Chapter 37 Plant Nutrition Power Point Lectures for

Chapter 37 Plant Nutrition Power. Point Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Overview: A Nutritional Network • Every organism continually exchanges energy & materials with its environment • For a typical plant, water & minerals come from the soil, while CO 2 comes from the air • The root and shoot systems of a vascular plant ensure extensive networking with both reservoirs of inorganic nutrients Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

37. 1: Plants require certain chemical elements to complete their life cycle • Plants derive most of their organic mass from the CO 2 of air, but they also depend on soil nutrients such as water and minerals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -2 H 2 O CO 2 O 2 Minerals CO 2 H 2 O

Macronutrients and Micronutrients • > 50 chem elements r inorganic substances in plants, but not all of these are essential to plants • chem element is essential if it is req’d for a plant to complete its life cycle • Researchers use hydroponic culture to determine which chemicals elements are essential • *plants are grown in mineral soln’s w/o soil & roots are bathed in aerated solns to provide O 2 for respiration. A mineral such as K can be omitted to see if it’s essential Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -3 Control: Solution containing all minerals Experimental: Solution without potassium

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• 9 essential elements r macronutrients b/c plants require them in lg amts • 8 are micronutrients b/c plants only need small amts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Symptoms of Mineral Deficiency • Symptoms of mineral deficiency depend on the nutrient’s function & mobility w/in the plant • Deficiency of a mobile nutrient usually affects older organs > young ones (b/c young growing tissues have more “drawing” power for nutrients in short supply) • Deficiency of a less mobile nutrient usually affects younger organs > older ones (b/c older tissues will have enough of the mineral & so can retain when it’s in shor supply) • most common: N, K, & P Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Chlorosis- yellowing of leaves due to insufficient production of chlorophyll • deficiency of Mg caused yellowing of the leaves b/c it’s a part of chlorophyll • **iron deficiency also causes yellowing even though it is not in chlorophyll but it’s req’d as a cofactor in one of the enzymatic steps of chlorophyll synthesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -4 Healthy Phosphate-deficient Potassium-deficient Nitrogen-deficient

37. 2: Soil quality is a major determinant of plant distribution and growth • Climate, soil texture & composition- major factors determining whether a plant can grow well in a location • Texture- soil’s general structure • Composition- soil’s organic & inorganic chemical components • **usually mineral deficiencies are distinctive enough so that farmers can tell by looking or by checking the mineral content of the soil Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Texture and Composition of Soils • Topsoil- mix of rock particles, living organisms, & humus (the remains of partially decayed organic material) • The topsoil and other distinct soil layers, or horizons, are often visible in vertical profile where there is a road cut or deep hole • ** most fertile soils are loams + humus (= amts of sand, silt, & clay) • * they have enough fine particles to provide a lg surface area to retain water & minerals & enough coarse particles to provide air spaces Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -5 A B C

• After a heavy rainfall, water drains from the larger spaces of soil, but smaller spaces retain water because of its attraction to clay and other particles • The film of loosely bound water is usually available to plants Animation: How Plants Obtain Minerals from Soil Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -6 Soil particle surrounded by film of water Root hair Soil particle Water available to plant Root hair Air space Soil water Cation exchange in soil

• Acids derived from roots contribute to a plant’s uptake of minerals when H+ displaces mineral cations (+) from clay particles Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Soil Conservation and Sustainable Agriculture • In contrast w/ natural ecosystems, agriculture depletes the mineral content of soil, taxes water reserves, & encourages erosion • The goal of soil conservation strategies is to minimize this damage Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Fertilizers • Commercial fertilizers- minerals mined or prepped by industrial processes • Organic fertilizers- manure, fishmeal, or compost Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Agricultural researchers are developing ways to maintain crop yields while reducing fertilizer use • Genetically engineered “smart” plants inform the grower when a nutrient deficiency is imminent Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -7 No phosphorus deficiency Beginning phosphorus deficiency Well-developed phosphorus deficiency

