Photosynthesis and Respiration — Important Questions

The splinter will glow brighter or relight because oxygen supports combustion

Step 1: During photosynthesis, Hydrilla (a water plant) releases oxygen gas as a by-product. Step 2: The gas bubbles collect in the inverted test tube by displacing water. Step 3: Oxygen is a gas that supports combustion (burning). A glowing splinter relights or glows brighter in the presence of oxygen — this is the standard test for oxygen. Step 4: Therefore, when the splinter is inserted, it relights/glows brighter, confirming the gas is oxygen. Step 5: Option A is wrong — CO₂ extinguishes flames, but Hydrilla releases O₂, not CO₂. Option C is wrong — no hydrogen is produced in photosynthesi

Glucose → stored as starch in leaf → reconverted to sucrose at night → transported via phloem to other parts

Step 1: Glucose is produced rapidly during photosynthesis but cannot be transported at the same speed. Step 2: So, multiple glucose molecules join together to form insoluble starch, which is stored temporarily in the leaf. Step 3: At night, this starch is reconverted into soluble sucrose. Step 4: Sucrose is then transported in solution through the phloem (not xylem) to different parts of the plant. Step 5: In stems and fruits, sucrose may again be stored as starch. Option B is wrong — food moves through phloem, not xylem (xylem carries water). Option C is wrong — glucose becomes sucrose/starch

To serve as a control — proving that CO₂ comes only from living germinating seeds and not from bacterial activity

Step 1: Flask A has live germinating seeds; Flask B has dead (boiled) seeds with an antiseptic — this is the control setup. Step 2: Dead seeds cannot respire, so they will not produce CO₂. Step 3: The antiseptic (carbolic acid) is added to kill any bacteria on the dead seeds that might otherwise respire and produce CO₂, which would give a false positive result. Step 4: When Flask A's gas turns lime water milky (CO₂ present) but Flask B's gas does not, it confirms that the CO₂ came only from the respiration of living germinating seeds. Step 5: This is a classic use of a control experiment to is

Xylem transports water and minerals from roots to leaves for photosynthesis; phloem transports sucrose (food) from leaves to all parts of the plant

Step 1: Plants have a vascular system made of two tissues — xylem and phloem. Step 2: Xylem transports water and minerals UPWARD from the roots to the leaves. This water is one of the raw materials needed for photosynthesis. Step 3: Phloem transports the food prepared during photosynthesis (in the form of sucrose) from the leaves to all other parts of the plant — downward and in all directions. Step 4: So xylem supplies the raw material (water), and phloem distributes the final product (food). Step 5: Options A and C are wrong — xylem does not carry glucose or food. Option D is wrong — xylem d