Coastal Almond-Leaved Pear (Pyrus spinosa) Seedlings’ Responses to Saline Stress Alleviated by Formulated L-Methionine and Bacterial Exogenous Soil Application

Coastal Pyrus spinosa seedlings were tested for their developmental, chlorophyll content and antioxidant performance under soil saline conditions where bacterial and l-methionine exogenous treatments were applied as potential saline alleviation stress schemes. Scaling up saline stress, the number of formed lateral shoots was reduced in all treatments. Medium salt stress (75 mM NaCl) demonstrated a rather unified decline in shoot fresh weight values, which became toxic at 100 mM NaCl, with up to 89.1% shoot fresh weight losses, in comparison to unchallenged status. Both exogenous applications increased root/shoot ratio, providing developmental boost for root growth. Total chlorophyll content values (May–July) did not differ among non-stressed plantlets independently of exogenous treatment. All experimental plantlet lines increased their antioxidant activity on scaled up soil NaCl enrichment. Νo differences in root orientation and their angle frequencies were observed while soil saline exposure took place. In brief, spring–summer exposure of P. spinosa plantlets under 100 mM NaCl saline stress can be manageable, achieving higher root/shoot ratio values, upregulating leaf antioxidant activity and optimizing root growth upon bacterial and l-methionine supplementation. However, many of the examined parameters were found to be not extensively different between exogenously treated plantlets and non-supplemented ones, suggesting a potential role of intergenerational and transgenerational stress memory.