BBC Earth (Asia) - - Science -

All plants can sur­vive for short pe­ri­ods with­out light. Ob­vi­ously, they need to be able to last through the night, but they can also cope with a longer dark­ness in an emer­gency. If you leave a tent pitched on the same patch of lawn, the grass un­der­neath turns yel­low and spindly. This is an adap­ta­tion, called eti­o­la­tion, which fo­cuses the plant’s re­main­ing re­sources into grow­ing as far as pos­si­ble to try and reach sun­light again. There are also some plants that have lost the power of pho­to­syn­the­sis al­to­gether. The genus Orobanche (com­monly known as ‘broom­rape’) is an ex­am­ple. The plants have no chloro­phyll and get all their nu­tri­ents by par­a­sit­i­cally at­tach­ing to the roots of nearby plants in­stead. Although broom­rape doesn’t har­ness sun­light it­self, it is still in­di­rectly re­liant on the Sun to pro­vide en­ergy to its host plant.

Some other par­a­sitic plants, called my­co­heterotrophs, feed on fungi and these could the­o­ret­i­cally sur­vive in com­plete dark­ness for months or even years. But of course, those fungi in turn get their en­ergy by di­gest­ing dead plants, and in a per­ma­nently dark world, this food source would even­tu­ally run out. No plant can live with­out sun­light for­ever. LV

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