IGCSE Biology Paper-3: Specimen Questions with Answers 309 - 310 of 358
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Question 309
Write in Short
Short Answer▾Leaves contain two types of transport tissue, xylem, and phloem.
State which substances are transported by: xylem …
phloem …
Explanation
Vascular Bundles
Vascular bundles are conjoint, collateral, and closed type. Xylem is end arch.
Xylem is towards adaxial or upper surface and phloem towards abaxial surface. Each vascular bundle is surrounded by a sheath of parenchymatous cells called bundle sheath. Vascular bundle of midrib is the largest and parenchyma is spread from bundle sheath on both sides up to epidermis.
Xylem transports water and minerals and in turn phloem transports products of photosynthesis.
Question 310
Write in Short
Short Answer▾(i) Name the green substance that plants need for photosynthesis.
(ii) Name the gas that plants need for photosynthesis.
(iii) Name the gas that plants produce during photosynthesis.
Explanation
- The green pigment, chlorophyll, required for photosynthesis is not diffused throughout the cell. Instead, it is localized in chloroplasts. In cyanobacteria and other bacteria, which do not have chloroplasts, pigments are located on the thylakoids.
- For photosynthesis green plants take carbon dioxide from the air. The carbon dioxide enters the leaves of the plant through the stomata present on their surface. Each stomatal pore is surrounded by a pair of guard cells.
- Plants need to excrete excess carbon dioxide and oxygen. Carbon dioxide is a waste product of aerobic respiration in plant cells. Oxygen is a waste product of photosynthesis.
