Effect of Light Intensity on Photosynthesis

Effect of Light Intensity on Photosynthesis

Julie Ann E. Felices

Botany 1 Sec. X-5L

April 13, 2016

A scientific paper submitted in partial fulfillment of the requirements in Botany 1 laboratory under Ms. Ivy Amor F. Lambio, 2nd semester, 2015-2016.

ABSTRACT

This study was conducted to know the effect of varying light intensities on the rate of photosynthesis of a Hydrilla plant. The rate of photosynthesis of the plant was determined using bubble counting method. The bubble is the oxygen produced during the process. The set-up was placed in three areas with different light intensities, with darker light, low light, and strong light. The number of bubbles observed in the control is less than the observed bubbles in the low light. Also, the bubbles in the low light are less than those in the strong light. Thus, the higher the light intensity, the greater the rate of photosynthesis of a Hydrilla plant.

INTRODUCTION

Photosynthesis is one of the two plant physiological processes which occur primarily in leaves (Zafaralla, 2007). It is the process in which solar energy is converted into chemical energy. According to Merriam-Webster (2016), “photosynthesis is the synthesis of chemical compounds with the aid of radiant energy and especially light.” Photosynthesis involves two sets of reactions; the light reactions where chlorophyll molecules absorb solar energy to energize electrons used in ATP production (Roes, 1991). The second is the Calvin cycle reaction where CO2 is taken up and reduced to a carbohydrate that can be converted to glucose, ATP and NADPH from light reactions are also needed. Therefore light is actually one of the essential factors in the process of photosynthesis.

Light intensity is the rate at which the light spreads over a surface of a given area. Light is one of the external factors that affect the rate of photosynthesis.

 The rate of photosynthesis is directly proportional to light intensity (Kent, 2000).

MATERIALS AND METHODS

In this experiment, a Hydrilla sprigs, a beaker, test tube, funnel, water, box, and light source are needed. The Hydrilla sprigs was placed in a large glass funnel such that their freshly cut ends are towards the stem of the funnel. The funnel was inverted into a 500-mL beaker 3/4 filled with water. The test tube was filled with water and was carefully inverted over the funnel stem. [pic 1]

Plate 8a. A set-up to demonstrate                 photosynthesis by the                                 bubble-counting method

This set-up was observed under ordinary room light condition (low light intensity). The oxygen given off by the photosynthesizing sprigs appears in the form of bubbles. A relative estimate of the process of photosynthesis was made by counting the number of bubbles coming out of the funnel regularly per minute time. Next, the set-up was illuminated with strong light (high light intensity). And lastly, the light was put off then the set-up was transferred to a darker part of the room (inside a box). Observations were made and recorded.  

RESULTS AND DISCUSSIONS

Table 8a. The number of oxygen bubbles per minute given off by         photosynthesizing Hydrilla sprigs in high and low light intensities

The table shows the data collected upon the subjecting the set-up in different light intensities. There are three observations conducted per intensity and were averaged to get the approximate number of bubbles evolved. In the exposure of the Hydrilla plant in a darker light, there were no observed bubbles. Upon exposure to low light intensity, the average number of bubbles produced was 435 while with high intensity light, the average number was 482 bubbles.