CHANGES IN PEACH TREES (cv. RED HAVEN) ATTACKED BY TAPHRINA DEFORMANS, WITH PARTICULAR REFERENCE TO NITROGEN METABOLISM IN INFECTED AND NON-INFECTED LEAVES

Abstract

Some of the changes induced by Taphrina deformans on metabolism (particularly the nitrogen metabolism) of peach leaves were studied. Observations were as follows. (1) Dry weight diminishes in the infected tissues, especially at the end of the cycle, whereas it remains almost unchanged in the non-infected tissues of the diseased plant. (2) Initially, the amount of total nitrogen, per gram of dry substance is clearly greater in the infected tissues than in the control, then it becomes lower during the differentiation of the asci, especially at the stage of full sporulation. Similar variations occur also, in a more attenuated form, in the non-infected tissues. (3) A considerable increase of the glycolytic activity is observed in the infected tissue especially during the period preceding the differentiation of the asci, and an increase of respiration, even though much more restricted, is observed also in the next period. In non-invaded tissues, an increase of glycolysis is noted along with a diminution of respiration. (4) The non-infected leaves weigh more than those of the control until the differentiation of the asci; after it, they have a clear drop up to the maturity of the asci, and a further revival at the end of the disease. (5) In the infected tissues, the content of free amino acids is always higher than in the control (with a maximum after sporulation), whereas in the non-infected ones it is generally lower. (6) The more important alterations in the pool of the free amino acids in invaded tissues consist in a scarcity, in percentage of the total, of alanine and glutamic acid, especially at the end of the disease, whereas proline, ornithine, glycine, and others increase, especially during the incubation period. In particular the glutamine–asparagines– threonine group reaches the highest value when sporulation has occurred. In the non-invaded tissues, the changes are more restricted. (7) The content of protein amino acids in infected tissues is generally lower than in the control, especially in the last phases of infection whereas in the non-invaded parts it is generally higher, except in differentiation of the asci. (8) In the infected tissue, the alterations of the quantitative relationships between the single protein amino acids (in percentage of the total) are not very great, but some diminutions and increases are recorded (diminution of alanine, glycine, leucine, etc.; increase of lysine, histidine, etc.); in the non-infected tissues, no noteworthy alterations were observed.