Ameliorating effect of chitosan and its derivatives on photosynthetic pigments, chlorophyll fluorescence indices, qualitative characteristics and yield of greenhouse tomato (Lycopersicon esculentum Mill.) under deficit irrigation conditions

Recently, the use of biological compounds to ameliorate the effects of environmental stresses on agricultural products has been considered globally. In order to investigate the ameliorating effect of some biological compounds on fluorescence indices, photosynthetic pigments and yield of greenhouse tomatoes under deficit irrigation conditions, the split plot experiment was conducted as a randomized complete block design in the research greenhouse of University of Hormozgan. Experimental factors include irrigation levels (full irrigation as control, moderate and severe deficit irrigation) as the main factor and foliar application of biological compounds as a sub-factor including control (without the use of compounds), proline, chitosan and N-Succinyl and N, O dicarboxymethylate chitosan (NSC and NOC, respectively). Application of biological compounds at each irrigation level increased the amount of chlorophyll a, chlorophyll a to b ratio, carotenoids and SPAD number compared to the control and the highest increase was observed with NSC. The highest values ​​of Fv/Fm in moderate and severe irrigation conditions were obtained with the use of chitosan and NSC, respectively so that this showed an increase of 22.4 and 21.8% in this trait as compared to the control. The highest taste index (1.06) was observed with the use of chitosan in severe deficit irrigated condition by increasing fruit TSS and TA contents. Among the biological compounds, NSC and chitosan had the greatest improving effect on the fruit yield. So that foliar application with NSC increased fruit yield in control, moderate and severe irrigation by 32.5, 91.17 and 24.33%, respectively. Therefore, according to these results, under deficit irrigation conditions, chitosan and its derivatives can reduce the effects of drought stress on tomatoes more efficiently than proline.