Date Approved

2-2014

Graduate Degree Type

Thesis

Degree Name

Cell and Molecular Biology (M.S.)

Degree Program

Cell and Molecular Biology

Abstract

Orchidaceae as the most diverse family of flowering plants are endangered due to losing habitats or destruction of their unique symbiotic living style. Long-term seed storage banks can be a solution for threatened plant species but the stored seeds must tolerate extreme drying and cold. This ability is acquired during the last stage (maturation drying) of seed development and is correlated with a decline in water content and expression of the Late Embryogenesis Abundant (LEA) protein genes. Our goal is to investigate if premature orchid seeds can be artificially induced to become desiccation tolerant and the potential role of LEA genes in this process. In this work I monitored changes in water content, germinability, desiccation tolerance and LEA protein gene expression in seeds undergoing artificial drying in Phalaenopsis amabilis. Seeds were processed in 4-day Slow Drying (SD) treatment where they are placed in atmospheres of progressively lower relative humidity and High Relative Humidity (HRH) control where they are placed above water. During SD, seeds maintained their starting moisture content of 70% for 3 days, and then dried to 10-15% moisture on the 4th day. Seeds that had undergone SD become desiccation tolerant but seeds in the HRH control did not. Transcript level of all three LEA genes we’ve studied (TG1: Group4 LEA; TG2: group3 LEA; Dehydrin: Group2 LEA) increased after excision in both treatments but the transcript level of LEA genes from SD treatment were higher than control group. Our results suggest that premature seeds of Phalaenopsis amabilis can tolerate desiccation by appropriate post-harvest treatments and the accumulation of LEA proteins may contribute to the tolerance of desiccation.

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