Professor Todd Dawson

Department of Integrative Biology

"Ontogenetic Physiology: Comparative Physiology of Cotyledons and Mature Leaves in Cotton"

The amount of information known about the physiology of seedlings is very small, yet this stage of development is vital to plant establishment from seed.  The cotyledons,  or first leaves from the embryo, are the first source of positive carbon gain for young germinants. This study compares the physiology of cotyledons and mature leaves of cotton, Gossypium hirsutum (Malvaceae) . Combined with atmospheric carbon dioxide, and solar energy, water transported from the soil is essential to carbon gain (photosynthesis) in the leaves, ultimately supplying carbon for  all plant growth. Thus water transport is vital to survival.  Here we present data on the densities and dimensions of stomata (pores that regulate water loss), , vein density (the density of water transporting tissues in leaves and cotyledons), and the amount of water-conducting xylem in the petioles of mature leaves and in the cotyledon stem. In addition, we measured diurnal variation in the velocity of water transport through stems and petioles. These results will be among the first comparing water transport physiology of cotyledons and mature leaves to provide valuable insight into the ontogenetic changes in physiology from early seedlings to adults.

Ray is a Laney College student with a 3.915 accumulative GPA. She wants to major in Biological Systems Engineering at UC Davis, and be a consultant to agriculture and cities for bioremediation installations.