1363:
Possible Roles of Silicon, Calcium, and Regulated Deficit Irrigation On Poinsettia Plant Quality and Postharvest Performance

Sunday, July 26, 2009: 2:00 PM
Jefferson C (Millennium Hotel St. Louis)
W. Roland Leatherwood, PhD , Department of Horticulture, Cornell University, Ithaca, NY
Neil Mattson , Department of Horticulture, Cornell University, Ithaca, NY
John M. Dole , Department of Horticultural Science, North Carolina State University, Raleigh, NC
The effect of silicon on improving containerized plant quality is an area of active study.  Improved stress tolerance, mechanical strength and disease resistance have been reported for several species, as well as changes in plant architecture and inflorescence size.
To investigate possible beneficial effects of substrate applied Si and Ca in Poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) production.  The treatment design was a factorial arrangement having 2 Ca concentrations, 2 Si concentrations, and 3 irrigation regimes.  We applied 0 and 56 mg · L-1 Si , 0 and 100 mg · L-1 Ca, as part of regular fertigation.  In addition, plants were given 100, 80 and 60% regulated deficit irrigation (RDI).  Regulated deficit volumes were established gravimetrically using several well watered (100%) reference plants.  Plants were evaluated for a variety of factors during production and postharvest storage.
We observed a significant improvement in postharvest water stress tolerance, as measured by degree of wilt, when plants were supplemented with silicon.  Leaf wilt angle was reduced 31% after 5 days of simulated postharvest storage without water.  Regardless of nutrition regime, plants subjected to 60 and 80% optimal irrigation exhibited reduced postharvest wilting compared to well watered plants.  Yet, these plants had significantly smaller bract sizes compared to well watered plants.  Interestingly, bract sizes of well watered plants and RDI plants supplemented with silicon did not differ significantly, which suggests a role for Si in supporting cell expansion under water limiting conditions.
In addition, we found significant differences in disease incidence, height, and branch strength between silicon and calcium supplemented plants, and control plants.