Journal article

Publication year: 2001

Pages: 165-172

Journal: Journal of Plant Nutrition and Soil Science

Volume number: 164

Issue number: 2

ISSN: 1436-8730

Publisher: Wiley-VCH Verlag

Abstract: 
In a series of experiments, the effect of elevated pH on root growth of different lupin genotypes and lime-tolerant Pisum sativum was assessed. Seedlings were cultivated in pH-controlled but unbuffered nutrient or test solutions with pH 5-8 under constant light or constant darkness. Moderately increased solution pH did not affect root elongation. At high pH, root elongation rates were reduced by less than 35%, L. luteus being most sensitive, in a further experiment, effects of 10 mM bicarbonate (HCO3-) and organic buffers (MES, TES) were examined. Bicarbonate severely affected root elongation of lupins, sensitivity increasing in the order Lupinus albus < L. angustifolius < L. luteus. Since the reduced root elongation was not accompanied by a decreased root weight, specific root weight was increased. Shoot growth was not affected by HCO3-. Addition of organic buffers to alkaline nutrient solution, similarly to HCO3-, reduced elongation of main roots, but not that of laterals. Both treatments increased citrate concentrations in roots of sensitive L. luteus, but not of tolerant L. albus. Other carboxylates were not related to growth inhibition. Xylem exudate pH was always below 5.8, indicating that HCO3- was probably not translocated to the shoot. It is concluded that HCO3- is a key factor for lime-induced growth inhibition of calcifuge lupins, with the roots, not the shoots, being primarily affected.