Due to global climate change and the increase in CO2 levels and a decrease in wa
ID: 92316 • Letter: D
Question
Due to global climate change and the increase in CO2 levels and a decrease in water and plants are having to adapt to the changes. For the following question use and cite at least one peer reviewed source for full credit.
1. While the CO2 levels and the temperature increase, the water levels decrease. What effect will this have on the light reactions? and the Calvin cycle?
3. As the climate in certain areas becomes very hot and very dry explain how plants will need to evolve in order to handle the changes. Make sure to talk about their leaves, roots, and stomata.
Explanation / Answer
Photosynthesis is a series of chemical reactions divided into two stages, the light reactions and the Calvin cycle.
Light reaction:
Photosynthesis begins with the light reactions. It is during these reactions that the energy from sunlight is absorbed by the pigment chlorophyll in the thylakoid membranes of the chloroplast. The energy is then temporarily transferred to two molecules, ATP and NADPH, which are used in the second stage of photosynthesis. ATP and NADPH are generated by two electron transport chains. During the light reactions, water is used and oxygen is produced. These reactions can only occur during daylight as the process needs sunlight to begin. Since water is used in light reaction, the lack of water due to global warming will reduce the rate of light reaction.
Calvin cycle:
The second stage of photosynthesis is the production of glucose from carbon dioxide. This process occurs in a continuous cycle, named after its discover, Melvin Calvin. The Calvin cycle uses CO2 and the energy temporarily stored in ATP and NADPH to make the sugar glucose. An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor.
The following modification needed by the plant to combat hot and dry condition:
Deep Rooted Plants: Some plants have deep tap roots, which can reach even upto water table, in arid climates; hence they are capable of absorbing water from deep soil.
Plants having Deciduous Leaves: Many shrubs and trees of dry climate, such as Acacia nilotica and Capparis decidua have deciduous leaves. But in the majority of the plants the leaves are generally reduced to seeds, as in Casuarina, Ruscus, Asparagus, etc.
Leaves with Sunken Stomata: For example, stomata are found is sunken pits in the common Nerium plant, reducing the rate of transpiration.
Rolling of Leaves: The leaves of many xerophytic grasses, roll tightly under dry conditions. In these grasses, the stomata are combined to the ventral surface of the leaf, so that when the leaf edges roll inward, the stomata are effectively shut away from to outside air. As the stomata are located on the inner surface of the leaf, the air enclosed by the rolled leaf soon becomes saturated with water and the outward diffusion steps, e.g., Ammophila, Erica, Spartina, etc.
http://www.sciencedirect.com/science/article/pii/S1512188716300215
https://www.nps.gov/cany/learn/education/upload/fifthgrade_plantadaptations.pdf