(a(i))[2]
An adaptation of rice plants that lets them grow in water is the formation of aerenchyma. State the function of aerenchyma.
(a(ii))[1]
State one further way in which rice roots are adapted for life submerged in water.
(a(iii))[3]
Another adaptation in some rice varieties is rapid stem growth. Describe how selective breeding could be used to produce rice varieties with fast-growing stems.
(a(iv))[3]
Auxin is a plant growth hormone that influences the growth of rice stems. Explain how auxin affects the growth of rice stems.
(b)[3]
Explain how $\textit{O. rufipogon}$ and $\textit{O. nivara}$ could have evolved by sympatric speciation.