Plant Nitrogen Nutrition and Transport

Abstract

Nitrogen (N) is a major plant nutrient and is available in soil chiefly as nitrate (NO 3 − ), ammonium and amino acids. N is acquired through roots and then transported around the plant or it can be combined with carbon to produce amino acids (assimilation) before being redistributed. Most plant cells can assimilate N and any not required for growth is stored as protein. Reserve N can be accumulated as the photosynthetic enzyme Rubisco and species‐specific storage proteins in vegetative tissue or seed endosperm. Cellular storage of NO 3 − occurs in the vacuole, where it is important for driving osmotic expansion growth. The amount of these stored forms defines a plant's N status. Some structural materials like lignin contain a high proportion of N, but this is not stored and is not remobilised. Some plants form a symbiotic relationship with bacteria in specialised nodules to enable the direct assimilation of gaseous N. Key Concepts: Nitrogen supply limits plant growth in almost all natural environments. The soil available form of N depends on factors like soil type, weather and temperature with NO 3 − dominating temperate climates. Some plants form a specialised symbiosis with bacteria to fix atmospheric N. Agriculture includes the addition of N fertiliser to optimise yield. Regulation of plant carbon and N metabolism is carefully coordinated for normal growth and development. Changes in plant N supply trigger alterations in a huge number of genes resulting in changes in morphology, growth rate and development. A change in the phosphorylation status of some plasma membrane NO 3 − and ammonium transporter proteins provides a receptor mechanism that links uptake to external availability.

Drought history affects grassland plant and microbial carbon turnover during and after a subsequent drought event

“…However, to our surprise, plants with DH showed higher root N concentrations. This suggests that N‐supply was not limiting root growth and could indicate that N was possibly allocated from shoots to below‐ground organs or stored in roots for increased production of N‐containing osmolytic compounds (Miller ). In contrast to other studies, where inorganic soil N pools increased during drought (Bloor & Bardgett ; Fuchslueger et al .…”

Toward effective strategies for energy efficient network management

“…As pointed out before, there is not enough knowledge on how to combine both the objective and subjective views in one strategy. [23] points out the risk that not knowing the exact effects of a measure in a complex environment, that is difficult to manage let alone control, likely leads to disproportionate and unintended behavioral changes when the measure is implemented.…”