The Effects of Biostimulant Application on Growth Parameters of Lettuce Plants Grown under Deficit Irrigation Conditions
The aim of the present study was to examine the potential ameliorative effects of biostimulant application on lettuce plants grown under deficit irrigation conditions. For this purpose,we evaluated the effect of five biostimulant products with varied composition (e.g., seaweed extracts+macronutrients+amino acids (SW); humic+fulvic acids (HF); Si + Ca (SiC); Si (Si); vegetable proteins+amino acids (VP)) and the control treatment (no biostimulant added (NB)) on field grown lettuce plants (Lactuca sativa L.: Romaine type cv. Doris) under deficit irrigation conditions (Control treatment: rain-fed plants; I1: 50% of field capacity; I2: 100% of field capacity). The growth parameters tested were plant weight (aerial part), number of leaves, fresh and dry weight of leaves, plant height, leaf area index (LAI) and specific leaf area (SLA), and SPAD index. Our results indicate that the biostimulant with seaweed extracts+macronutrients+amino acids (SW) combined with deficient irrigation (I1) presented the highest values in terms of plant weight, leaf weight, LAI as well as the chlorophyll content in lettuce plants. According to SPAD values, the biostimulants treatments performed higher values of chlorophyll in the case of rain-fed plants compared to those that were fully irrigated (I2). Also, the Si treatment presented the higher plant height under deficit irrigation (I1) as also the greatest number of leaves. In general, all biostimulants showed a better response to deficit irrigation and to rain-fed plants compared to those with full irrigation in almost all measurements.