Comparative studies of the structure and development of vegetative and floral meristems in seed plants

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The use of comparative developmental studies continues to yield important new data because morphological concepts are basic to disciplines such as systematics, physiology, developmental, and molecular biology. These studies also play a complementary role in our understanding of the molecular aspects of plant development by linking observable developmental processes with the activity of specific genes. The proposed approach to plant development, ranging from the molecular level to the whole organ, provides a more comprehensive basis for understanding the evolution and diversity of morphological forms. This program of research has 3 themes: 1- Leaves as partial shoots: Comparisons between early stages of development of a shoot system and compound or complex leaves support to idea that leaves exhibit partial shoot features. Proposed projects include: i) a comparative study of aerial and submerged dissected simple leaves of Water Milfoil complemented with the use of a technique known as in situ hybridization to probe for the activity of genes involved in maintaining an indeterminate state of growth in shoots; ii) the continuation of a comparative study of species with leaves that have multiple levels of branching.2- Floral organ identity in Araceae: Some Aroids have inflorescences characterized by a zone of bisexual flowers between unisexual male (top) and female (bottom) zones. These bisexual flowers represent a unique case where some female organs are replaced by male organs on 1 whorl. Projects include: i) determining the relationships that characterize the substitution of one type of floral organ by another; ii) probing for the activity of floral organ identity genes during early development for comparison with model species.3- Variations in phyllotaxy during development: This project will capture and characterize discontinuous transitions in leaf arrangement in seedlings of Eastern White Cedar in 'real time' as a further step toward understanding the mechanisms involved in these transitions. A tissue culture technique will be developed to look at development in 'real time'.