Issue link: https://read.dmtmag.com/i/705606
6 2 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 016 w w w. v w m m e d i a . c o m observed the berry and vine xylem (part of the vascular system) with dyed water. The research showed that, before ripening, berries were like balloons. The green berries contracted and expanded from drought stress and re-watering. But after veraison, when Biondi tried to make berries explode by forcing massive amounts of water through the roots via a root pres- sure chamber — so much water that leaves were dripping wet — there was no diameter change for berries with sugar concentrations above 11 °Brix. When Biondi and Zhang used red-dyed water to observe the vine's xylem, they found that dye moved less into the berry during ripening, which supports common textbook wisdom that the xylem loses functionality at veraison. But when red dye was put into the rear end of the berry to trace outflow, there was surprising water move- ments found that overhead sprin- klers could be similar to rainfall during berry ripening and induce berry cracking, although cracking is variety-dependent. Once a berry is cracked, its volume can increase and sugar can rapidly be leached from the pulp. But irrigation applied to the vine after veraison through drip or flood will not increase berry size, will not decrease sugars and isn't detrimen- tal to fruit quality, he says. BALLOONS, RED DYE Keller's dilution theory research, which began in earnest in 2004 and has involved a variety of graduate students, has turned into a contin- uum of research projects, with sur- prising and startling results. Students Marco Biondi and Yun Zhang monitored berry diameter with electronic sensors, pressurized vines to study water movement and WSU postdoctoral research associate Yun Zhang works with Markus Keller to continue their research.