Growth, Water Relations, and Ion Content of Field-grown Celery [Apium graveolens L. var. dulce (Mill.) Pers.] under Saline Irrigation

Abstract

We irrigated field-grown celery (Apium graveolens L. var. dulce [Mill.] Pers. ' Tall Utah') with four concentrations of saline water, NSC (nonstressed control), SW1, SW2, and SW3, corresponding to EC of 0.5, 4.4, 8.5, and 15.7 dS·m -1 , respectively, plus a nonirrigated control (NIC) and investigated the effects of the treatments on water relations, yield and ion content. In addition, we compared simultaneously plant response to both salt and drought stress by using a modified version of the threshold-slope model. Increasing salinity of the irrigation water reduced fresh and dry weights of the shoots, but increased the dry matter percentage in shoots. The marketable yield was moderately affected by salinity (25% reduction at EC 8.5 dS·m -1 ). In contrast, a severe water stress dramatically decreased the marketable yield from 23 t·ha -1 (average of the irrigated treatments) to <7 t·ha -1 (nonirrigated control). Na + and Cl - concentrations increased in salinized plants whereas nitrogen content, K + , Ca 2+ , and Mg 2+ concentrations decreased upon salinization. Midday leaf water potentials (Ψ t ) decreased from -1.48 MPa (0.5 dS·m -1 ) to -2.05 MPa (15.7 dS·m -1 ) and - 2.17 MPa (nonirrigated control), though the reduction in leaf cellular turgor was less severe. The maintenance of high leaf cellular turgor was positively correlated to a decrease in osmotic potential and to an increased bulk modulus of elasticity. These results indicate that it is possible to irrigate celery with saline water (up to 8.5 dS·m -1 ) with acceptable losses in marketable yield and confirmed that in the field, this species has the ability to efficiently regulate water and ion homeostasis. In the absence of irrigation, celery plants were unable to cope with the drought stress experienced, although this was comparable, in terms of soil water potential, to the one caused by saline irrigation.