A study of propagule physiology during adventitious root development (and other “interesting” works)
Martin, Michael Terry
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To remain competitive, nursery and/or greenhouse producers must be able to reduce cost and/or increase production. In vegetative propagation, this can be accomplished by increasing success rates (rooting percentages) of propagules, increasing the speed of propagule production and/or producing higher quality propagules. To accomplish these goals, a thorough understanding of the adventitious root development (ARD) process and propagule physiology is required. ARD allows for the asexual production of genetically uniform plant material, ensuring each propagule is genetically identical to its stock plant. There are many knowledge gaps relating to ARD physiology. By attempting to fill these gaps, and gain an understanding of the physiological processes that are occurring during ARD, producers can potentially reduce cost while increasing production. This study examines how water potential and net photosynthesis of propagules relate to stock plants in an effort to discern how these two factors relate to ARD and what influence they may exert on the ARD process (or vice-versa). This study also attempts to identify the source of carbon utilized to form adventitious roots during ARD, with the goal of improving carbohydrate availability during ARD. Additionally this study evaluates nutrient utilization in propagules during ARD to determine what nutrients may play a role in this process. Finally, this study endeavors to develop a propagation protocol for seed germination of Amsonia tabernaemontana, an underused, highly ornamental plant native to the southeastern U.S., with hopes of increasing its presence in the nursery trade. From this research, it was concluded that propagules under intermittent misting successfully maintained water (Ψ), osmotic (Ψs) and turgor potential (Ψp) values and were not water stressed. Additionally, net photosynthesis did occur in leafy propagules before adventitious roots appeared and increased in some species after adventitious roots appeared. Also, carbon utilized for ARD was initially provided by both reserve carbohydrates produced prior to propagule severance and newly produced photosynthates. Furthermore, N, P, K, S and Zn were utilized at greater quantities than other nutrients during ARD. Finally, an effective propagation protocol was developed for Amsonia tabernaemontana, including seed scarification by removal of one end of the seed coat combined with imbibition.