Silicon supplements used on sunflowers grown in greenhouse environments do have some benefits, but they also harm plants, scientists have said.
Drs. Sophia Kamenidou and Todd J. Cavins, formerly of the Department of Horticulture and Landscape Architecture at Oklahoma State University, say that their study is different from previous studies that concentrated mainly on the disease suppression in hydroponic vegetable production, for it also brings to light the detrimental effects of high silicon concentrations.
"In greenhouse production, most floricultural crops are cultivated in soilless substrates, which often supply limited amounts of plant-available silicon. The goal of this study was to determine the effects of silicon supplementation on greenhouse-produced ornamental sunflower (Helianthus annuus L. 'Ring of Fire')," said Cavins.
"This is one of the first studies to highlight supplemental silicon impact on horticultural traits. Most previous research on silicon has focused on disease suppression in hydroponic vegetable production. This is also one of the few examples of detrimental effects seen from high silicon concentrations," the researcher added.
Published in the journal HortScience, the study report says that depending on the source and concentration of silicon used, several horticultural traits were improved as a result of silicon supplementation.
"We observed thick, straight stems, increased flower and stem diameters, and increased height in some of the treatments, upgrading sunflower quality compared with untreated controls," Cavins said.
However, growth abnormalities were observed when concentrations of silicon at 100 and 200 mg per litre were supplied as potassium silicate substrate drenches. In these treatments, plants appeared stunted with deformed flowers and were delayed in flowering. Consequently, the effects of silicon supplementation on greenhouse-produced sunflowers can vary from beneficial to detrimental depending on the applied source and concentration," Cavins added.
Summing up the outcomes of the study, Cavins said: "Silicon is a key component in mineral soil, but it has been overlooked for years since it is not considered an essential element for plant growth and development. Sunflowers are capable of accumulating silicon from multiple sources and we found major benefits to some silicon supplements, such as increased stem diameter and improved quality."