(a) Maize (Zea mays) is a monoecious plant with separate male and female flowers on the same plant. (i) State the name given to the male flower cluster at t...

(a)(i) The male flower cluster at the top of a maize plant is called the tassel. [1]

(a)(ii) Pollen is released from the anthers on the tassel at the top of the maize plant. [1] Wind carries the light, dry pollen grains downward and sideways, where they land on the exposed silks (stigmas) that protrude from the ear (the female flower structure) on the same or neighbouring plants. [1]

(a)(iii) Maize is described as a cross-pollinated crop because the male flowers (tassel) and female flowers (ear/silks) on the same plant typically mature at slightly different times, a phenomenon called protandry (the tassel sheds pollen before the silks on the same plant are fully receptive). [1] This timing difference means that pollen from one plant is more likely to land on the receptive silks of a neighbouring plant rather than its own, promoting cross-pollination and genetic mixing within the population. [1]

(b)(i) Steps to produce F1 hybrid maize seed from two inbred parent lines: [5]

1. Two inbred (homozygous) parent lines, Line A and Line B, are planted in adjacent rows in an isolation plot, far enough from other maize fields to prevent contamination by stray pollen. [1]
2. Before the tassels of Line A (the designated female parent) begin to shed pollen, all tassels are physically removed from every Line A plant. This process is called detasselling. [1]
3. Because Line A plants have no tassels, they cannot self-pollinate. They can only be pollinated by wind-blown pollen from the intact tassels of neighbouring Line B plants. [1]
4. The seed that develops on the ears of Line A plants is the F1 hybrid seed, carrying one set of genes from each inbred parent. [1]
5. The F1 hybrid plants grown from this seed display hybrid vigour (heterosis), producing significantly higher yields, stronger growth and greater uniformity than either inbred parent line alone. [1]

(b)(ii) Farmers are advised to buy fresh hybrid seed each season because F1 hybrid plants are heterozygous (carrying different alleles from the two parent lines). [1] If the farmer saves grain from an F1 crop and plants it, the resulting F2 generation will segregate genetically, showing wide variation in plant height, maturity, disease resistance and yield. This genetic recombination leads to reduced vigour and uneven, lower yields compared with the uniform F1 generation. [1]

(c) Three characteristics a breeder would select for in a drought-prone region (any three): [3]

1. Early maturity / short growing season: the crop completes its life cycle before soil moisture is exhausted. [1]
2. Deep root system: roots can access water stored deeper in the soil profile during dry spells. [1]
3. Tolerance to high temperatures or water stress: the plant can maintain physiological function (photosynthesis, grain filling) even under limited water supply, avoiding severe yield loss. [1]

Other acceptable characteristics include resistance to storage pests (weevils) and resistance to common diseases in the region such as maize streak virus.