Introduction of Seed Development and Arabidopsis Embryo Development

Introduction of Seed Development and Arabidopsis Embryo Development By Bekah Charney and Thi Nguyen HC 70 AL Spring 2006

What is the life cycle of an Arabidopsis Plant? 2 n Adult Sporophyte Meiosis n n Haploid spores Many mitosis n Adult Gametophyte Mitosis n Gametes 2 n Zygote Many Mitosis 2 n Adult Sporophyte n n Haploid spores

How do seeds form during the life cycle of a plant?

Double Fertilization of cells leads to seed formation

Embryo Development EMBRYO SAC GLOBULAR HEART TORPEDO MATURATION

Globular Stage • Stage which precedes cotyledon development • Embryo proper is spherical • Note the suspensor

Heart Stage • Globular embryo develops into twolobed form • Suspensor acts as an “umbilical cord, ” providing nutrients to the embryo.

Torpedo Stage • Cotyledons and axis grow longer • Embryo may remain straight or become curved

Mature Embryo • Cotyledons curve and provides nutrition to plant, enough to get plant started with photosynthesis • Suspensor disappears • Endosperm has been used for nutrients and now is used up

Mutations that are Lethal to Zygote Lethal to Gamete A a A AA Aa aa Phenotype: live to dead seeds 1: 1 Genotype: AA to Aa 1: 1 Phenotype: live to dead seeds 3: 1 Genotype: AA to Aa 1: 2 A a A AA Aa aa

Acknowledgements • We would like to thank Ria, Jon, Xing. Jun and Tomo for allowing us to use their Nomarski photographs and their assistance in general in helping to make to this presentation • We would also like to thank Mike, Brandon, Jessica, the rest of the HC 70 AL class and Dr. Goldberg for being there for us all quarter!