Effect of photoperiod and temperature on garlic (Allium sativum L.) bulbing and selected endogenous chemical factors

Photoperiod and temperature are important environmental factors that regulate many developmental processes in plants. However, the roles of different durations of photoperiod and temperature in garlic bulbing and selected endogenous chemical factors are still unknown. This study is focused on morphological and selected endogenous chemical factors associated with garlic bulb formation in response to photoperiod and temperature. Endogenous phytohormones, phenolic acids and allicin level were analyzed in garlic when plants were subjected to different combinations of photoperiod (light/dark: 10/14 h, 12/12 h, 14/10 h) and temperature (light/dark: 25/18 °C, 30/20 °C) treatments at 10, 20 and 30 days after treatment (DAT). Garlic plant and bulb morphology was observed maximum under 14 h photoperiod and 30 °C at 30 DAT. 14 h photoperiod and 25 °C resulted in maximum ABA, ZT and ZR at 20, 30 and 10 DAT, respectively. Maximum GA and JA were observed under14 h photoperiod and 30 °C at 20 and 10 DAT, respectively. Whereas maximum IAA was detected under 12 h photoperiod and 30 °C at 30 DAT. Maximum ferulic and vanillic acids were detected under 14 h photoperiod and 25 °C at 20 and 30 DAT, respectively. Maximum caffeic, p-coumaric and p-hydroxybenzoic acids were detected under14 h photoperiod and 30 °C at 30 and 10 DAT, respectively. Maximum allicin content was observed under 14 h photoperiod and 25 °C at 30 DAT. Our results propose that endogenous phytohormones, phenolic acids and allicin in pseudostem might control bulbing in garlic.