Effects of Nitrogen on the Development and Growth of the Potato Plant. 2. The Partitioning of Dry Matter, Nitrogen and Nitrate

Potatoes (Solanum tuberosum L.) were planted in pots in a temperature-controlledglasshouse The treatments consisted of three levels of nitrogensupply, ie 25, 8 and 16 g N per pot (treatments called N1, N2and N3) The accumulation rates of dry matter and nitrogen showedan upper limit of response to nitrogen supply, N3 plants continuedto accumulate dry matter and N at a constant rate for a longerperiod of time than N2 and N1 plants The uptake of nitrogenslowed earlier in time than the rate of dry matter accumulationin all treatments. The proportion of the dry matter in tubersof mature plants was not affected by nitrogen treatment, butthe start of tuber bulking was delayed in the N3 plants Thefinal proportion of total plant nitrogen in the tubers was similarfor all treatments The concentration of nitrogen in the drymatter of mature plants increased with the level of N supplyMaximum haulm weight increased with the level of N supply Apicallateral branches of the first and second order made up largerproportions of the total haulm dry weight and total leaf areaas more nitrogen was supplied. Yet, the distribution of drymatter over stems and leaves was not different between nitrogentreatments Stems were the most responsive to N treatment interms of N concentrations In each of the component organs (stems, leaves, tubers) theconcentration of nitrogen declined with time Fairly strong associationswere observed between the concentrations of N in component organs.The concentration of nitrate in leaves usually increased initiallywith leaf age, peaked and declined. A substantial part of thedifferences between treatments in the concentrations of N inleaf dry matter were attributable to differences in nitrateconcentration Nitrate in stems and tubers fell virtually belowthe limit of detection at total nitrogen concentrations of lessthan 1%, but increased in proportion to total N above that threshold,especially in stems Potato, Solanum tuberosum L, dry matter production, dry matter distribution, nitrogen nutrition, nitrogen distribution, nitrogen concentration