Root Growth of Avocado is More Sensitive to Salinity than Shoot Growth

Abstract

<jats:p>In most crop species, growth of the shoot is more sensitive to salt stress than root growth. Avocado [<jats:italic>Persea americana</jats:italic> Mill.] is very sensitive to NaCl stress. Even low concentrations of salt (15 m<jats:sc>m</jats:sc>) inhibit tree growth and decrease productivity. Observations in experimental orchards have suggested that root growth in avocado might be more restricted by salinity than shoot growth. In the present study, we evaluated quantitatively the inhibitory effects of salt stress on growth of the avocado root in comparison to the shoot. Seedling plants of the West-Indian rootstock `Degania 117' were grown in complete nutrient solution containing 1, 5, 15, or 25 m<jats:sc>m</jats:sc> NaCl. The threshold NaCl concentration causing root and shoot growth reduction occurred between 5 and 15 m<jats:sc>m</jats:sc>. At all concentrations, root growth was much more sensitive to salinity than shoot growth. A concentration of 15 m<jats:sc>m</jats:sc> NaCl, which did not affect the rate of leaf emergence on the plant and decreased leaf biomass production only 10%, induced a 43% reduction in the rate of root elongation and decreased root volumetric growth rate by 33%. Under 25 m<jats:sc>m</jats:sc> NaCl, leaf biomass production, leaf initiation rate and leaf elongation rate were reduced 19.5%, 12%, and 5%, respectively, while root volumetric growth and root elongation rate were reduced 65% and 75%, respectively. This strong root growth inhibition is expected to influence the whole plant and therefore root growth under salinity should be considered as an important criterion for rootstocks' tolerance to NaCl.</jats:p>

Evaluation of Alfalfa (Medicago sativa L.) Populations’ Response to Salinity Stress

“…In studies with other crops, researchers have also observed decreased shoot-root ratios with increasing salinity (Pearen et al, 1997;Bayuelo-Jiménez et al, 2003;Acosta-Motos et al, 2015). However, there are some reports of increased shoot-root ratios (Bernstein et al, 2004;AbdElgawad et al, 2016). The observation that salinity has less of an adverse effect on root growth compared with shoot growth is consistent with other observations related to stress, such as P deficiency (Fredeen et al, 1989), N deficiency (Sattelmacher et al, 1990), and drought stress (Sharp et al, 1988;Buwalda and Lenz, 1992).…”

“…However, shoot growth has been found to be more adversely affected by salinity than root growth (Munns and Termaat, 1986). However, there are some reports of increased shoot-root ratios (Bernstein et al, 2004;AbdElgawad et al, 2016). The root biomass per plant was reduced by 18 and 49%, respectively, while the shoot biomass was reduced by 50 and 73%, respectively.…”

Changes in root growth and relationships between plant organs and root hydraulic traits in American elm (Ulmus americana L.) and red oak (Quercus rubra L.) seedlings due to elevated CO2 level

“…These results are in contrast to results of plants grown in saline soil (Katsuhara et al, 2003;Bernstein et al, 2004), indicating that different changing environments result in different responses of plants. Table 2 shows that changes in hydraulic traits are associated with changes in plant organ biomass and morphology in both species, which likely suggest that plant organ development gradually alters hydraulic traits.…”

“…On the other hand, hydraulic traits of roots can also affect plant organ growth and development. When a plant grows in saline soil, the hydraulic conductance of roots is very low (Katsuhara et al, 2003;Bernstein et al, 2004). This low conductance restrains the growth and development of plant organs (roots, leaves, stems) as well as that of the entire plant (Katsuhara et al, 2003;Mencuccini, 2003;Bernstein et al, 2004).…”

Effects of Salinity on the Growth and Development of Groundnut PlANT (Arachis hypogaea L.)

“…Shoot height and the number of survived plants decreased with the increase of salt concentrations. Decreased growth under salt stress has been reported on arocado plant species (Bernstein et al, 2004). At 12 days, the highest shoot height (19.51± 0.96) was found at 50 mM salt concentration while at 22, 32 and 42 days it was highest in control.…”