Light has to reach the palisade cells of a leaf. Which feature of the cells covering them makes that possible?
They are packed with the green pigment, which passes light downwards
They are transparent and hold no pigment, so light passes through them✓پاسخ درست
They are thick and waxy, which bends the light down towards the layer below
They open and close to let light in when the plant needs it
توضیح
A covering layer that absorbed light would use it up before the sugar-making cells below ever saw any, so those covering cells stay clear and free of pigment. The idea that they photosynthesise because they face the sun is the common error: they hold no chloroplasts at all, apart from the pair of cells beside each pore.