[Photosynthesis] 6.How will stomata closure affect photosynthesis?

Plants can regulate the movements of water vapor, O2 and CO2 through the leaf surface. This is accomplished by opening and closing pores, called stomata, usually found on the bottom side of the leaf. Opening and closing of stomata is controlled by specialized cells called guard cells.

The figure below shows a section of the bottom of a typical leaf as seen through a microscope. The stomate exists as the small opening between the pairs of guard cells.

Guard cells can respond to a variety of environmental and physiological stimuli by opening and closing the stomate. For example, under hot, dry conditions stomata of many plants close to help conserve water. Stomata of most plants also close in the dark.

CO2 used during photosynthesis first must pass through stomata into internal spaces within the leaf. It then diffuses into mesophyll cells where it becomes available for photosynthesis.

When the stomata close, CO2 levels drop rapidly within the leaf, inhibiting the light-independent reactions. This then causes photosynthesis to stop.

Stomata closure limit the intake of carbon dioxide which is important for photosynthesis to take place.This factor is more significant in the day where there is sunlight.

[Photosynthesis] 5.How does leaf position on a tree affect photosynthesis?

Plants we see out in the wild display evolutionary adaptions to growth in bright sunshine or shade. Leaves of tree often show developmental adaptions to different conditions. Leaves on the exterior of the canopy are refered to as 'Sun' leaves, and they develop under conditions of direct sunlight. Leaves within the crown of the tree are adapted to the shade created by surrounding leaves thus refering them as 'Shade' leaves. These adaptions include differences in leaf anatomy, metabolism (such as photosynthesis) and shape.

Plants are usually adapted to growth in direct sunlight or shaded conditions. Similar differences are observed among the leaves of large trees; those leaves that develop under the shade of other leaves are anatomically and metabolically different from those that grow on exposed canopy surfaces.

Shade-type leaves typically are thinner, have more surface area, and contain more chlorophyll than those of sun leaves. As a result, shade-leaves (curve B) often are more efficient in harvesting sunlight at low light levels; remember, the slope of the line observed under low light conditions is a measure of photosynthetic efficiency. However, sun-leaves (curve A) display a higher light saturation point and maximum rate of photosynthesis.

[Photosynthesis] 4.How does the light intensity affects the rate of photosynthesis ?

Light is the layman's term for visible radiant energy in the 400 to 700 nm wavelength region of the spectrum. In other words, it is the form of radiant energy (i.e. radiation) that animals can see. It is also the wavelengths of radiant energy that plants use in photosynthesis and for most other reactions that require light.

The rate of photosynthsis in a plant depends on the supply of carbon dioxide, supply of light, supply of water, temperature and various other factors like the amount of chlorophyll.In this blog,we will be setting the supply of light and its intensity as a more prominent factor affecting the rate of photosynthesis .

If the plant is in dim light, but has plenty of CO2, H2O and is warm enough, then it will be light which is limiting the rate of the whole process. If this is the case, then increasing the light will increase the rate of photosynthesis.

Measurement of light intensity
1) photometer or common light meter (cheapest) - measures amount of luminance
Expressed as: a) foot-candle (ft-c) - 1 lumen per square foot b) lux - 1 lumen per square meter
1 foot-candle = 10.76 lux

fig 1 : The relation between carbon dioxide exchange and
light intensity

Fig 1 shows the relation beween carbon dioxide exchange and light intensity.The rate of photosynthesis is show by the carbon dioxide exchange in the graph affected by the light intensity. As we can see , the higher the light intensity , the higher the rate of photosynthesis. However, the rate of photosynthesis will level off at the tip of the curve due to the limited amount of chlorophyll on the leave as well as the limited quantity of light that can be absorbed by the plant for photosynthesis.

[Photosynthesis] 3.What is the process of plants consuming the food ? How is it consumed ?

All living things comsume food . Plants do not move,how do they consume their food?

The process of using food and oxygen to get energy is called respiration. Plants must use the energy they trap in the food to stay alive. That's where respiration comes in. At night, plants take in oxygen and use it to get energy from the food they stored. This is a chemical reaction. This is the same reaction that takes place in animals that eat the plants.

Respiration is essential to provide metabolic energy and carbon skeletons for growth and maintenance. As such, respiration is an essential component of a plant€s carbon budget.

[Photosynthesis] 2.Do all plants use carbon dioxide to make food ?

According to Dr. Galapagos answer ,not all plants use carbon dioxide to make food.

1)Plants that Use Carbon Dioxide (CO2):

Autotrophic Plants

Green plants are completely autotrophic. Autotrophic plants require only solar energy, carbon dioxide, water, and a few minerals to make all the organic compounds necessary to keep themselves going and growing. So all autotrophic plants use carbon dioxide. Carbon dioxide, water, and minerals are all inorganic compounds. Autotrophic plants, then, can get everything they need from inorganic compounds.

Semiparasitic Plants

Some plants can't quite do it all from just water, CO2, and sunlight (and a few other nutrients like nitrogen). Semiparasitic plants have some green parts and can take carbon dioxide from the air, but they can't quite do it all by themselves, so they have to take some nutrients from an autotrophic host plant. In other words, these types of plants actually connect themselves to another plant and take some of the food they need from the host plant.

Insectivorous Plants

Another type of plant that uses carbon dioxide for photosynthesis, but still needs a little something extra, are the insectivorous plants. Examples of these are the venus fly trap and pitcher plants. They catch and slowly digest insects and other unfortunate little animals that fall into their traps. Insectivorous plants can live without catching animals but they are a lot healthier if they can catch an occasional bug .

2) Plants that don't Use Carbon Dioxide

Holoparasitic Plants

Holoparasitic plants are parasites like the semiparasitic plants which means they have to be directly connected to an autotrophic host plant. But these plants have no green parts and can't do any photosynthesis. They have to get all their nutrients, energy, water, and carbon from the host plant they are attached to. So holoparasitic plants don't use carbon dioxide and don't release oxygen into the air.

The Plants Formerly Known as Saprophytes

The other type of plants that don't use CO2 are the parasitic plants we use to call saprophytes. These plants are now called myco-heterophytes. They have a fascinating connection to the trees that feed them. A fungus, called a mycorrhizal fungus, connects the myco-heterophytes to the tree and transfers the nutrients from the host plant to the parasitic plant. The host plant does all the photosynthesis work to make food, then "shares" some of it, unwillingly no doubt, with the parasitic plant. The fungus feeds the parasite. I assume the fungus feeds itself also.

Now , i know that not all plants make food using carbon dioxide

[Photosynthesis] 1.What is photosynthesis ?

Humans and plants are living things .All living things need food in order to survive.Humans buy or cook their own food but plants can neither move nor cook so where do they get their food from ?

They photosynthesis .Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy from sunlight carbon dioxide and water to produce glucose.During the day , plants give out oxygen,as a waste product,it is arguably the most important biochemical pathway known; nearly all life depends on it. Chlorophyll in the green leaves help the plant to make food .Plants respire both during the day and at night.They only photosynthesis during the day or in the presence of light .

Photosynthesis occurs in two stages. In the first phase light-dependent reactions or photosynthetic reactions capture the energy of light and use it to make high-energy molecules. During the second phase, the light-independent reactions use the high-energy molecules to capture carbon dioxide (CO2) and make the precursors of glucose.

carbon dioxide + water + light energy → glucose + oxygen + water