Influence of humic acid on germination, morphological characteristics and photosynthesis pigments of Trifolium alexandrium L. under salinity stress

The study was done to determine the effect of humic acid on germination, morphological properties and photosynthesis pigments of Trifolium alexandrium L. under salt stress.

This study was conducted in a factorial experiment in a completely randomized design (using analysis of variance). The first factor was humic acid (0,0.009mgLi−1). The second factor was salt stress (0,0.75,1.5,3dSm−1). Seed germination, vigor index, allometric coefficient, radicle and pedicle length, total dry and fresh weight, and photosynthetic contents were measured.

The minimum and maximum germination rate (4.00 and 4.90seed/day) and vigor index (1.79 and 6.33) were related to 3dSm-1 and H+3dSm-1 treatments, respectively. The germination percentage did not show significant difference (p<0.05). The radicle and pedicle lengths, allometric coefficient, germination rate and vigor index in the zero treatment were more than the H treatment but they decreased with increasing salinity. The minimum and maximum radicle (0.79 and 2.30cm), pedicle lengths (0.79 and 2.55cm) and dry weight (0.0014 and 0.0026g) were related to the 3dSm-1 and H+3dSm-1 treatments, respectively. The highest chlorophyll a (0.31 mg g-1 fresh weight), carotenoid (0.07 mg g-1 fresh weight) and total chlorophyll (0.48mgg-1 fresh weight) were related to H+1.5dSm-1. The highest amount of chlorophyll b (0.34mg g-1 fresh weight) was observed in H+3dSm-1.

Humic acid had different but positive effects on quantitative properties and germination characteristics of the plant in salinity stress. The use of this fertilizer in salinity stress for salinity-sensitive plants can be useful but more comprehensive survey in the field is recommended.