(a) (i) Name the two types of transport tissue found in the stem of a flowering plant. [2] (ii) For each tissue named in (a)(i), state the main substance it...

(a)(i) The two types of transport tissue in the stem of a flowering plant are:

1. Xylem [1]
2. Phloem [1]

(a)(ii) The main substance each tissue transports:

• Xylem transports water and dissolved mineral ions from the roots upward through the plant. [1]
• Phloem transports sugars (sucrose) and other dissolved organic solutes from sources (e.g. leaves) to sinks (e.g. roots, fruits, storage organs). [1]

(b)(i) The cassava leaves curled inward during the heat of the day because:

1. High temperature and low humidity increased the rate of transpiration significantly. [1]
2. The dry soil meant that water uptake by the roots could not keep pace with the rate of water loss from the leaves. [1]
3. As a result, the guard cells lost turgor and the stomata closed. The other leaf cells also became flaccid, causing the leaf to curl inward. This curling reduces the exposed surface area and helps limit further water loss. [1]

(b)(ii) The leaves opened out in the early morning because temperatures were lower and humidity was higher, so the rate of transpiration was much reduced. [1] With lower demand on the water supply, the roots could absorb water during the cooler period, allowing the leaf cells to regain turgor pressure and the leaves to unfurl to their normal flat shape. [1]

(c) Three methods a farmer could use to reduce water loss from crop plants (any three):

1. Apply mulch (straw, plastic, or organic matter) around the base of plants to reduce evaporation from the soil surface. [1]
2. Use drip irrigation to deliver water directly to the root zone, minimising surface evaporation and runoff. [1]
3. Plant windbreaks (rows of trees or hedges) around the field to reduce air movement over the crop, which slows the removal of the humid boundary layer from leaf surfaces. [1]

Other acceptable methods: weed regularly (weeds compete for soil moisture), irrigate during cooler parts of the day.

(d) Understanding water requirements before choosing an irrigation method is important because:

1. Different crops have different water demands at different growth stages (e.g. flowering vs. vegetative growth), so the irrigation method must be able to deliver the right volume at the right time. [1]
2. Over-irrigation wastes water and can cause waterlogging (which deprives roots of oxygen) and leaching of nutrients from the soil. [1]
3. Under-irrigation causes water stress, reduces crop yield, and may cause permanent wilting. The choice of method (drip, sprinkler, furrow) should match the crop's root depth, spacing, and water demand to ensure efficient use of the water resource. [1]