House plants are colloids solutions elements or compounds?
None of them. They are complex biological structures.
For which organic compounds must information be encoded in DNA for green plants to synthesize the other three compounds?
Yes. Vascular plants can absorb nitrogen compounds such as nitrates from the soil on their own. What plants can't do on their own is fix nitrogen from the air into nitrogen compounds. Some plants including legumes (such as peas, beans, lupins) and casuarinas form symbioses with nitrogen-fixing bacteria to form nitrogen into nitrogen compounds.
Some Bacteria fix nitrogen from the air and give it to plants, others degrade complex organic compound into inorganic elements which are taken by the plants; in return plants synthesize organic compounds used by bacteria for energy. Bacteria associated with plants to fix nitrogen and benefited by the plants for space and energy are called symbiotic bacteria.