As temperatures have been on the rise this past week you may have noticed corn starting to react to the temperatures. Because of the hot temperature corn may begin to curl its leaves during the hottest part of the day in order to conserve moisture. By conserving moisture it will also begin to slow transpiration rates in the plant, which means it will start to grow less quickly. This slowing of transpiration decreases the rate of photosynthesis in the plant meaning less sugars are produced, which limits its growth. The thing is that different varieties respond differently to heat and some will curl their leaves quicker than others. A quicker response can be a bad thing if the heat and/or drought stress ends relatively quickly because this means that growth was limited during that short time. On the flip side it can also be a good thing if the stress persists for a long time. This is because the plant is attempting to conserve water, so, if a plant is fast to leaf curl this means that it has been more efficient with its water, which leads to a higher yield. This is something that varies from hybrid to hybrid and different hybrids have different resistances to heat stress. Some hybrids could have leaf curling very severely but end up yielding rather high if it has a high tolerance for heat. All in all the amount of heat damage is related to the length of high temperatures and low rainfall as well as the hybrid of choice.