Plant Nutrition

Plant Function Video 39.3 Pollination of a Chs 38, 39 (parts), 40 night-blooming cactus by a bat

KEB no office hour on Monday 23 March 10 March 2009 Videos: ECOL 182R UofA 39.3, 34.3, 39.1, 34.1 Web Browser Open K. E. Bonine 1 2

How do plants get nutrients they need? Plant Usually from soil through roots. A few interesting Nutrition exceptions…

182 Bonine http://www.youtube.com/watc h?v=ymnLpQNyI6g&feature=r Spring 2009 elated 10 March (Freeman Ch38) 3 4

. In addition to carbon dioxide and water, Nutritional Requirements plants require essential nutrients. • early 1600s, classic experiment by van . Most nutrients are available as ions Helmont dissolved in soil water and are taken up by roots. • mass of a growing plant comes from soil? • mass of a growing plant comes from . Nutrient absorption occurs via water? specialized proteins in plasma membranes of root cells. Most plants also obtain nitrogen or phosphorus from • [Most of the mass of the tree actually fungi associated with their roots. comes from carbon dioxide in the 5 atmosphere] 6

1 Which Nutrients Are Essential?

• An essential nutrient: required for both normal growth and reproduction and for a specific structure or metabolic function.

• There are 17 essential nutrients for most vascular plants.

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Which Nutrients Are Essential? • Macronutrients are the building • Classified based on whether from water blocks of nucleic acids, proteins, &/or carbon dioxide versus from soil. carbohydrates, phospholipids, and other key molecules required in relatively large quantities. They are • Essential nutrients available from H2O •nitrogen (N) or CO2 are oxygen (O), carbon (C), and hydrogen (H). They make up 96% of the • potassium (K) plant. • calcium (Ca) •magnesium (Mg) • Soil elements can be divided into • phosphorus (P) macronutrients and micronutrients. • sulfur (S). 9 10

Which Nutrients Are Which Nutrients Are Essential? Essential? • Limiting nutrients are macronutrients that commonly • Micronutrients are required in very act as limits on plant growth. small quantities. Rather than acting as components of macromolecules, •N, P,and K are often limiting they usually function as cofactors for nutrients. specific enzymes. Examples include: • iron, zinc, boron, copper, and nickel.

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2 nutritional deficiencies

• Hydroponic growth takes place in liquid cultures, without soil, so the availability of nutrients can be precisely controlled.

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Soil Soil Formation Begins with • Weathering—the forces applied by rain, running water, and wind— Erosion of Rock begins the process of building soil from solid rock.

• Particles derived from rocks are Wind Freezing Water Organisms Soil texture is categorized by particle and (rain) (plants, lichens, size: Gravel Sand thawing moss, fungi, animals, P bacteria, archaea) the first ingredient in soil. As articles P (>2.0 mm) (0.02–2.0 mm) ar organisms occupy the substrate, tic les Silt Clay they add dead cells and tissues. Pa rtic Soil formation begins when les (0.002–0.02 mm) (<0.002 mm) This organic matter is called wind, temperature changes, rain, and organisms break Solid rock P Soil articl humus. small particles off solid rock es Succession… • Organic + Inorganic = Mature Soil 17 18

3 What Factors Affect What Factors Affect Nutrient Availability? Nutrient Availability? • Cations tend to bind to soil particles, while anions stay in • Soil pH can also influence the solution. availability of essential elements. Soils can be acidic (low pH) or alkaline (high pH). • The loss of nutrients via washing is called leaching.

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Root Hairs Increase the Surface Mechanisms of Nutrient Area Available for Nutrient Absorption Uptake • Plant cell walls are permeable to ions,

Zone of small molecules, and even large maturation Root molecules. hairs • The plasma membrane, however, is highly selective. Membrane proteins allow only specific ions to cross the plasma membrane. 21 22

Ions Enter Roots along Establishing and Using a Electrochemical Gradients Created by Proton Gradient Proton Pumps • Root-hair cells have proton pumps Root hair + (H -ATPases) in their plasma Proton pumps establish an electrochemical gradient. membranes that move nutrients into

the cell against a strong Outside cell Proton (positive) concentration gradient. pump Net positive charge P! AT s Net negative charge st Inside cell Co (negative)

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4 Anions Enter Roots via Cations Enter Roots via CHANNELS COTRANSPORTERS

Cations enter root hairs via Anions enter root hairs via channels. cotransporters.

