Methodological and physiological study of seed dormancy release in Tilia henryana

Tilia henryana is a rare tree of the Tilia family, found exclusively in China. Its seeds have severe dormancy features that limit its normal conditions of reproduction and renewal. Its seeds have severe dormant characteristics that limit its normal conditions of reproduction and renewal. The Dormancy in T. henryana seeds is a comprehensive dormancy (PY + PD) caused by mechanical and permeability barriers of seed coat and the presence of germination inhibitor in endosperm. L₉ (3⁴) orthogonal test was used to determine the best procedure for releasing the dormancy of T. henryana seeds, that is, first treating the seeds with H₂SO₄ for 15 min, followed by the application of 1 g L^-1 GA₃, stratification at 5 °C for 45 days, and finally germination at 20 °C, which can achieve a 98% seed germination rate. Large amounts of fat are consumed throughout the dormancy release process. As quantities of protein and starch marginally increase, soluble sugars are continuously decreased. Acid phosphatase and amylase activities increased rapidly, and the combined enzyme activities of G-6-PDH and 6-PGDH related to the PPP were also significantly increased. The levels of GA and ZR continued to increase, while the levels of ABA and IAA gradually decreased, among which GA and ABA changed most rapidly. The total amino acids content continued to decrease. Asp, Cys, Leu, Phe, His, Lys and Arg decreased with dormancy release, while Ser, Glu, Ala, Ile, Pro and Gaba showed an upward trend. The physical dormancy of T. henryana seeds is broken with H₂SO₄ in order to make the seed coat more permeable, which is a prerequisite for germination. As a result, the seeds can absorb water and engage in physiological metabolic activities, particularly the hydrolysis and metabolism of fat, which supply a significant amount of energy for dormancy release. In addition, rapid variations in the levels of different endogenous hormones and free amino acids, induced by cold stratification and GA₃ application, are another important factor promoting the quick physiological activation of seeds and breaking the endosperm barrier.