Einfluß von Stickstoffernährung und Wuchsstoffapplikation auf die Knolleninduktion bei Kartoffelpflanzen

Abstract

Influence of nitrogen nutrition and application of growth regulators on tuber initiation in potato plantsIn water culture the effect of continuous and discontinuous N‐nutrition on tuber initiation was investigated. Additional applications of growth regulators on growing stolon tips were carried out.Continuous supply of nitrate or ammonium inhibited completely the tuber initiation in S. tuberosum varieties „Ostara”︁ and „Clivia”︁, The inhibition was compensated by application of CCC and ABA on the stolon tip. In contrast to this stolon application of kinetin and root application of CCC were ineffective. Temporarily damaging of the root system led to tuber initiation even when nitrogen was supplied continuously. In S. andigena grown under short day continuous N supply only delayed the tuber initiation but could not prevent it.Discontinuous N supply promotes tuber initiation in S. tuberosum. A sudden increase in N supply caused „re‐growth”︁ of the tuber, i.e. a stolon was formed on the tuber apex. GA3 application on the growing tuber had the same effect.The effect of N nutrition on tuber initiation can be explained via changing the balance of endogenous growth regulators in general and the physiological aging of the leaves in particular. Discontinuous N supply seems to reduce cytokinin production in roots and therefore accelerates the aging of the leaves. This in turn favours the formation of inhibitors and/or presumably reduces the GA production in the shoot, which will change the balance of the growth regulators in the stolon tip in favour to tuber initiation.