Proton pump Proton Cotrans- Channel pump porter

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Cation vs Anion Nutrients •Anionseasier to get than cations – But anions can leach out of sandy soils – Anions better retained in clay soils

•Cationsoften bound to organic or Cation exchange! inorganic soil particles H+ (proton) for Mg+ or K+ or Ca+ etc. •Cationexchange! –H+ (proton) for Mg+ or K+ or Ca+ etc. Plants facilitate by pumping – Plants facilitate by pumping H+ out of root hairs H+ out of root hairs

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Nutrient Transfer via mycorrhizae

Fungal Soil provide nitrogen Mycorrhizal Fungi hypha and/or • Vast majority of plants take up The hyphae secrete enzymes that digest phosphorus to macromolecules. The nutrients through their root hairs hyphae than absorb the resulting ions the plants in

Mycorrhizae exchange for • But, most need more nitrogen and provide nutrients Plants provide to plants sugar. phosphorus sugars to mycorrhizae Cross section of plant root • Help from fungi that live in close association with their roots. Symbiotic

Photosynthetic mutualism • These fungi are called mycorrhizae products 29 30

5 Not all soil ions are “good” for the plant cranberries peat In Salt-Tolerant Plants, an Antiporter Concentrates Sodium in Vacuoles

In the tonoplast, antiporters send H+ out and Na+ in.

carnivores Why are these all found Proton in the same habitat? Inside vacuole pump Antiporter -Stagnant water -Low oxygen levels Tonoplast -Acidic Proton gradient Proton -Nutrient poor ‘mummies’ = Decomposition Slow Cytoplasm 31 BOGS 32

Nitrogen Fixation Some species of plant have • Plants and other eukaryotes cannot specialized methods of obtaining use N from the atmosphere. nutrients, including associations 2 with nitrogen-fixing bacteria, • However, some bacteria are able to parasitism, and carnivory. absorb N2 from the atmosphere and convert it to ammonia, nitrates, and nitrites in a process called nitrogen fixation.

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Nitrogen Fixation In Some Plants, Roots • Such bacteria often take up residence Form Nodules where Nodule in cross section inside plant root cells. Nitrogen-Fixing Bacteria Live • For example, members of the bacterial genus Rhizobium associate with plants in Roots of the pea family (legumes). pea plant

• Rhizobia (Rhizobium species and close relatives) are found in nodules on the roots of legumes and provide the plant with • ammonia in return for sugar and Nodules protection 35 36

6 Nutritional Adaptations of Plants Epiphytic Plants •Mostplants use proton pumps as a • Epiphytes are plants that mechanism for importing nutrients are adapted to grow in from the soil and/or acquire nutrients the absence of soil. They from symbiotes. often grow on leaves or •In addition, 99% of plants make their branches of trees. own sugars. • They absorb most of the • Some plants don’t follow these water and nutrients they rules, some appear to live on: need from rainwater, dust, and particles that •1)air?, some 2) parasitize others, collect in their tissues or

some catch 3) insects. 37 in the crevices of bark. 38

Epiphytes Are Adapted to Grow Parasitic Plants

in the Absence of Soil • Most parasitic plants make their own Epiphytes grow on trees (e.g., Bromeliads). sugars through photosynthesis and tap into the vascular tissue of their hosts for water and essential nutrients.

• Some plant parasites are nonphotosynthetic and obtain all their nutrition from the host. Epiphytes

• There are at least 3000 species of

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Some Plant Parasites Tap into the Xylem Tissue of Their Hosts

Mistletoe haustoria penetrate host xylem and extract water and ions

Host xylem Mistletoe

Host tree

Mistletoe 41 42

7 Carnivorous Plants Sundews Have Modified Leaves with a Sticky Surface That Catches • Carnivorous plants use modified Insects leaves to trap insects and other animals, kill them, and absorb the prey’s nutrients.

• Carnivorous species make their own carbohydrates via photosynthesis but use carnivory to supplement the nitrogen available in the environment,

which is often lacking. 43 44

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