots Fig 32.2

Solute uptake in the roots Roots have large surface area Mycorrhizal fungal interactions supply nutrients and water to the plant Substances enter roots both intracellularlly and extracellularly, control over substances occurs at the cell membrane Intracellular (root hair membrane-plasmodesmata-cortex cells, endodermal cells- xylem) Extracellular (porous cell walls,around casparian strips, to xylem

32.11 Fungi help most plants absorb nutrients from the soil Relationships with other organisms help plants obtain nutrients Many plants form mycorrhizae A network of fungal threads increases a plant's absorption of nutrients and water The fungus receives some nutrients from the plant Figure 32.11

Properties of water Water molecules stick to one Another (cohesion) and other stuff (adhesion) Water is a polar molecule Fig 2.9 Fig 2.10

Transpiration Fig 32.3

Transpiration Water – cohesion, diffusion, osmosis How do plants lift water from the roots to the leaves Root cell membranes pump solutes into the xylem, then water follows Transpiration – adhesion-cohesion Evaporation of water from leaves thru stomata Cohesion of water molecules in the xylem Adhesion of water to cellulose

Transpiration is controlled by stomata Fig 32.4

Figure 32.UN05 Figure 32.UN05 Testing your knowledge, question 7

Sugar transport Fig 32.5

Sugar transport Phloem transports sugars Sugars are made at “sugar sources” Sugars travel to and are used at “sugar sinks” Osmosis is responsible for generating pressure differences that move the sugar. Proof ! –Aphids!

Sugar sink

Aphids

Nutrients and plant health Fig 32.6B Macronutrients Carbon, Oxygen,Nitrogen,Hydrogen,Sulfur, Phosphorus, Calcium,Potassium,Magnesium Microinutrients Iron, zinc, etc

Soil and plants Fig 32.8

32.12 Most plants depend on bacteria to supply nitrogen The Earth’s atmosphere consists of about 80% nitrogen. However, nitrogen deficiency is the most common nutritional problem in plants. Why is that? Plants cannot absorb nitrogen directly from the air. Instead, to be used by plants, nitrogen must be converted to ammonium (NH4+) or nitrate (NO3–). Student Misconceptions and Concerns  Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the more general meaning of symbiosis and the win/win nature of mutualism, a type of symbiosis. Active Lecture Tips  With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to work in small groups to explain why planting seeds in sterilized soil could be problematic.

32.12 Most plants depend on bacteria to supply nitrogen Soil bacteria can convert N2 gas from the air into forms usable by plants via several processes. Nitrogen-fixing bacteria convert atmospheric N2 to ammonia (NH3) in a process called nitrogen fixation. Ammonifying bacteria add to the supply of ammonium by decomposing organic matter. Nitrifying bacteria convert ammonium to nitrates, the form most often taken up by plants. Student Misconceptions and Concerns  Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the more general meaning of symbiosis and the win/win nature of mutualism, a type of symbiosis. Active Lecture Tips  With abundant antibacterial products now on the market, students may believe that all bacteria are harmful. Before addressing the mutualistic roles of soil bacteria and plants, challenge your students to work in small groups to explain why planting seeds in sterilized soil could be problematic.

N2 ATMOSPHERE ATMOSPHERE SOIL Amino acids, etc. Nitrogen-fixing Figure 32.12-0 ATMOSPHERE N2 ATMOSPHERE SOIL Amino acids, etc. Nitrogen-fixing bacteria NH4+ H+ N2 NH3 SOIL NH4+ (ammonium) NO3− (nitrate) Nitrifying bacteria Ammonifying bacteria Figure 32.12-0 The roles of bacteria in supplying nitrogen to plants Organic material Root

32.13 EVOLUTION CONNECTION: Plants have evolved mutually beneficial symbiotic relationships Some plants form symbioses with nitrogen-fixing bacteria. Legumes (peas, beans, alfalfa, and others) form root nodules to house nitrogen-fixing symbionts in the genus Rhizobium. Other plants, such as alders, form symbioses with other kinds of nitrogen-fixing bacteria. The plant provides the bacteria with carbohydrates and other organic compounds. Student Misconceptions and Concerns  Students often confuse the terms symbiosis and mutualism, falsely thinking that they mean the same thing. You might wish to clarify these terms to emphasize the more general meaning of symbiosis and the win/win nature of mutualism, a type of symbiosis. Teaching Tips  Mycorrhizae provide an excellent example of a mutualistic relationship. Unless the various types of symbiotic relationships have already been discussed, consider illustrating mutualism and parasitism with the relationships in Modules 32.13–32.14.  For additional specific details on mycorrhizal relationships, see the literature exchange website for mycorrhiza at http://mycorrhiza.ag.utk.edu/.

Shoot Nucleus Bacteria within vesicle inside cell Nodules Roots Figure 32.13b-0 Shoot Nucleus Bacteria within vesicle inside cell Nodules Roots Figure 32.13b-0 Root nodules on a pea plant