Responses of hypocotyl growth and seedling emergence with respect to soil sowing depth stress in peanut (Arachis hypogaea L.)

Abstract

ABSTRACT Optimal sowing depth plays an important role in peanut’s stand establishment and yield. A field experiment was conducted to investigate sowing depths effects (3 cm, SD3; 5 cm, SD5; 7 cm, SD7; 9 cm, SD9; 11 cm, SD11; 13 cm, SD13; 15 cm, SD15) on soil environments, hypocotyl growth, endogenous hormones content, and pod yield. Both shallow- (3 cm) and deep-sowing (15 cm) treatments decreased the pod yield due to plant and pod number lowering that resulted from decreased seedling emergence rate (SER). SD3 treatment possessed less soil water content (SWC) that led to lowered SER. Soil penetration resistance (SPR) was significantly increased with sowing depths that resulted in SER decrease and delayed emergence time. Compared with the SD5 treatment, the SER was 15.7% and 16.6% lower in SD15 treatment in the 2017 and 2018 season, respectively. SD5 and SD15 took 111.1 and 161.5 day-degrees (°Cd), respectively; to attain maximum length. Further, sowing depth increase resulted in elevated cotyledon’s lipase activities, endogenous auxin (IAA) and gibberellin (GA3) contents, and hypocotyl dry weight. However, decreased cotyledon weight implied that hypocotyl growth of deep-sowing exhausted the stored nutrition by increasing endogenous GA3 and IAA, to sustain its emergence above the soil.