FBISE Class 9th (SSC-l)
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FBISE Class 9th (SSC-l)
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.
Answer: Higher temperature increases evaporation from leaf surfaces and therefore raises the transpiration rate.
Answer: Light triggers the opening of stomata, which in turn increases transpiration.
Answer: Transpiration pull, a negative pressure, is the main force drawing water up the xylem.
Answer: The more concentrated cell sap has a lower water potential, so water moves into the root hair by osmosis.
Answer: Water uptake by osmosis is passive and does not require metabolic energy.
Answer: Sucrose is the principal sugar translocated through the phloem of most plants.
Answer: Phloem transport is bidirectional, moving food from sources to sinks in any direction needed.
Answer: Photosynthesis uses carbon dioxide and releases oxygen during daylight.
Answer: Respiration is a continuous process that takes place in every living cell of the plant.
Answer: Respiration continues at night, so plants release carbon dioxide even when stomata are mostly closed.