Modulation of NO 3 - uptake by water-extractable humic substances: involvement of root plasma membrane H+ATPase |
| |
Authors: | Pinton Roberto Cesco Stefano Iacolettig Gabriele Astolfi Stefania Varanini Zeno |
| |
Institution: | (1) Dipartimento di Produzione Vegetale e Tecnologie Agrarie, University of Udine, via delle Scienze 208, I-33 100 Udine, Italy FAX No;(2) Dipartimento di Agrobiologia ed Agrochimica, University of Viterbo, via S. Camillo De Lellis, I-01100 Viterbo, Italy |
| |
Abstract: | The effect of a water extractable humic substances fraction (WEHS) on nitrate uptake and plasma membrane (pm) H+-ATPase activity of maize roots was investigated. Four days old maize root seedlings were exposed for 4 to 24 h to a nutrient
solution containing 200 μ M nitrate in the absence or presence of 5 mg org. C { L
-1 WEHS. Plants exposed to nitrate developed a higher capacity to absorb the anion (induction): the net uptake rate progressively
increased up to 12 h of contact with the solution; thereafter, a decline was observed. When WEHS was present together with
nitrate in the nutrient solution, the induction of nitrate uptake was evident and maximal already 4 h after starting the treatment.
The rate of net nitrate uptake decreased only slightly during the remaining period (4-24 h). Stimulation of net nitrate uptake
rate was also observed when WEHS was added to a nitrogen- or nitrate-free nutrient solution or to a 5 mM CaSO4 solution. The activity of pmH+-ATPase raised upon exposure of the roots to nitrate with the same pattern observed for nitrate uptake. The contemporary presence
of nitrate and WEHS caused a further stimulation of the pmH+-ATPase activity after 4 h treatment. An increase in the enzyme activity was also observed when plants were treated for 4
h in the presence of WEHS in CaSO4, nitrogen- or nitrate-free solutions. However, when nitrate was present the enhancement was even greater. Results support
the idea that the plasma membrane proton pump might be one of the primary targets of the action of humic substances on plant
nutrient acquisition. A role of WEHS in the modulation of nitrate uptake via an interaction with the pm H+-ATPase is also discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. |
| |
Keywords: | H+-ATPase humic substances nitrate uptake nutrient solution Zea mays L |
本文献已被 SpringerLink 等数据库收录! |
|