CBSE Class 10 Answered

Most plants require a period of darkness in order to thrive. Even high light plants need some time without light for optimal growth in most cases. Too much or too little light often causes problems.

Plants require a period of dark in order to grow properly. In most cases, the plants need at least eight hours of dark out of every day. The leaves on plants that get too much light begin to get pale. They may end up appearing burnt, and the leaves will ultimately turn brown and die. If the overexposure continues, the entire plant will succumb.

Some plants, such as philodendrons show no growth differences when exposed to 24-hour light, except to keep lower leaves slightly longer than usual. Plants such as coleus and cacti thrive under such conditions. Slow-growing plants, such as orchids, reach maturity faster under continual lighting.

Some tropical plants can do well with constant light. These plants are those from at or near the equator that are used to extremely intense light 12 hours each day. When placed in an environment where there is constant lighting, such as in an office, the perpetual lights lack the intensity of the sunlight at the equator. The longer exposure time compensates for the diminished strength of the light, and these tropical plants will thrive under such conditions.