NO signaling is a key component of the root growth response to nitrate inZea maysL.

Abstract

To search for nutrients and water, roots need to efficiently explore large soil volumes. To this aim they generate complex root systems, allowing them to maximize their resource allocation efficiency. 1 Despite the vital importance of roots, the difficulty in accessing intact root systems for analysis, particularly under field conditions, have slowed down the breeding programs for plant's adaptation to environmental restrictions. 2,3 The capacity of plants to take up nutrients and water is mainly determined by changes in the architecture of the root system. 1 Three major processes affect the overall architecture of the root system: the rate of cell division, the rate of cell differentiation, and the extent of expansion and elongation of cells. [4][5][6] Disturbs in any of these 3 processes can affect the whole root-system architecture and the capacity of plants to survive and develop in adverse environments (Giehl et al. 7 and references therein).The root system results from the coordinated control of both genetic endogenous programs (regulating growth and organogenesis) and the action of abiotic and biotic environmental stimuli. 8,9 The dynamic control of the overall root system architecture (RSA) throughout time finally determines root plasticity and allows plants to efficiently adapt to environmental constraints. 10 The soil-environment from which plants extract nutrients and water is extremely heterogeneous, both spatially and temporally. 11 Among the nutrients present in soil, nitrate (NO 3 − ) may vary by an order of magnitude within centimeters or over the course of a day. 12 The effects of NO 3 − on the root system are complex and depend on several factors, such as the concentration available to the plant, the endogenous nitrogen status and the sensitivity of the species. 10,13,14 A considerable part of the studies aimed to unravel the mechanisms controlling RSA growth and development in response to nitrate have been focused on lateral roots (LR), 8,13,[15][16][17][18][19][20] while the nitrate-regulation of the primary root growth is still unclear. Beside NO 3 − , auxin has been demonstrated to strongly affect and control the LR development, [21][22][23][24] and an increasing number of studies suggests an overlap between auxin and NO 3 − signaling pathways in controlling LR development. [25][26][27][28][29][30][31][32][33] NO 3 -has a Doubtful Role in Regulating the Growth of Primary RootsDespite the high amount of reports published on nitrate effects on root elongation, the lack of univocal results makes it difficult to clearly decipher this response ( Table 1). In Arabidopsis thaliana, inhibition of primary root growth has been observed when nitrate is applied homogeneously at high concentrations (50 mM) for 7 d, but not in a range between 0.1 and 10 mM. 35 On the contrary, in this same species Linkohr et al. 36 showed an inhibition of primary root elongation with the increase of nitrate concentration already beyond 0.01 mM, but in this case seedlings were IAA, indole-3-acetic acid; SNP, sodium n...

Humic Acid-Induced Hairy Root Growth in Basil Ismodulated by Nitric Oxide and Reactive Oxygen Species

“…Considering what was discussed above, and accepting the role of NO on root growth promotion [11] [12] [13], the present results indicate that HA addition promoted an increase in NO levels. This process was analyzed by fluorescence microscopy ( Figure 4 and Figure 5), and similar responses to those previously observed for the addition of auxin were found [14].…”

“…The increased emission of absorbent hairs and lateral roots in response to HA is usually related to interactions among HA, auxin, and nitric oxide (NO) [9] [10] [11]. Nitric oxide plays a central role in the determination of the root morphology and developmental pattern [11] [12] [13].…”

“…Nitric oxide plays a central role in the determination of the root morphology and developmental pattern [11] [12] [13]. [14] used an NO scavenger to prevent the formation of lateral and adventitious roots and root gravitropic response, indicating an important role of endogenous NO in mediating these processes.…”

Nitrate: A Crucial Signal during Lateral Roots Development

“…Apart from the above-mentioned pathways including transcription factors and hormonal signals, more recently, nitric oxide (NO) has been reported to be a key nitrate-related signal to regulate the root system architecture in plants (Chen et al, 2010; Meng et al, 2012; Trevisan et al, 2014). In rice, NO generated by the nitrate reductase (NR) could improve the N acquisition capacity by increasing LR initiation under partial nitrate nutrition (Sun et al, 2015).…”

Strigolactones are required for nitric oxide to induce root elongation in response to nitrogen and phosphate deficiencies in rice

“…; Trevisan et al . ). For example, higher endogenous NO in N‐deficient roots was similar to the enhancement of primary root lengths in maize (Zhao et al .…”