Gene Expression and Physiological Responses of Drought Stressed Creeping Bentgrass Transgenic for an ipt Gene Controlling Cytokinin Synthesis.

Drought symptoms of creeping bentgrass (Agrostis stolonifera L.) such as a reduction of visual turf quality, relative water content, chlorophyll content, electrolyte leakage, and root viability, occur relatively quickly compared to other species. Mechanistically, plants that are able to maintain active growth and adequate levels of aforementioned parameters are deemed more drought tolerant. This study served to evaluate the influence of an ipt transgene controlling cytokinin production and leaf senescence on such physiological drought tolerance characteristics. In addition, young and old leaves and roots were measured independently for comparative analysis of their respective responses to drought for physiological health parameters, hormone content, and expression of the transgene. Plants were grown in a growth chamber in a hydroponics system and drought stress was imposed by incremental additions of polyethyleneglycol (PEG 8000) to gradually reduce the osmotic potential of the growth solution. Plants were sampled for each parameter by separating young (first 2-3 leaves) and old (3-5 leaves) from each stem. Old leaves and roots declined in health more rapidly than their young counterparts, as expected. Independent transgenic lines controlled by senescence or a heat shock promoter were able to sustain chlorophyll content and relative water content for a longer duration than wild type ‘Penncross,’ especially in older leaves.