If the Hardy-Weinberg principle is valid for this population, calculate how many plants in the field are heterozygous. Use the equations: $p + q = 1$ $p^2 + 2pq + q^2 = 1$ Show your working and give your answer to the nearest whole number.
Suggest two reasons why the student concluded that the flower colour phenotype in $\textit{I. nil}$ has continuous variation.
Scientists examined how stomata respond to changing carbon dioxide ($\text{CO}_2$) concentrations in the beach morning glory, $I.\ pes\text{-}caprae$. The scientists put $I.\ pes\text{-}caprae$ plants into chambers. They recorded the width of open stomata (stomatal apertures) after exposure to different $\text{CO}_2$ concentrations for 40 minutes. Light intensity and temperature were held constant. The link between $\text{CO}_2$ concentration and the mean width of stomatal apertures is shown in Fig. 3.2.
In 2016, a study found the atmospheric $\text{CO}_2$ concentration to be $400\ \mu\text{mol mol}^{-1}$. In the future, climate change may lower 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.
In some conditions, stomatal closure is regulated by abscisic acid. Describe how abscisic acid brings about the closure of stomata.
Scientists are investigating whether abscisic acid could be used in crop treatment to raise yield. Evidence indicates that abscisic acid changes the effect of auxin on elongation growth in plants.
Scientists examined the effect of different concentrations of abscisic acid on root elongation in seedlings of thale cress, $Arabidopsis\ thaliana$. The seedlings were split into four groups: • a control group ($0.0\ \mu\text{mol}$ abscisic acid) • three experimental groups, each given a different concentration of abscisic acid: $0.1\ \mu\text{mol}$, $1.0\ \mu\text{mol}$ or $10.0\ \mu\text{mol}$. For each seedling group, root length was measured for six days during treatment. The rate of root elongation was calculated each day. The results are shown in Fig. 3.3. Using Fig. 3.3, describe the effect of treatment with abscisic acid on the rate of root elongation.
The passage describes how auxin functions in elongation growth in plants. Complete the passage by choosing 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.
Using Fig. 3.3, describe the effect of treatment with abscisic acid on the rate of root elongation.
The passage describes the role of auxin in elongation growth in plants. Complete the passage by using the most appropriate 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.