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STAN R. SZAREK Associate Professor Ph.D., University of California, Riverside Phone: (480) 965-7750 Send e-mail to szarek@asu.edu

Stan Szarek, came to Arizona State University in 1974 after completing graduate studies at the Riverside Campus of the University of California. Dr. Szarek supervises a laboratory investigating desert plant adaptations: physiological, morphological and reproductive. Most of his work is with succulent plants and annuals of hot deserts.

Research Question

Is there a physiological basis for the dominance of non seed-producing, triploid populations of Jumping Cholla in the Sonoran Desert?

Previous Observations

Plants of Opuntia bigelovii (Cactaceae) occur in Arizona and northern Baja California, Mexico. The majority of stands inventoried by Baker and Pinkava (1987) are triploid (2n = 33). Two regions contain diploid populations, where somatic tissue is 2n = 22. One of these is 40 km east of campus.
Triploidy is associated with the loss of seed production and, hence, the absence of successful sexual reproduction.Triploid populations are maintained by the establishment and survival of clones (detached "jointed stems").
Since polyploidy increases the size of cells in plants (e.g., Lewis, 1980), and the metabolism rate of cactus cells increases proportionally with cell size (e.g., Nobel & Hartsock, 1990), then differences in ploidy levels between individuals of Jumping Cholla may modify their comparative physiology

Experimentation

Establish a long-term, common garden experiment with the two genotypes. Separate cohorts will receive either natural precipitation or supplemental drip irrigation. Periodically monitor select parameters: night time acidification; day time internal CO2 concentrations; cuticular waxes and conductance. Conduct separate short-term stude of rooting onset and frequency by detached stems.

Selected Publications

Szarek S R (2004) Scarity-driven evolution in photosynthesis: photosynthetic pathways. In: Encyclopledia of Plant & Crop Science. Marcel-Dekker Publishers. New York, New York.