A group of horticulturists observed that orchids do not show better growth unless anappropriate fungus lives close to their roots.The given association between orchids and fungus is identified as:

Explanation

The term mycorrhizae refers to a symbiotic association between fungi and the roots of a plant. This relationship is mutualistic, meaning that both the plant and the fungus benefit from the association. In the case of orchids, mycorrhizae are crucial for their growth because the fungi help in the absorption of nutrients and water from the soil, which enhances the plant's growth. This association is different from lichens, which involve a fungus and algae or cyanobacteria, not plant roots. Saprophytic molds decompose dead organic matter and do not engage in mutualistic relationships with living plants. Parasitic mildews extract nutrients from plants, harming them rather than helping them.