Question

Your evil roommate creates a device that slows the rate of rotation of planet Earth from a 24-hour period of rotation to a 48-hour period of rotation. Holy cow evil roommate, this is extreme! Given that each day is now 48 hours long, predict how the difference between daytime high and nighttime low temperatures at the equator would change. How do you think this would affect the plants growing at the equator?

Answer 1

If the earth takes 48 hours to complete one rotation on its axis then it means we will have 24 hrs of daylight and 24 hrs of darkness. The speed with which the rotates will also become half as slow. This means the exposure to sunlight will be doubled, not only in terms of time but but also in intensity. In such a condition, life will not be possible on the earth because during the daytime the peak temperature will be twice as high as normal and during night time the temperature will be twice as low as the normal temperature.

But , let us see what would be the effect on plant growth in such a hypothetical situation.

Plants require light for optimum growth and development. Light is the source of energy for photosynthesis. Each plant species starts the process of photosynthesis at different light energy levels, which is called the light compensation point. This point starts when the oxygen produced during photosynthesis is more than that used by the plant for respiration.

However, as the light intensity increases, the rate of photosynthesis reaches reaches a maximum point after which it does not increase. This is called the light saturation point. When this point is reached , photosynthesis rate stagnates.

Now, in the above scenario. both, light compensation point and light saturation point, will be achieved earlier than normal. Along with this, the increased duration of light will affect the plant adversely.

The other factor affecting plants is the quality of light. The sun emits wavelengths between 280 and 2800nm. And light is made up of different wavelengths of light, each of which has a different effect on plants.

* Ultraviolet light causes DNA damage, reduces photosynthesis rate, flowering and pollination decreases and seed development is affected.

* Blue light is responsible for vegetative and leaf growth and photosynthesis is very efficient in this wavelength of light.

* Red light is important for the regulation of flowering and fruiting and photosynthesis is optimum in this wavelength.

The extended daytime will result in overexposure to plants to the sunlight affecting each function of the plant.

Photoperiod or Light Duration directly impacts flowering and hence fruit bearing capacity of the plant. There are three categories-- * short day plants

* long day plants, and

* day neutral plants

Since the photoperiod will change, the effect on flowering and fruit bearing capacity will be directly affected.