The objective of this study was to determine the effect of 24-epibrassinolide (24-EBL) applications on growth, chlorophyll, and mineral content of lettuce (Lactuca sativa L. var. Crispa) grown under salt stress. The study was conducted in pot experiments under greenhouse conditions. Lettuce seedlings were treated with seed and foliar 24-EBL applications at different concentrations (0, 1, 2, and 3 μM). Salinity treatments were established by adding 0, 50, and 100 mm of sodium chloride (NaCl) to a base complete nutrient solution. Results showed that salt stress negatively affected the growth and mineral content of lettuce plants. However, seed and foliar applications of 24-EBL resulted in greater shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight as well as higher stem diameter than the control under salt stress. Salinity treatments induced significant increases in electrolyte leakage of plant, but foliar 24-EBL application reduced leaf electrolyte leakage and has determined lower values of leaf electrolyte leakage than non-treated ones. In regard to nutrient content, it can be inferred that 24-EBL applications increased almost all nutrient content in leaves and roots of lettuce plants under salt stress. Generally, the greatest values were obtained from 3 μM 24-EBL application. Treatments of 24-EBL alleviated the negative effect of salinity on the growth of lettuce.
Melek Ekinci, Ertan Yildirim, Atilla Dursun and Metin Turan
Ustun Sahin, Melek Ekinci, Fatih Mehmet Kiziloglu, Ertan Yildirim, Metin Turan, Recep Kotan and Selda Ors
The aim of this study was to determine the effects of selected plant growth-promoting rhizobacteria (PGPR) on some physiological characteristics, plant growth, yield, and plant nutrient content of lettuce grown under different irrigation levels. Field experiments were carried out as split plot based on randomized complete block design with three replications. Three irrigation levels, I1 = 100% (control), I2 = 75%, and I3 = 50% of the field capacity (FC), were determined at the 0–15 cm soil depth by time-domain reflectometry (TDR), as main plots and three levels of bacterial species consisting of no bacterial inoculation (control), Bacillus megaterium TV 6D (B1), Bacillus subtilis TV 12H (B2) as sub plots in 2012 and 2013. Physiological characteristics, plant growth, yield, and plant nutrient content of lettuce was significantly affected by PGPR and irrigation quantities. Results showed that decreasing irrigation quantities significantly decreased the growth, dry and fresh head weight, and yield of lettuce in both years. Moreover, lower irrigation levels caused a decrease in leaf relative water content (LRWC), stomatal conductance (SC), and plant nutrient element content, but an increase electrolyte leakage (EL) and lipid peroxidation [malondialdehyde (MDA)]. However, PGPR inoculations significantly increased the growth, nutrient element content, LRWC, SC, and yield but decreased EL and MDA of lettuce plants grown under lower irrigation levels. The results of the study suggested that PGPR inoculations could alleviate the deleterious effects of lower irrigation conditions on the growth and yield of lettuce plants.
Metin Turan, Nizamettin Ataoglu, Adem Gunes, Taskin Oztas, Atilla Dursun, Melek Ekinci, Quirine M. Ketterings and Yuh Ming Huang
Boron (B) deficiency is widespread in the Anatolia region of Turkey. This could impact production and quality of Brussels sprout (Brassica oleracea L. gemmifera). A 2-year field experiment was conducted to study yield and quality response of four cultivars (Star, Brilliant, Oliver, and Maximus) to B addition (0, 1, 3, and 9 kg·ha−1 B). The optimum economic B rate (OEBR) ranged from 5.5 to 6.3 kg·ha−1 B resulting in soil B levels of 0.94 to 1.13 mg·kg−1. Independent of cultivar, B application decreased tissue nitrogen, calcium, and magnesium but increased tissue phosphorus, potassium, iron, manganese, zinc, and copper content. We conclude a B addition of 6 kg·ha−1 is sufficient to elevate soil B levels to nondeficient levels. Similar studies with different soils and initial soil test B levels are needed to conclude if these critical soil test values and OEBR can be applied across the region.