Complex sentence: A rhizosphere is a plant-root interface discovered by a German agronomist named Lorenz Hiltner in 1904; this interface exists around the root of a plant and is inhabited by microbe populations in a specialized symbiotic relationship with the plant.
Split into simpler sentences: A rhizosphere is a plant-root soil pool first described by a German agronomist named Lorenz Hiltner; in 1904 he defined the rhizosphere as the soil zone influenced by plant roots and occurs around the root of a plant. The rhizosphere is inhabited by microbe populations in a hypothesized specialized symbiotic relationship with the plant.