Premium
Gas and ion exchanges in wheat roots after nitrogen supply
Author(s) -
Barneix Atilio J.,
Breteler Hans,
Geijn Siebe C.
Publication year - 1984
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.1399-3054.1984.tb06340.x
Subject(s) - chemistry , respiration , nitrogen , nitrate , carbon dioxide , zoology , oxygen , botany , biology , organic chemistry
Wheat ( Triticum aestivum L. cv. Sicco) was grown for 10 days on CaSO 4 (0.5 mmol dm −3 ) and then exposed for 2 days to various nitrogenous salts in an apparatus designed to measure the exchange of O 2 and CO 2 , at constant pH and pNO 3 . Nitrate salts (KNO 3 at 0.5 and Ca(NO 3 ) 2 at 0.25 and 1 mmol dm −3 ) caused a transient increase (40–50%) in both O 2 uptake and CO 2 release by the roots. The rate of gas exchange was nearly doubled by (NH 4 ) 2 SO 4 (0.25 mmol dm −3 ). Respiration was constant in roots kept on CaSO 4 or given KCl. In CaSO 4 the content of water‐soluble sugars in roots fell by about 15% day −1 . The pletion of soluble sugars was higher with NO 3 − and NH 4 + (40 and 30% day −1 , respectively). At most 10 to 20% of the released CO 2 is involved in HCO 3 N − NO 3 − exchange and this fraction represents at most 10% of the total carbon imported or 30% of the net carbon gain by the roots. The contribution of the non‐phosphorylating “alternative” route to total root respiration was 15% in CaSO 4 and over 40% with NH 4 + In NO 3 − the roots respired exclusively via the cytochrome route. Increased respiration at decreased efficiency in roots of NH 4 + plants may be due to an overproduction of NADH. Our data support the contention that excess NADH as a “by‐product” of the formation of carboxylates in the citrate cycle can be disposed of in an alternative respiratory pathway during NH 4 + nutrition.