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Chapter 37 Plant Nutrition 植物營養 PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Nutritional Network (營養網路) • Every organism is an open system connected to its environment by a continuous exchange of energy and materials. • In the energy flow and chemical cycling that keep an ecosystem alive, plants and other photosynthetic autotrophs perform the key step of transforming inorganic compounds into organic ones. • Plants need sunlight as the energy source for photosynthesis. And to synthesize organic matter, plants also require raw materials in the form of inorganic substances: carbon dioxide, water, and a variety of minerals present as inorganic ions in the soil. • With its ramifying root system and shoot system, a plant is extensively networked with its environment----the soil and air, which are the reservoirs of the plants inorganic nutrients. • For a typical plant water and minerals come from the soil, while carbon dioxide (CO2) comes from the air Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Key Concepts • Concept 37.1: Plants require certain chemical elements to complete their life cycle • Concept 37.2: Soil quality is a major determinant of plant distribution and growth • Concept 37.3: Nitrogen (N) is often the mineral that has the greatest effect on plant growth • Concept 37.4: Plant nutritional adaptations (營 養適應) often involve relationships with other organisms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The branching root system and shoot system of a vascular plant – Ensure extensive networking with both reservoirs of inorganic nutrients (無機營養) Root and shoot systems of a pea seedling Figure 37.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 37.1: Plants require certain chemical elements to complete their life cycle • Plants derive most of their organic mass from the CO2 of air, but they also depend on soil nutrients such as water and minerals • Mineral nutrients CO2, the source of carbon for photosynthesis, diffuses into leaves from the air through stomata. CO2 Minerals Roots absorb H2O and minerals from the soil. H2 O O2 Through stomata, leaves expel H2O and O2. O2 CO2 H2O Roots take in O2 and expel CO2. The plant uses O2 for cellular respiration but is a net O2 producer. Figure 37.2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Functions of water in plants • Solvent in the cell • Photosynthetic reactant • Metabolic reactant or product • Respiration • Vacuolar content for cell elongation and extension • Turgor pressure • Others Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Macronutrients and Micronutrients 巨量營養素與微量營養素 • More than 50 chemical elements – Have been identified among the inorganic substances in plants, but not all of these are essential (必需的/必要的) • Essential elements (必需元素) – A chemical element is considered essential If it is required for a plant to complete a life cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydroponic culture and essential elements(水耕 法與必需元素) • Researchers use hydroponic culture (水耕法) to determine which chemicals elements are essential APPLICATION In hydroponic culture, plants are grown in mineral solutions without soil. One use of hydroponic culture is to identify essential elements in plants. TECHNIQUE Plant roots are bathed in aerated solutions of known mineral composition. Aerating the water provides the roots with oxygen for cellular respiration. A particular mineral, such as potassium, can be omitted to test whether it is essential. Control: Solution containing all minerals Experimental: Solution without potassium (K+) RESULTS If the omitted mineral is essential, mineral deficiency symptoms occur, such as stunted growth and discolored leaves. Deficiencies of different elements may have different symptoms, which can aid in diagnosing mineral deficiencies in soil. Figure 37.3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 17 essential elements=9 macro- and 8 micrnutrients • Nine of the essential elements are called macronutrients (巨量營養素), because plants require them in relatively large amounts – C, O, H, N, S, P, K, Ca • The remaining eight essential elements are known as micronutrients (微量營養素) – Because plants need them in very small amounts – Cl, Fe, B, Mn, Zn, Cu, Mo, Ni Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Essential elements in plants Table 37.