PHYSIOLOGICAL RESPONSES OF ONION (ALLIUM CEPA L.) SEEDLINGS EXPOSED TO DROUGHT

Twenty-one day old onion seedlings were subjected to various drought regimes by withholding water.
Soil moisture potential (ext), leaf water potential (L), growth, photosynthesis (Pn), stomatal conductance (Cs), leaf transpiration (Tl), water use efficiency (WUE), membrane function, nature and accumulation of quaternary ammonium compounds (QAC) were all investigated.
Withholding water for 25 days reduced soil water potential to –1.23 MPa.
While withholding water for various time periods caused ext to decline, there was no parallel reduction in L. Leaf area expansion, Cs, Tl and membrane integrity, as measured by tissue capacitance, and membrane injury index, all reduced significantly as ext declined.
Pn increased despite root zone water potential decline.
An increase in Pn and a decline in Tl resulted in maintenance of WUE in plants under drought.
Glycinebetaine, a quaternary ammonium compound, was identified but it did not accumulate in response to water deficit.
A threshold for the decline in growth, Cs, Tl and membrane integrity was –0.43 MPa.
Onion seedlings appear to tolerate drought through increasing WUE.

XXVI International Horticultural Congress: Environmental Stress and Horticulture Crops

T.J. Caldwell, R. Lada, D. Hooper

Allium cepa, drought, glycinebetaine, water deficit, stress response, quaternary ammonium compounds, water use efficiency

https://doi.org/10.17660/ActaHortic.2003.618.37