Poplar may develop both necrosis and distortion. The large, older leaf is normal but the younger leaves were exposed to a high concentration of HF during development. The leaf in the centre is concave-cup shaped but the fluoride concentration at the tip has killed the tissues. In poplar necrotic tissue usually goes black. Eventually the necrotic tissue will fall off, leaving a very distorted shape. The youngest leaf, at the bottom is even more affected. Note that even when poplar shows this degree of injury it still appears to grow well, possibly by producing compensating new leaves.