PJB-2017-306
Effect of humic acid on seed germination of sub-tropical halophytes under salt stress
Sonia Bano Abbasi, Bilquees Gul, Nasiruddin Khan, Salman Gulzar and Muhammad Zaheer Ahmed
Abstract
This study was carried out to determine the effects of exogenous applications of three humic acid types (HA1, HA2, HA3) and their concentrations (250 and 500 mg L-1) on seed germination of ten halophytes. The species included Aeluropus lagopoides, Arthrocnemum macrostachyum, Cyperus conglomeratus, Desmostachya bipinnata, Halocnemum strobilaceum, Halopeplis perfoliata, Halopyrum mucronatum, Phragmites karka, Sporobolus ioclados and Urochondra setulosa whereas, treatments used were (1) thermoperiod (10/20 and 20/30oC); (2) photoperiod (12/12h, light/dark; and 24h dark) under non-saline conditions. Effects of humic acids on alleviation of seed germination were also studied in response to 1) the individual and combined effects of NaCl treatments (reported to cause 50% germination inhibition in species tested) and 2) photoperiod (12/12h, light/dark; and 24h dark). In non-saline conditions, humic acid did not alleviate seed germination under the sub-optimal thermoperiod (10/20oC) in most halophyte seeds studied except for that of HA1 in A. lagopoides (34%), A. macrostachyum (15%), D. bipinnata (12%) and H. perfoliata (20%). Humic acid did not improve seed germination in either photoperiod under non-saline conditions at the optimal thermoperiod (20/30oC). In the presence of the light (12/12h; light/dark photoperiod), humic acid alleviated seed germination of U. setulosa under saline conditions but not in any of the other test species. Under saline condition and complete darkness, the lower concentration treatment (250 mg L-1) of all three humic acid types significantly improved seed germination of A. lagopoides, C. conglomeratus, D. bipinnata, H. perfoliata, P. karka and U. setulosa. Under saline conditions and absence of light, higher concentration (at 500 mg L-1) of all humic acid types alleviated seed germination in S. ioclados however, no effect of either humic acid type was observed on seed germination of H. strobilaceum. In conclusion, HA could partially substitute the light requirement for seed germination of test species under saline conditions
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