Root respiration associated with ammonium and nitrate absorption and assimilation by barley.
نویسندگان
چکیده
We examined nitrate assimilation and root gas fluxes in a wild-type barley (Hordeum vulgare L. cv Steptoe), a mutant (nar1a) deficient in NADH nitrate reductase, and a mutant (nar1a;nar7w) deficient in both NADH and NAD(P)H nitrate reductases. Estimates of in vivo nitrate assimilation from excised roots and whole plants indicated that the nar1a mutation influences assimilation only in the shoot and that exposure to NO(3) (-) induced shoot nitrate reduction more slowly than root nitrate reduction in all three genotypes. When plants that had been deprived of nitrogen for several days were exposed to ammonium, root carbon dioxide evolution and oxygen consumption increased markedly, but respiratory quotient-the ratio of carbon dioxide evolved to oxygen consumed-did not change. A shift from ammonium to nitrate nutrition stimulated root carbon dioxide evolution slightly and inhibited oxygen consumption in the wild type and nar1a mutant, but had negligible effects on root gas fluxes in the nar1a;nar7w mutant. These results indicate that, under NH(4) (+) nutrition, 14% of root carbon catabolism is coupled to NH(4) (+) absorption and assimilation and that, under NO(3) (-) nutrition, 5% of root carbon catabolism is coupled to NO(3) (-) absorption, 15% to NO(3) (-) assimilation, and 3% to NH(4) (+) assimilation. The additional energy requirements of NO(3) (-) assimilation appear to diminish root mitochondrial electron transport. Thus, the energy requirements of NH(4) (+) and NO(3) (-) absorption and assimilation constitute a significant portion of root respiration.
منابع مشابه
Root Respiration Associated with Ammonium and Nitrate Absorption and Assimilation by Barley ' Arnold
We examined nitrate assimilation and root gas fluxes in a wildtype barley (Hordeum vulgare L. cv Steptoe), a mutant (narla) deficient in NADH nitrate reductase, and a mutant (narla;nar7w) deficient in both NADH and NAD(P)H nitrate reductases. Estimates of in vivo nitrate assimilation from excised roots and whole plants indicated that the narla mutation influences assimilation only in the shoot ...
متن کاملRoot excision decreases nutrient absorption and gas fluxes.
The roots of barley plants (Hordeum vulgare L. cv Steptoe) were monitored before and after excision for net uptake of carbon dioxide, oxygen, ammonium, potassium, nitrate, and chloride and for their content of sucrose, glucose, fructose, and malic acid. All fluxes began to attenuate within 2 hours after excision. Net potassium uptake returned to control levels 6 hours after excision, but carbon...
متن کاملRoot respiration associated with nitrate assimilation by cowpea.
Nitrate uptake by roots of cowpea (Vigna unguiculata) was measured using (15)NO(3) (-), and the energy cost to the root was estimated by respirometry. Roots of 8-day-old cowpea seedlings respired 0.6 to 0.8 milligram CO(2) per plant per hour for growth and maintenance. Adding 10 millimolar NO(3) (-) to the root medium increased respiration by 20 to 30% during the following 6 hours. This increas...
متن کاملSeed germination, vegetative growth and concentration of some elements in French marigold (Tageta patula) as influenced by salinity and ammonium nitrate
Marigold has special importance and application in landscape designing. Nowadays, various species and cultivars of this plant are grown in many climates, where different environmental stresses such as freezing, salinity and drought can lead to vegetative disorders. This study was carried out to investigate the interactions between salinity and ammonium nitrate on seed germination, vegetative gr...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Plant physiology
دوره 99 4 شماره
صفحات -
تاریخ انتشار 1992