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symptoms of Mineral Deficiency (礦物質缺乏的症狀) • The symptoms of mineral deficiency – Depend partly on the nutrient’s function – Depend on the mobility of a nutrient within the plant – Chlorosis (黃化現象) • Deficiency of a mobile nutrient (移動力強的元素) – Mg – Usually affects older organs more than young ones – Drawing power (汲取力) is stronger in young organs • Deficiency of a less mobile nutrient (移動力弱的元素) – Fe – Usually affects younger organs more than older ones Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The most common deficiencies – Are those of nitrogen (N), potassium (K), and phosphorus (P) Healthy/normal 磷缺乏 Phosphate-deficient 鉀缺乏 Potassium-deficient 氮缺乏 Nitrogen-deficient Figure 37.4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 報告完畢 敬請指教 !? !? !? !? !? !? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 37.2: Soil quality (土壤質地) is a major determinant of plant distribution and growth • Along with climate (氣候) – The major factors determining whether particular plants can grow well in a certain location are the texture and composition of the soil (土壤質地與組成) • Texture (質地) – Is the soil’s general structure • Composition (組成) – Refers to the soil’s organic and inorganic chemical components Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Texture and Composition of Soils(土壤質地與組成) • Various sizes of particles derived from the breakdown of rock (岩石) are found in soil – Along with organic material (humus腐植質) in various stages of decomposition (分解) • The eventual result of this activity is topsoil (頂 層土壤) – A mixture of particles of rock and organic material Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The topsoil (表土/頂層土壤) and other distinct soil layers or horizons (土壤分層) – Are often visible in vertical profile (垂直剖面/斷面) where there is a road cut or deep hole A The A horizon is the topsoil, a mixture of broken-down rock of various textures, living organisms, and decaying organic matter. B C The B horizon contains much less organic matter than the A horizon and is less weathered (風化程度). The C horizon, composed mainly of partially broken-down rock, serves as the “parent” material for the upper layers of soil. Figure 37.5. Soil layers or horizons (土壤分層) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The availability (可利用性) of soil water and minerals • After a heavy rainfall, water drains away from the larger spaces of soil. But smaller spaces retain water because of its attraction to surfaces of clay and other particles • The film of loosely bound water is usually available to plants (與土壤結合不緊密的薄水層的水才能被根吸收) 親水性 Soil particle surrounded 土壤粒子 by film of water (a) Soil water. A plant cannot extract all the water in the soil because some of it is tightly held by hydrophilic soil particles. Water bound less tightly to soil particles can be absorbed by the root. 土壤結合不緊密 親水性土壤粒子 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Root hair Water available to plant 土壤結合 不緊密 Air space Figure 37.6a Cation exchange in oil (土壤中的陽離子交換) • Acids (???) derived from roots contribute to a plant’s uptake of minerals when H+ displaces (排擠 /取代) mineral cations from clay particles (粘土粒 子) 土壤粒子表面帶負電 Soil particle K – + –– – Cu2+ K+ – – Mg2+ – K + – – Ca2+ H+ H2O + CO2 2 H2CO3 HCO3– Root hair + H+ 1 (b) Cation exchange in soil. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by (1) secreting it from root hairs and also by (2) cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid (H2CO3). Dissociation of this acid adds H+ to the soil solution. Figure 37.6b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Soil Conservation and Sustainable Agriculture 土壤保育與永續(可持續)農業 • In contrast to natural ecosystems (自然生態系 統) – Agriculture (1) depletes the mineral content of the soil, (2) taxes water reserves, and (3) encourages erosion • The goal of soil conservation strategies (土壤保 育策略的目標) – Is to minimize this damage Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fertilizers (肥料) • Commercially produced fertilizers – Contain minerals that are either mined or prepared by industrial processes • “Organic” fertilizers (有機肥料) – Are composed of manure (糞便), fishmeal (魚 肉), or compost (堆肥) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Deficiency warnings from “smart” plants • Agricultural researchers are developing ways to maintain crop yields while reducing fertilizer use • Genetically engineered “smart” plants (遺傳工程智 慧植物) inform the grower when a nutrient deficiency is imminent (急迫性營養缺失) No phosphorus deficiency Figure 37.7 Beginning phosphorus deficiency Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Well-developed phosphorus deficiency Irrigation (灌溉) • Irrigation, which is a huge drain on water resources when used for farming in arid regions (乾旱地區) – Can change the chemical makeup of soil • Topsoil from thousands of acres of farmland – Is lost to water and wind erosion (水與風的侵 