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Unit-8 Plant Physiology
Answer: Root pressure pushes water up the xylem and is a major cause of guttation.
Answer: Mineral ions are usually taken up actively, using energy, against the concentration gradient.
Answer: Respiration breaks down glucose and releases carbon dioxide, water and energy.
Answer: Diffusion is the passive movement of molecules from higher to lower concentration.
Answer: Active transport uses metabolic energy (ATP) to move substances against the concentration gradient.
Answer: The conducting cells of xylem are dead and hollow, forming continuous tubes for water flow.
Answer: Food transport is carried out by the phloem, not by transpiration.
Answer: Translocation is the movement of organic food through the phloem from source to sink.
Answer: Leaves that make food act as the source, while storage and growing parts act as sinks.
Answer: The external hypertonic solution draws water out of the cell by osmosis, causing plasmolysis.
Answer: Plants excrete gases such as carbon dioxide and oxygen along with some other waste materials.
Answer: Shedding old leaves removes the metabolic wastes that have accumulated in them.
Answer: Macronutrients such as nitrogen, phosphorus and potassium are needed in large amounts.
Answer: Chlorosis is the yellowing of leaves, often caused by a deficiency of magnesium or nitrogen.
Answer: Iron, zinc and manganese are needed only in small amounts and are therefore micronutrients.
Answer: Nitrogen deficiency results in poor growth and chlorosis because nitrogen is needed for proteins and chlorophyll.
Answer: Guard cells contain chloroplasts and change turgor to open and close the stomatal pore.
Answer: Water entering or leaving the guard cells changes their turgor, opening or closing the stomata.
Answer: Wind carries water vapour away, which increases the diffusion gradient for water loss.
Answer: High humidity reduces the diffusion gradient of water vapour, so less water evaporates.