veloping too little of its vital green coloring material, chlo- 
rophyll. Veins are the last part of the leaf to fade. 
Chlorotic plants develop additional symptoms of distress, varying to 
some extent with the plant species and the growing conditions. Among 
these further symptoms are mottled leaves, meager bud development, and 
dieback of twigs and even large branches. A combination of symptoms 
often points plainly to a specific nutrient which the plant lacks. 
As chlorotic plants weaken, their yields of flowers, fruit, or other 
expected products may become disappointing in quantity and quality. A 
serious chlorosis may kill a plant.In ornamentals and turf, the disfigured 
foliage is in itself cause for concern. 
Plants may become chlorotic for want of essential nutrients other 
than metals, but the specific deficiencies discussed here are limited to 
those which the chelates are helping to overcome. Chelates used in agri- 
cultural research have been most effective in keeping iron and zinc water- 
soluble, and therein lies their most promising value to growers. Of the 
nutrient metal deficiencies that damage plants, a lack of soluble iron is the 
hardest for plant growers to correct; zinc perhaps second. 
Causes of Plant Chlorosis 
Tracing the originating and contributing causes of a plant chlorosis in 
order to provide suitable treatment generally reveals a chain of imbal- 
ances in the soil. 
Chlorotic plants are sometimes growing in soil that is naturally poor 
in the nutrient they lack. This simple chain of cause and effect, however, 
occurs infrequently. 
Far more often, plants are starved for a metal although growing in 
soil abundantly supplied. In this paradoxical state, physical and chemical 
influences in the soil are so great as to prevent the plants from getting 
even their small requirements of the needed metal. 
Following are adverse conditions which most frequently start chloro- 
sis or make it more serious: 
* A soil may be naturally overstocked with some mineral. Calcar- 
eous soils, for example, have accumulated lime and other ele- 
ments intheir formation, and these elements interfere with nutrient 
iron to such an extent that many species and varieties of plants be- 
come chlorotic in these soils. 
* Overwatering or sudden heavyrains may launch physical and chem- 
ical changes in naturally calcareous soils, decreasing the soluble 
om Supply. 