Irrigation • Irrigation is a huge drain on water resources when used for farming in arid regions • It can change the chemical makeup of soil Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Erosion • Topsoil from 1000 s of acres of farmland is lost to water & wind erosion each year in the USA • Contour tillage- prevents topsoil loss Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The goal of soil management is sustainable agriculture, a commitment embracing a variety of farming methods that are conservation-minded Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Soil Reclamation • Some areas are unfit for agriculture because of contamination of soil or groundwater with toxic pollutants • Phytoremediation- biological, nondestructive technology that reclaims contaminated areas using plants • Bioremediation- using bacteria or protists to clean polluted sites Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

37. 3: Nitrogen is often the mineral that has the greatest effect on plant growth • Plants require N as a component of proteins, nucleic acids, chlorophyll, & other impt organic molecules Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Soil Bacteria and Nitrogen Availability • N-fixing bacteria convert atmospheric N 2 to nitrogenous minerals that plants can absorb as a N source for organic synthesis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Improving the Protein Yield of Crops • Agriculture research in plant breeding has resulted in new varieties of maize, wheat, and rice that are enriched in protein • Such research addresses the most widespread form of human malnutrition: protein deficiency Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

37. 4: Plant nutritional adaptations often involve relationships with other organisms • 2 types of relationships plants have w/ other organisms are mutualistic: – Symbiotic N-fixation, involving roots & bacteria – Mycorrhizae, involving roots & fungi Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The Role of Bacteria in Symbiotic Nitrogen Fixation • Symbiotic relationships with N-fixing bacteria provide some plant spp with a built-in source of fixed N • For agriculture, the key symbioses b/w plants & Nfixing bacteria occur in the legume family (peas, beans, and other similar plants) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• legume roots- swellings (nodules), plant cells “infected” by N-fixing Rhizobium bacteria Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -10 5 µm Bacteroids within vesicle Nodules Roots Pea plant root. Bacteroids in a soybean root nodule.

• Inside the root nodule, Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The Molecular Biology of Root Nodule Formation • The development of a N-fixing root nodule depends on chemical dialogue b/w Rhizobium bacteria & root cells of their specific plant hosts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Symbiotic Nitrogen Fixation and Agriculture • Crop rotation takes advantage of the agricultural benefits of symbiotic N-fixation • A non-legume such as maize is planted 1 year, & the next year a legume is planted to restore the concen of N in the soil Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Mycorrhizae and Plant Nutrition • Mycorrhizae are mutualistic associations of fungi and roots • The fungus benefits from a steady supply of sugar from the host plant • The host plant benefits because the fungus increases the surface area for water uptake and mineral absorption Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

The Two Main Types of Mycorrhizae • Ectomycorrhizae-mycelium of the fungus forms a dense sheath over the surface of the root Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -12 a Epidermis Cortex Mantle (fungal sheath) 100 µm Endodermis Fungal hyphae between cortical cells Mantle (fungal sheath) Ectomycorrhizae. (colorized SEM)

• Endomycorrhizae-microscopic fungal hyphae extend into the root Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -12 b Epidermis Cortex Cortical cells 10 µm Endodermis Fungal hyphae Vesicle Casparian strip Root hair Arbuscules (LM, stained specimen) Endomycorrhizae.

Agricultural Importance of Mycorrhizae • Farmers & foresters often inoculate seeds w/ fungal spores to promote formation of mycorrhizae Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Epiphytes, Parasitic Plants, and Carnivorous Plants • nutritional adaptations that use other organisms in nonmutualistic ways • Epiphytes • Parasitic plants • Carnivorous plants- acid bogs w/soil poor in N & minerals Video: Sun Dew Trapping Prey Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 37 -13 a Staghorn fern, and epiphyte. This tropical fern (genus Platycerium) grows on large rocks, cliffs, and trees. It has two types of fronds: branched fronds resembling antlers and circular fronds that form a collar around the base of the fern.

LE 37 -13 b Host’s phloem Dodder Haustoria Mistletoe, a photosynthetic parasite. Dodder, a nonphotosynthetic parasite. Indian pipe, a nonphotosynthetic parasite.

LE 37 -13 c Venus’ flytrap. Pitcher plants. Sundews.