蝕) each year in the United States Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 等高線耕地 • Certain precautions (預警) – Can prevent the loss of topsoil Figure 37.8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The goal of soil management (土壤管理的目標) – Is sustainable agriculture (永續農業), a commitment embracing (using) a variety of farming methods that are conservation-minded (保育理念) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Soil Reclamation (土壤復育) • Some areas are unfit for agriculture – Because of contamination of soil or groundwater with toxic pollutants • A new method known as phytoremediation (植 物復育) – Is a biological, nondestructive (非破壞性) technology that seeks to reclaim contaminated areas – A part of bioremediation (生物復育) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 報告完畢 敬請指教 !? !? !? !? !? !? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings •Concept 37.3: Nitrogen is often the mineral that has the greatest effect on plant growth •Plants require nitrogen (N) as a component of – Proteins – nucleic acids – chlorophyll – other organic molecules G A Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings C T U Soil Bacteria and Nitrogen Availability (氮的利用) • Nitrogen-fixing bacteria (固氮細菌) convert atmospheric N2 to nitrogenous minerals that plants can absorb as a nitrogen source for organic synthesis • N2+8e-+8H++16ATP Atmosphere nitrogenase Atmosphere N2 1.固氮細菌 N2 2NH3+H2+16ADP+16Pi Soil N2 4.脫氮細菌 Nitrogen-fixing bacteria Denitrifying bacteria H+ Soil (From soil) 銨鹽 NH 氨 3 離子 (ammonia) + NH4 (ammonium) Nitrifying bacteria Organic material (humus) 有機物質(腐質土) Ammonifying bacteria 2.氨化細菌 3.硝化細菌 Nitrate and nitrogenous organic compounds exported in xylem to shoot system NH4+ NO3– (nitrate) 硝酸鹽 離子 Root Figure 37.9. The role of soil bacteria in the nitrogen nutrition of plants. 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 (營養不良): protein deficiency Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 報告完畢 敬請指教 !? !? !? !? !? !? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 37.4: Plant nutritional adaptations often involve relationships with other organisms 植物營養適應通常包括其與其它微生物的關係 • Two types of relationships plants have with other organisms are mutualistic (相互的) – Symbiotic nitrogen fixation (共生的固氮作用) – Mycorrhizae (菌根) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Role of Bacteria in Symbiotic Nitrogen Fixation (共生固氮作用細菌的角色) • Symbiotic relationships with nitrogen-fixing bacteria (固氮細菌) by coevolution (共同演化) – Provide some plant species with a built-in source of fixed nitrogen • From an agricultural standpoint – The most important and efficient symbioses (共 生) between plants and nitrogen-fixing bacteria occur in the legume family (peas, beans, and other similar plants) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Along a legumes possessive roots are swellings (膨脹物/隆起物) called nodules (根瘤), plant cells – Composed of plant cells that have been “infected” by nitrogen-fixing Rhizobium bacteria Nodules 根瘤 Roots (a) Pea plant root. The bumps (腫塊) on this pea plant root are nodules containing Rhizobium bacteria. The bacteria fix nitrogen and obtain photosynthetic products supplied by the plant. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 37.10a • Inside the nodule (根瘤), which a plant cell – Rhizobium bacteria assume a form called bacteroids (類菌體), which are contained within vesicles (囊泡) 5 m formed by the root cell Infected root cell of nodule Bacteroids within vesicle 囊泡中的 類菌體 vesicle Uninfected cell of root 大豆根瘤中的類菌體 (b) Bacteroids in a soybean root nodule. In this TEM, a cell from a root nodule of soybean is filled with bacteroids in vesicles. The cells on the left are uninfected. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 37.10b • The bacteria of a nodule (根瘤中的細菌) – Obtain sugar from the plant and supply the plant with fixed nitrogen • Each legume (豆科) – Is associated with a particular strain (菌株) of Rhizobium Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Development of a soybean root nodule (大豆根瘤的發育) (1) Roots emit chemical signals that attract Rhizobium bacteria. The bacteria then emit signals that stimulate root hairs to elongate and to form an infection thread by an invagination of the plasma membrane. 