Question

short pulses of light given to chlorella leaf with dark period​

Answer 1

Explanation:

Introduction

As early as 1953, reports documenting the enhancement of photosynthesis by plants when

exposed to flashing light, as compared to the same photon dose under continuous light,

were published (Kok, 1953; Myers, 1953). Using the unicellular green alga Chlorella, the

effects of varying frequencies and dark/light duration ratios on photosynthetic rates were

described. Such results have kindled research on their role in nature and their application in

various photobioreactors and algal mass culture facilities, aimed at the production of

valuable carotenoids, lipids, and additional products of commercial interest, such as

biodiesel. The present review discusses the characteristics of the fluctuating underwater

light field in natural waters, bioreactors, and ponds, and summarizes their effects on

photosynthesis and growth.

Based on the advances in the understanding of the various mechanisms and processes

affecting the efficiency and yields of photosynthesis, we discuss their interaction with

continuous and intermittent light. The following are examined:

a. Post-illumination enhanced respiration

b. Photodynamic damage to the 32kd protein of Photosystem II (PSII)

c. The xanthophyll cycle

d. Thermal-energy dissipation

e. In addition, the enhancement phenomenon is examined in relation to the intensity of

the ambient light

In the context of the present review, it is appropriate to list and compare the different terms

and definitions used in the description and study of fluctuating light fields (Table 1). In the

following review, the term 'fluctuating light' is used for clarity and consistency.

1.2 Fluctuating light in terrestrial ecosystems

1.2.1 Canopy

In many forests with closed canopies, only a small fraction (0.5-5%) of the solar radiation

incident above the canopy reaches the understory. Understory plants in these forests

experience a highly dynamic light environment, with brief, often unpredictable periods of

direct solar irradiance (sunflecks), punctuating the dim and diffuse background irradiance