Ch9 Nutrition and Gas Exchange in Plants PDF

🌳 Ch9 Nutrition and Gas Exchange in Plants Created @February 11, 2020 12:03 PM Volume Compulsory Tags Plant Nutrition in plants Plants as autotrophs Plants can make their own food, in form of...

🌳 Ch9 Nutrition and Gas Exchange in Plants Created @February 11, 2020 12:03 PM Volume Compulsory Tags Plant Nutrition in plants Plants as autotrophs Plants can make their own food, in form of carbohydrates from carbon dioxide and water using light energy trapped by chlorophyll through photosynthesis Oxygen is released as a by product Water required in photosynthesis is absorbed from the soil, so is minerals Since plants can synthesize organic substances from inorganic substances, they are said to be autotrophs and are called autotrophic nutrition Mineral requirements of plants Plants required a variety of minerals, absorbed in forms of ions for growth Major elements are elements needed in large amounts Trace elements are elements needed in trace amounts 1. Nitrogen Absorbed in forms of nitrate ions and ammonium ions Ch9 Nutrition and Gas Exchange in Plants 1  Required in the synthesis of proteins, as proteins are made of amino acids, which consist of nitrogen Deficiency of nitrogen leads to poor growth and yellow leaves 2. Phosphorus Absorbed in forms of phosphate ions Required in the synthesis of nucleic acids, as nucleic acids are made of nucleotides, which consist of phosphorus Required in some enzymatic reactions Deficiency of phosphorus leads to poor growth around the roots and purple patches on leaves 3. Potassium Absorbed in forms in potassium ions Promotes transport and photosynthesis in plants Required in some enzymatic reactions Deficiency of potassium leads to poor growth and cured-up leaves with dark edges 4. Magnesium Absorbed in forms of magnesium ions Required in the synthesis of chlorophyll, as chlorophyll molecules contain magnesium Deficiency of magnesium would lead to poor growth and yellow leaves Experimental set up for testing the effects of minerals on plant growth This set up is used for testing the effects of minerals (or the lack of minerals) on plant growth. The functions of each components of the set up is as follows: Ch9 Nutrition and Gas Exchange in Plants 2  1. The jar must be covered in aluminium foil to exclude light. This prevents algae from carrying out photosynthesis, thus limiting its growth. Limitation of algae growth is necessary as they may complete with the seedling for minerals, and clog up the root hair. 2. Cotton wool prevents the entry of bateria or fungi. 3. Air is bubbled in via the tube to supply oxygen for respiration by the roots (not carbon dioxide and photosynthesis). 4. There is a preference of using young seedlings than mature plants, because their rapid growth rate yields more conspicuous results. 5. Why is there a need for renewal of the nutrient solution? a. b. c. Gas exchange in plants Gas exchange in leaves Structure of a leaf Both surfaces of a leaf are covered by a layer of cells called the epidermis, which protects the inner layers of cells. Epidermal cells consist of no chloroplast, except for guard cells Both the upper and lower epidermis are covered by a thin and waxy layer called the cuticle, which reduces water loss by transpiration Below the upper epidermis is the palisade mesophyll, made of tightly-packed cylindrical cells with many chloroplast Below the palisade mesophyll is the spongy mesophyll, made of loosely-packed irregular-shaped cells with fewer chloroplast, with many air space among them The epidermis has pores called stomata where gas exchange takes place. Each stoma is guarded by two guard cells which control the opening and closing of the stoma The veins are embedded in the mesophyll, containing the vascular bundle, consisting of the xylem and phloem Ch9 Nutrition and Gas Exchange in Plants 3  Process of gas exchange in leaves Gas uptake Gases in the atmosphere diffuse through the stoma into the air space. Gases in the air space dissolve in the moist surface of the mesophyll cells and diffuses directly into the cells Gases diffuse to neighboring cells Gas release Gases produced by cells diffuse into neighboring cells towards the stoma Gases diffuse out of the cell into the moist surface of the mesophyll cells and into the air space Gases in the air space diffuse through the stoma into the atmosphere Adaptive features of leaves for gas exchange 1. Leaves are broad and flat, providing a large surface area for gas exchange to occur 2. Leaves are thin, reducing the diffusion distance of gases, facilitating gas exchange 3. The surface of the mesophyll cells are moist, allowing the gases to dissolve in it and diffuse directly into the cell, facilitating gas exchange 4. There are many air space among spongy mesophyll cells, allowing the gases to diffuse freely in the leave, facilitating gas exchange 5. Stomata are present on the epidermis, allowing gases to diffuse in and out of the cell easily, facilitating gas exchange 6. Guard cells control the opening and closing of the stoma, such that the rate of gas exchange can be regulated Ch9 Nutrition and Gas Exchange in Plants 4  Gas exchange in stems and roots Herbaceous stems have stomata for gas exchange Woody stems are covered by a layer of cork, which is impermeable to air. Gas exchange takes place in lenticels, the small broken parts of the cork Gas exchange takes place all over the roots What is the effect of light intensity on gas exchange? During the night, photosynthesis stops, only respiration occurs, there is uptake of oxygen and release of carbon dioxide At the start of the day, light intensity increases, but the rate of photosynthesis is still lower than that of respiration. Uptake of oxygen by respiration is greater than the release of oxygen by photosynthesis, release of carbon dioxide by respiration is greater than the uptake of carbon dioxide by photosynthesis. There is a net uptake of oxygen and net release of carbon dioxide At compensation point, rate of photosynthesis equals rate of respiration, there is no net gas exchange with the atmosphere As light intensity further increases, rate of photosynthesis is greater than the rate of respiration. Uptake of carbon dioxide by photosynthesis is greater than release of carbon dioxide by respiration, release of oxygen by photosynthesis is greater than uptake of oxygen by respiration. There is a net uptake of carbon dioxide and net release of oxygen. As light intensity further increases, rate of photosynthesis does not increase as the it is limited by other factors such as carbon dioxide concentration and temperature ( 🍃 Ch21 Photosynthesis), therefore, net uptake of oxygen does not increase Ch9 Nutrition and Gas Exchange in Plants 5 Ch9 Nutrition and Gas Exchange in Plants 6