Effects of different pH and cadmium concentrations on physiology of seed germination and seedling growth of cigar

【Objective】This paper explored the effect of different pH and cadmium(Cd) concentrations on physiology of seed germination and seedling growth of cigar, in order to provide reference for obtaining high-quality and safe cigar raw material.【Method】Hydroponics experiment was carried out and different pH(3, 5, 7, 9 and 11) and Cd concentrations(0, 10, 50 and 250 µmol/L) were set. The seed germination indexes(germination rate and germination energy), seedling growth physiological indexesradicle length, embryo length, dry matter weight, chlorophyll content, nitrate reductase activity, malondialdehyde(MDA) content, root activityand Cd content in various parts of seedlings were measured.【Result】Under the same Cd concentration, the germination rate of cigar seeds first increased and then decreased with the increase of pH. Under the same pH, the germination rate of cigar seeds treated with Cd decreased gradually with the increase of Cd concentration. The germination energy and germination rate of seeds were the highest when pH was 7and the Cd concentration was 10 µmol/L. Under the same pH, the radicle length of cigar seedlings first increased and then decreased with the increase of Cd concentration. The embryo length of seedlings decreased with the increase of Cd concentration when pH was 3 and 7. Under other pH conditions, the embryo length of seedlings increased at first and then decreased with the increase of Cd concentration. The radicle length and embryo length reached the longest when pH was 9and Cd concentration was 10 umol/L. Except for the treatment of 0 µmol/L Cd, the dry matter weight of cigar seedlings decreased with the increase of Cd concentration, and increased at first and then decreased with the increase of pH. Under the treatment of 10-250 µmol/L Cd, the Cd content in roots, stems and leaves of cigar seedlings decreased gradually with the increase of pH, and increased with the increase of Cd concentration. The chlorophyll content, nitrate reductase activity and root activity of cigar seedlings increased at first and then decreased with the increase of pH, but it decreased with the increase of Cd concentration. The content of MDA in cigar seedlings increased with the increase of Cd concentration when pH was 5-11. Under the treatment of 10-250 µmol/L Cd, the content of MDA increased at first, then decreased and then increased with the increase of pH, and reached the minimum when pH was 7.【Conclusion】Low Cd concentration promotes the germination of cigar seeds, but the growth physiology of cigar seedlings is inhibited with the increase of Cd concentration. The change of pH will affect the absorption and accumulation of heavy metal Cd by cigar seedlings, and then affect the normal growth and dry matter accumulation of cigar seedlings. When pH is 7, 10 µmol/L Cd treatment increases the chlorophyll content, nitrate reductase activity and root activity of cigar seedlings, being beneficial to the growth of cigar seedlings.