If the Hardy-Weinberg principle is assumed to apply to this population, calculate how many plants in the field are heterozygous. Use the equations $p + q = 1$ and $p^2 + 2pq + q^2 = 1$. Show your working and round your answer to the nearest whole number.
Suggest two reasons why the student concluded that flower colour phenotype in \textit{I. nil} shows continuous variation.
Scientists investigated how stomata respond to changes in carbon dioxide ($\text{CO}_2$) concentration in the beach morning glory, $I. \, pes\text{-}caprae$. The scientists placed $I. \, pes\text{-}caprae$ plants in chambers. After exposure to different $\text{CO}_2$ concentrations for 40 minutes, they measured the width of open stomata (stomatal apertures). Light intensity and temperature were kept constant. Fig. 3.2 shows the relationship between $\text{CO}_2$ concentration and the mean width of stomatal apertures.
In 2016, a study recorded the atmospheric $\text{CO}_2$ concentration as $400\,\mu\text{mol mol}^{-1}$. In the future, climate change may reduce water availability and raise atmospheric $\text{CO}_2$ concentrations in some habitats. Suggest how the stomatal response shown in Fig. 3.2 would help $I. \, pes\text{-}caprae$ survive the effects of climate change.
Under some conditions, stomatal closure is controlled by abscisic acid. Describe how abscisic acid brings about the closure of stomata.
Scientists are investigating whether abscisic acid could be applied in crop treatment to increase yield. Evidence indicates that abscisic acid alters the effect of auxin on elongation growth in plants.
With reference to Fig. 3.3, describe the effect of abscisic acid treatment on the rate of root elongation.
The passage describes the role of auxin in elongation growth in plants. Complete the passage using the most suitable scientific terms. The binding of auxin to receptors causes ........................ to be pumped into cell walls. This activates proteins called expansins, which disrupt the links between ........................ microfibrils. The cell walls are then able to expand.
With reference to Fig. 3.3, describe the effect of abscisic acid treatment on the rate of root elongation.
The passage describes the role of auxin in elongation growth in plants. Complete the passage using the most suitable scientific terms. The binding of auxin to receptors causes __________ to be pumped into cell walls. This activates proteins called expansins, which break the links between __________ microfibrils. The cell walls are then able to expand.