Final answer:
Plantlike protists are described as autotrophic, meaning they can produce their own food through photosynthesis, similar to plants, though they lack true stems, roots, or leaves.
Step-by-step explanation:
The term that describes all plantlike protists is autotrophic. These organisms, such as algae, kelp, and seaweed, perform photosynthesis to produce their own food by using carbon dioxide and water in the presence of sunlight. Unlike true plants, plant-like protists do not have true stems, roots, or leaves but they still manage to produce their own food in a similar manner to plants.
For classification purposes, protists are divided into different groups based on their nutritional strategies: animal-like protists are heterotrophs, plant-like protists are autotrophic, and fungi-like protists are also heterotrophs. Despite their name, not all protists are closely related, as 'protist' is a term used for any eukaryote that does not fit into the other three kingdoms of plants, animals, or fungi.