根瘤菌 Rhizobium bacteria Infection thread 感染絲 類菌體 Bacteroid Infected root hair (2) The bacteria penetrate the cortex within the Infection thread. Cells of the cortex and pericycle begin dividing, Dividing cells and vesicles containing the in pericycle bacteria bud into cortical 2. cells from the branching infection thread. This process results in the formation of bacteroids Dividing cells in root cortex 1 2 Developing root nodule 3 (4) The nodule develops 4 vascular tissue that supplies nutrients to the nodule and carries nitrogenous compounds into the vascular cylinder for distribution throughout the plant. Figure 37.11 發育中 的根瘤 Bacteroid 類菌體 4 類菌體 Bacteroid Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nodule vascular tissue 根瘤的 維管組織 (3) Growth continues in 3 the affected regions of the cortex and pericycle, and these two masses of dividing cells fuse (融合), forming the nodule. The Molecular Biology of Root Nodule Formation • The development of a nitrogen-fixing root nodule depends on chemical dialogue (化學對話) between Rhizobium bacteria and root cells of their specific plant hosts Activation of Nod box by activated Nod D Expression of Nod gene Synthesis of Nod factor Activation of factor Nod D by flavonoid Chemical Signal between root and Rhizobium Flavonoid released by root as signal Nod factor trigger development by the root of the infection thread and nodule Activation of early nodule genes, leading to formation of infection thread and proliferation of cortical cells 此圖見第六版 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic Nitrogen Fixation and Agriculture 共生的固氮作用與農業 • The agriculture benefits of symbiotic nitrogen fixation – Underlie crop rotation (作物輪作/輪耕) • In this practice – A non-legume such as maize is planted one year, and the following year a legume is planted to restore the concentration of nitrogen in the soil (恢復土壤氮濃度) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae and Plant Nutrition (菌根與植物營養) • Mycorrhizae (菌根), may be an evolutionary adaptation – Are modified roots (變形根) consisting of mutualistic (相互的) associations of fungi and roots • The fungus (真菌) – Benefits from a steady supply of sugar donated by the host plant (寄主植物穩定地供給糖類給真菌) • In return, the fungus – Increases the surface area of water uptake and mineral absorption and supplies water and minerals to the host plant (真菌回報以增加寄主植物根的表面績, 以增加水份與礦物質的吸收) – Produce growth factor and antibiotics for host plants Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Two Main Types of Mycorrhizae (菌根) • In ectomycorrhizae (外根菌), no formation of root hair – The mycelium (菌絲體) of the fungus forms a dense sheath (濃密的鞘) over the surface of the root 表皮 皮層 Epidermis Cortex Mantle (fungal sheath) 外套膜 100 m Endodermis 內皮 a Mantle (fungal sheath) 外套膜 Fungal hyphae between cortical cells (colorized SEM) (a) Ectomycorrhizae. The mantle of the fungal mycelium ensheathes the root. Fungal hyphae extend from the mantle into the soil, absorbing water and minerals, especially phosphate. Hyphae also extend into the extracellular spaces of the root cortex, providing extensive surface area for nutrient exchange between the fungus and its host plant. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 37.12a The Two Main Types of Mycorrhizae (菌根) • In endomycorrhizae (內根菌), formation of root hair – Microscopic fungal hyphae extend into the root 表皮 Epidermis 皮層 Cortex Cortical cells 10 m 內皮 2 Fungal hyphae 菌絲 Root hair Endodermis Vesicle Casparian strip Arbuscules 枝狀瘤 (LM, stained specimen) (b) Endomycorrhizae. No mantle forms around the root, but microscopic fungal hyphae extend into the root. Within the root cortex, the fungus makes extensive contact with the plant through branching of hyphae that form arbuscules, providing an enormous surface area for nutrient swapping. The hyphae penetrate the cell walls, but not the plasma membranes, of cells within the cortex. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 37.12b Agricultural Importance of Mycorrhizae (菌根在農業上的重要性) • Farmers and foresters – Often inoculate (接種) seeds with spores of mycorrhizal fungi to promote the formation of mycorrhizae • Green manure and crop rotation (綠肥與輪作) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Epiphytes, Parasitic Plants, and Carnivorous Plants • Some plants have nutritional adaptations (營養適 應) that use other organisms in nonmutualistic ways (非互利共生) – Epiphytes (附生植物) – Parasitic Plants (寄生植物) – Carnivorous Plants (食蟲植物) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exploring unusual nutritional adaptations in plants EPIPHYTES Staghorn fern, an epiphyte PARASITIC PLANTS Host’s phloem Dodder Haustoria Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite (菟絲子) Indian pipe, a Nonphotosynthetic parasite (水晶蘭) CARNIVOROUS PLANTS Venus’ flytrap Pitcher plants Figure 37.13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sundews 報告完畢 敬請指教 !? !? !? !? !? !? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Molecular Biology of Root Nodule Formation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings