Effects of hormone seed soaking on the early growth of Pistacia chinensis and the drought resistance of its seedlings

This study aimed to investigate the effects of hormone soaking treatments on seedling emergence of Pistacia chinensis seeds and the drought resistance of the resulting seedlings, to provide a theoretical basis for the development of the Pistacia chinensis seed industry and its high-quality cultivation.

Seeds were treated with different hormone solutions. The effects on early growth were assessed by measuring emergence rate and morphological parameters. Subsequently, seedlings were subjected to three drought treatments: control (W1, 60%-70% soil relative water content), mild drought stress (W2, 40%-50%), and severe drought stress (W3, 20%-30%). Morphological and physiological indicators of seedlings from different hormone treatments under drought conditions were examined. Drought resistance was comprehensively evaluated using the drought damage index, principal component analysis, and membership function analysis.

1) All three hormones significantly improved the emergence rate of Pistacia chinensis seeds, with gibberellin (GA₃) being the most effective. GA₃ also promoted the growth of seedling height and ground diameter; 2) As drought stress intensified, the growth of seedling height, ground diameter, and roots was increasingly inhibited, with the extent of inhibition varying among hormone treatments; 3) With progressive stress, leaf relative water content decreased, while relative electrical conductivity and proline content increased. Malondialdehyde content initially increased and then declined. The responses of chlorophyll content, soluble sugar content, soluble protein content, and superoxide dismutase activity to drought stress varied depending on the hormone soaking treatment; 4) The drought resistance of seedlings from different hormone treatments, in descending order, was as follows: indole-3-butyric acid (IBA) > naphthaleneacetic acid (NAA) > water control > GA₃.

Soaking treatments with 500 mg/L IBA, GA₃, and NAA all significantly enhanced the emergence rate of Pistacia chinensis seeds. GA₃ promoted seedling growth, whereas IBA improved drought resistance in seedlings.