Effect of Ammonium to Nitrate Ratio on Growth and Anthocyanin Development of Perennial Ryegrass Cultivars1

Improved methods of determining cultivar purity of perennial ryegrass, Lolium perenne L., seed lots, are needed. We conducted studies to find characteristics in which cultivars might differ. Seedlings were grown in sand and were supplied with solutions in which 0, 25, 50, 75, or 100% of the N was NH4 and the remainder was NO3. Growth and anthocyanin development were affected by ratio of ammonium to nitrate. Cultivars differed in both characteristics. Growth, as determined by tiller height, was greatest when plants were grown with 25% of the N as NH4. Anthocyanin development, as determined by percentage of the tiller height showing red color, was greatest when plants were grown with a solution in which 100% of the N was NH4. Cultivar differences in tiller height were greatest when plants were grown with 25% of the N as NH4. Cultivar differences in anthocyanin development were greatest when plants were grown with 75% of the N as NH4. With this solution, cultivars differed in percentage of plants in which red color extended the entire length of the tillers. Both anthocyanin development and tiller height were useful in determining cultivar purity of seed lots.