Physiological Responses of Onion Varieties to varying Photoperiod and Temperature Regimes

Oli G. Bachie, Louis S. Santiago and Milton E. McGiffen
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Oli G. Bachie: University of California, Agriculture and Natural Resources, Holtville, CA 92250, USA
Louis S. Santiago: Department of Botany and Plant Science, University of California, Riverside, CA 92521, USA
Milton E. McGiffen: Department of Botany and Plant Science, University of California, Riverside, CA 92521, USA

Agriculture, 2019, vol. 9, issue 10, 1-8

Abstract: We measured the gas exchange parameters of six onion varieties in two photoperiodic regimes. The photoperiods simulated early (long-day) and late (short-day) onion growing seasons of the high desert regions near Lancaster, California. We used six locally grown onion varieties: RedBull (RB), RedWing (RW), Hybrid Cometa (HC), Granero (YG), Hybrid Valero (HV) and Hybrid SR (HS). For both photoperiod regimes, daylength and temperature were changed weekly to represent the natural progression of field growing conditions. The results show that the onion plants grown under short-daylength (SD) and higher temperature regimes exhibited higher leaf photosynthetic rates and stomatal conductance than onion seedlings grown under the long-day (LD) regime. Onion plants also had different functional leaf traits depending on crop growth environment during the onset of bulbing. The higher photosynthetic rate of the short-day plants coincided with bulb initiation. Onion photosynthesis and stomatal conductance increased at bulb initiation, apparently to provide carbohydrates for growth and storage in the bulb.

Keywords: onion; photoperiod; daylength; growth chambers; photosynthetic rate; bulb formation (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2019
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