Ozone on Long Island threatens plant growth

The responses of cloned ozone-sensitive and ozone-tolerant white clover plants to ground ozone concentration were studied, though Margaret McGrath, who carried out the research, says that the effects of the pollutant appear to be a warning of a wider threat.

“On hot summer days, the air just hangs over the island,” said McGrath. “Combine that with the intense ultraviolet rays and the greater New York City pollutants in the air, and you have a recipe for a lot of high ozone days. These results document that ozone is high enough to greatly reduce growth and yield of sensitive plants on Long Island, where important agriculture in New York is located.”

Ozone enters the plants through stomata in the leaves, which means that any activity promoting the opening of stomata, such as irrigation, increases the risk of ozone injury to plants. According to McGrath, as causes deleterious effects on photosynthesis, the rate of plant production, flowering and yield. As yet, the processes are not well understood, but ozone also influences the incidence of pathogens and pests, as well as decreasing carbon flow to the root, stunting root growth.

“We need to pay attention to the amount of ground-level or ambient ozone,” said McGrath. “There used to be a lot of spinach grown on Long Island. Not anymore. Spinach is very sensitive to ozone, which causes spotting on leaves and making them unmarketable. Acute injury routinely occurs on other Long Island crops, including grapes, pumpkins, watermelons and tomatoes. It’s difficult to assess the impact on yield and injury to the plant’s photosynthetic tissue. That’s why scientists are developing and using indicator systems such as white clover.”

McGrath found that in 1998, ground ozone levels were greater than 80 parts per billion (ppb) for 121 hours, increasing to 184 hours in 1999. In 1998, the highest ozone levels were reached on 26 June, when concentrations peaked at 129 ppb, peaking in 1999 on 7 June, at 123 ppb.

In 1998, the ozone-sensitive and the ozone-tolerant white clover plants grew at a similar rate through the spring until just before the start of summer. Through late summer, the ozone-sensitive clover experienced a 24% reduction in growth rate. In 1999, the growth of sensitive clover was reduced by 27% throughout the summer.