Plant Nutrition and Transport Chapter 26

Where do plants get nutrients? A plant needs sixteen elements to survive and grow Macronutrients: ________________________________ _____________________________________________ Micronutrients: _________________________________ _____________________________________________

Properties of Soil C, O, and H atoms are abundantly available in __________________ and _________________ Plants get the other elements they need when their roots take up ______________________________________ Soil consists mainly of mineral particles: Clay particles: attracts positively charged mineral ions in soil water Sand and silt: intervene between tiny particles of clay; allows roots to access oxygen

Properties of Soil Soils with the best oxygen and water penetration are ________________ Have roughly equal proportions of sand, silt, and clay Most plants do best in loams that contain between 10 and 20 percent __________________ Decomposing organic material (e.g., fallen leaves, feces) that releases nutrients and traps minerals Traps _________________________________in soil water

How Soils Change Soils develop over thousands of years Most form in layers, or horizons, that are distinct in color and other properties _____________: uppermost soil layer; most organic matter and nutrients for plant growth Grasslands typically have a deep layer of topsoil; tropical forests do not. Why?

How Soils Change Minerals, salts, and other molecules dissolve in water as it filters through soil Leaching: ________________ ________________________ ________________________ Soil erosion: ______________ ________________________ ________________________ Erosion

Water and Nutrient Absorption through roots Water moves from soil, through a root’s ______________and cortex, to the _________________ Osmosis drives this movement; fluid in the plant typically contains more solutes than soil water Xylem distributes water and mineral ions to the rest of the plant

Apoplastic route Cell walls are permeable to ____________and ____________. Tightly packed cells form pathway between ____________and __________________________ Soil water diffuse from epidermis→through __________→to ____________________ Cannot enter cylinder: endodermis forms ________________ Waxy, waterproof band between endodermal cells. Water enters ______________of endodermal cell. Diffuses through _________________until it enters the xylem.

Symplastic route Minerals enter cytoplasm through __________________ (transport proteins) Diffuse from cell to cell through ________________until it reaches the xylem

Pathways of water absorption

Mutualisms Mycorrhiza Mutually beneficial interaction between a ______and a _______ Filaments of the fungus (hyphae) form a velvety cloak around roots or penetrate their cells Root cells get some scarce minerals that the fungus is better able to absorb nitrogen-fixing Rhizobium Roots release certain compounds recognized by compatible Rhizobium Roots encapsulate Rhizobium bacteria inside swellings called ______________________ Rhizobium in root nodules fix ____________to ammonia for plant use Plant provides oxygen-free environment and sugars to the anaerobic Rhizobium bacteria

Transport in Xylem Water that enters a root travels to the rest of the plant inside tubes of ________________ _____________cells deposit secondary wall material Just before the cells die, they digest away most of their ______________ Holes/pits remain in secondary walls where ____________________once connected living cells In mature _______ tubes, water flows laterally through the pits, between adjacent cells

Xylem structure Cell types: _____________: Tapered cells of xylem that die when mature Their interconnected, pitted walls remain and form water- conducting tubes _____________________: Cells that form in stacks in xylem and die when mature Their pitted walls remain to form water-conducting tubes Each tube consists of a stack of ____________that meet end to end at perforation plate

Cohesion-Tension Theory Tracheids and vessel elements that compose xylem tubes are ____and cannot pump water upward against ___________ The movement of water in vascular plants is driven by two features of water: _______________________________

Cohesion-Tension Theory Cohesion–tension theory: water in xylem is pulled upward by air’s drying power, which creates a continuous negative pressure called _______________ Transpiration: __________________________________ _____________________________________________ Creates tension that pulls a cohesive column of water upward through xylem Water resists breaking into droplets. Why? ______________________

Conserving water (Land plants) In land plants, at least 90 percent of water taken up by roots is lost by ___________________ A waterproof _________ helps a land plant conserve water The cuticle also restricts __________________with air

Conserving water (Land plants) Stoma: ______________________________________ (specialized cells of epidermis) When guard cells swell with water, they bend slightly forming a gap (the __________) Open stomata allow gases and water vapor to cross the ________________ When guard cells lose water, they collapse against one another, __________________ guard cells closed stoma open stoma

Conserving water (Land plants) Stomata open or close based on environmental cues Example: light from the sun causes guard cells to begin pumping potassium ions Water follows the ions by osmosis, plumping the guard cells, ______________________________ Carbon dioxide diffuses through the open stomata into the plant’s tissues, and ____________________begins

Phloem structure Sieve tubes: sugar- conducting tube of phloem; consists of stacked sieve elements Sieve elements are living cells that meet end to end at sieve plates ___________________: parenchyma cells that provide metabolic support to its partnered ____________________

Pressure flow theory Sugars are transported via ___________________ Movement of sugars through phloem is called ___________ Inside sieve tubes, fluid rich in sugars flow from a _____ to a ________because of a pressure gradient Source: _________________________________________ (photosynthetic tissues) Sink: ___________________________________________ (developing shoots and fruit) Pressure flow theory: A difference in _____(rigidity) between sieve elements in source and sink regions pushes sugar-rich fluid through a sieve tube

Pressure flow theory 1. ________gradient moves sugar-rich fluid from photosynthesizing mesophyll cells→adjacent companion cells through _____________(sometimes also active transport across membranes)→associated _____________________

Pressure flow theory 2. Sugar loading increases ______________________– hypertonic (higher osmotic pressure). Water follows the sugar by ___________, moving into ____________________.

Pressure flow theory 3. High ________________ pushes the sugar-rich cytoplasm from one sieve element to the next, towards a ________region where _______________is lower.

Pressure flow theory 4. Pressure inside sieve tube ____________at ________: Sugars leave the tube→into companion cells→diffuse into sink cells through ___________________ Water follows by _______________

Application J-Field, Aberdeen Proving Ground: From World War I until the 1970s, the United States Army tested and disposed of weapons at this site Chemicals, chemical weapons, explosives, plastics, and solvents were burned in pits Lead, arsenic, mercury, and trichloroethylene contaminated the soil and groundwater To clean up the soil and protect nearby Chesapeake Bay, the Army and the Environmental Protection Agency turned to phytoremediation The use of plants to take up and concentrate or degrade environmental contaminants