Plant nitrogen status and co-occurrence of organic and inorganic nitrogen sources influence root uptake by Scots pine seedlings
TREE PHYSIOLOGY 2014; 34(2):205-213
Gruffman L, Jamtgard S, Nasholm T


Insights into how the simultaneous presence of organic and inorganic nitrogen (N) forms influences root absorption will help elucidate the relative importance of these N forms for plant nutrition in the field as well as for nursery cultivation of seedlings. Uptake of the individual N forms arginine, ammonium (NH4+) and nitrate (NO3-) was studied in Scots pine (Pinus sylvestris (L.)) seedlings supplied as single N sources and additionally in mixtures of NO3- and NH4+ or NO3- and arginine. Scots pine seedlings displayed a strong preference for NH4+-N and arginine-N as compared with NO3--N. Thus, NO3- uptake was generally low and decreased in the presence of NH4+ in the high-concentration range (500 mu M N), but not in the presence of arginine. Moreover, uptake of NO3- and NH4+ was lower in seedlings displaying a high internal N status as a result of high N pre-treatment, while arginine uptake was high in seedlings with a high internal N status when previously exposed to organic N. These findings may have practical implications for commercial cultivation of conifers.

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