Photon costs of shoot and root NO3−, and root NH4+, assimilation in terrestrial vascular plants considering associated pH regulation, osmotic and ontogenetic effects
- Publisher:
- Springer Nature
- Publication Type:
- Journal Article
- Citation:
- Photosynthesis Research, 2022, 155, (2), pp. 127-137
- Issue Date:
- 2022-11-23
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| s11120-022-00975-y.pdf | Published version | 762.36 kB |
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The photon costs of photoreduction/assimilation of nitrate (NO3−) into organic nitrogen in shoots and respiratory driven NO3− and NH4+ assimilation in roots are compared for terrestrial vascular plants, considering associated pH regulation, osmotic and ontogenetic effects. Different mechanisms of neutralisation of the hydroxyl (OH−) ion necessarily generated in shoot NO3− assimilation are considered. Photoreduction/assimilation of NO3− in shoots with malic acid synthesis and either accumulation of malate in leaf vacuoles or transport of malate to roots and catabolism there have a similar cost which is around 35% less than that for root NO3− assimilation and around 20% less than that for photoreduction/assimilation of NO3−, oxalate production and storage of Ca oxalate in leaf vacuoles. The photon cost of root NH4+ assimilation with H+ efflux to the root medium is around 70% less than that of root NO3− assimilation. These differences in photon cost must be considered in the context of the use of a combination of locations of NO3− assimilation and mechanisms of acid–base regulation, and a maximum of 4.9–9.1% of total photon absorption needed for growth and maintenance that is devoted to NO3− assimilation and acid–base regulation.
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