Final answer:
Grime proposed that plants are able to adapt to a broad spectrum of environmental pressures, such as deep ocean pressures, dry conditions, and high levels of radiation. Various studies, including those examining changes in stomatal densities and indexes, support the notion of plants' adaptability to changing environmental conditions including elevated carbon dioxide levels.
Step-by-step explanation:
Grime contended that plants can adapt to a wide array of environmental pressures, including extreme pressures like those at the bottoms of ocean trenches, desiccation, and ionizing radiation. Specific research has shown that the plant Arabidopsis, a member of the Brassica family, developed elevated stomatal densities when grown under elevated CO₂ concentrations, though these changes were not heritable. Meanwhile, Woodward's studies with the Cambridge herbarium demonstrated adaptations in the stomatal index of several trees in response to changing atmospheric CO₂ levels over time. These studies, along with others examining plant adaptations to factors like microgravity and urbanization, highlight the ability of plants to adapt to a variety of environmental stressors.