Explore how light intensity affects leaf chlorophyll, nitrogen content and light capture in Alocasia, Spinacia and Phaseolus for IB Biology SL B4.2.11.
The nitrogen content of a leaf is mainly due to the proteins contained in the chloroplasts. These proteins are either in the thylakoids or in the stroma, where most enzymes are found. The quantity of nitrogen from the thylakoids is directly proportional to the amount of chlorophyll; a ratio of approximately 50 mmol nitrogen : 1 mmol chlorophyll would represent 100 % of the leaf nitrogen content. Scientists hypothesized that the higher leaf percentage nitrogen content resulting from a decrease in light intensity is due mainly to an increase in chlorophyll in many plant species, three of which are represented in the following graph.
State the difference in chlorophyll content for Phaseolus between high and low light intensity, giving the units.
State the percentage value of total leaf nitrogen in chlorophyll for Spinacia at low light intensity.
Suggest one advantage for plants to increase their leaf chlorophyll content per surface area when light intensity is lower.
Evaluate the hypothesis that lower light intensity increases thylakoid nitrogen.