Tissue shrinkage/growth analyses.
To investigate the distribution of water between vegetative and reproductive tissues as plants dehydrated, we used cameras to simultaneously monitored the shrinkage dynamics of reproductive and vegetative organs, petioles, peduncles, and fruit within individual plants. 5 different plants were measured and exposed to the same dehydration and water potential monitoring as above. Intact proximal regions of S. lycopersicum petioles and peduncles were secured in cavicams as described above. Images were acquired using transmitted light to produce a silhouette every 10 minutes until the plant was fully desiccated (approximately 8 days). Cameras were refocussed every day as the tissue dried. Intact tomato fruit approximately 1cm diameter (older than 7 days) were photographed using a Leica DFC450 digital camera. Single fruit were secured to the stage of a Leica M205A stereomicroscope (Leica Microsystems, Wetzlar, Germany) or a custom-built gantry holding a Nikon lens attached to a Raspberry PI camera and Images taken at intervals of 10 minutes until the plant was fully desiccated.
Images were processed in IMAGEJ (NIH). Image sequences were thresholded to isolate plant tissue from the background. The total thresholded area and fruit diameter were recorded every 50 images and this decrease in size, expressed as a percentage if the original area, was plotted against water potential.
To confirm that a vascular connection was required for fruit growth the growth of tomato fruit was also assessed once fruit were removed from the plant’s vascular supply. A tomato fruit of ~1cm diameter was monitored as above, however once the plant water potential had reached -1MPa, after demonstrating initial positive expansion, the fruit was excised from the plant at the peduncle using a razor blade. Images were captured every 2 minutes until the rest of the plant was fully desiccated.