Manganese deficiency in oats.

E. S. TWYMAN1 Stresses the value of the water-culture technique used by Stout and Arnon2 in investigations into the effects of traces of the heavy metals on plant growth. The demonstration of the rapidity with which grey-speck lesions can be produced in oat seedlings is, however, not new, and directs attention to the need to consider carefully the chemical background to all water-culture investigations. More than fifteen years ago it was shown3,4 that, provided proper precautions were taken to exclude manganese from the culture solutions, grey-speck lesions invariably developed in oat plants in four weeks or less. Recent work by Arnon and Stout5 on the effect of molybdenum on the growth of tomatoes has been confirmed by me6 in regard to oats, so that the response obtained by Twyman to the group of seven elements (aluminium, molybdenum, titanium, vanadium, tungsten, nickel and cobalt) cannot be separated from the response known to be due to one of them.