Physiology and Evolution of Aluminum Resistance In Oryza sativa
I am primarily interested in plant adaptation to stress. Whether stress is induced by biotic or abiotic factors, plants are unable to escape their environment in the same manner than that of an animal. Plants are forced to adapt and evolve to new and changing environments in order to be successful. Our world is constantly changing and with both human and natural modification to the environment, plants are forced to evolve to survive. In the case of my thesis topic, I am interested in understanding how plants are able to adapt and survive on acid/aluminum soils.
Aluminum is the 3rd most common element in the Earth's crust. In many soils, the aluminum is found in non-toxic compounds and thus does not seem to interfere with plant success. However, in acidic soils >5.0 pH, aluminum is found as the free ion Al+3 and is able to interact with plant root systems and cause aluminum toxicity.
Aluminum/acid soils represent about 40% of worldwide arable land and results in a dramatic loss of yield when sensitive crop varieties are grown. By combining experimentation on the physiology of aluminum resistance in rice and by examining DNA polymorphism and variation in candidate gene regions, I hope to understand how plants adapt to better survive such a stressful environment and also how to improve crops for better utilization in aluminum/acid soils. Cultivated rice, Oryza sativa, is grown in some of the most acidic soils found on the planet and represent a perfect system for understanding how aluminum resistance has evolved.
In this research, 86 different rice genotypes were evaluated for aluminum tolerance by measuring their root growth parameters (root growth rate) in hydroponic media. Of the genotypes examined, Oryza sativa japonica (typically upland dry culture) were consistently more tolerant to aluminum-acid conditions than Oryza sativa indica (lowland submerged culture). This trend may reflect an ease of aluminum stress in submergence culture which has led to subspecies differences in aluminum tolerance ability. As upland cultivars have been and are under more aluminum stressful conditions, they may have evolved to have more normal root growth in these conditions. Additionally, examination of aluminum binding at the root tips of cultivated rice identified that the root apex region is targeted in indica cultivars whereas japonica cultivars were able to block root apex binding. These results suggest a tie between evolutionary history, domestication, and stress physiology in cultivated rice.
