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Uptake regions of inorganic nitrogen in roots of carob seedlings
Author(s) -
Cruz C.,
Lips S. H.,
MartinsLoução M. A.
Publication year - 1995
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1995.tb00824.x
Subject(s) - ceratonia siliqua , nitrogen , ammonium , chemistry , nutrient , nitrate , ion , botany , horticulture , biology , organic chemistry
Three‐week‐old seedlings of carob ( Ceratonia siliqua L. cv. Mulata) were grown for 9 weeks under different root temperatures (20, 30 and 40°C) at pH values of 5, 7 and 9 with nitrate or ammonium as nitrogen source. Nitrogen uptake rates were determined by depletion from the medium and decreased with distance from the apex. The decline of nitrogen uptake rates along the roots depended on the form of inorganic nitrogen in the medium as well as on pH and temperature, such that the NO − 3 and NH + 4 ions were taken up essentially by the root tips (0–2 cm) through processes requiring energy. The uncharged NH 3 species entered passively, through the mature parts of the root (2–10 cm). Root zone temperature and pH affect the NH + 4 /NH 3 equilibrium in the nutrient solution and, consequently, the uptake areas of the root for these ions. Furthermore. while root tip uptake of nitrogen is energy dependent, uptake through mature root areas is essentially passive and seems to depend on a well developed apparent free space.