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Physiological Response of Meadowfoam to Crop Water Deficits

Pearson, C. H., Jolliff, G. D.
Agronomy journal 1985 v.77 no.3 pp. 422-426
transpiration, water stress, oil crops, Limnanthes alba, Oregon
Meadowfoam (Limnanthes alba Benth.), a new oilseed crop, is adapted to wet meadows in its native habitat. The effect of plant water stress during seed development has not been reported, but was postulated as a cause of seed yield variation in cultivated fields. The objective of this field study was to characterize meadowfoam response to water stress. Treatments included: No irrigation (control); early irrigation, during May (El); and continued irrigation, from the 1st week of May until crop maturity (CT). They were applied in a randomized complete block experimental design on a Woodburn silt loam soil (flne-silty, mixed mesic Aquultic Argixerolls) in 1981 and 1982. Plant water potential Ψ, turgor potential (Ψₚ), osmotic potential (Ψπ), stomatal resistance (R), transpiration (Tr), and canopy temperature (CT) were measured at 0600, 0900, 1200, 1500, and 1800 h on several days during flowering and seed development. Differences between treatments for Ψ, Ψₚ, Ψπ R, Tr, and CT were not apparent in 1981, probably because above average precipitation occurred during May and June keeping all treatments moist. However, these data were useful to characterize physiological responses of meadowfoam due to changes in plant age and environmental conditions during a season when soil water deficits were not severe. Generally, crop water deficits were greatest and Tr was highest at 1500 h, and R was highest at 1800 h. In contrast to many other crop species, meadowfoam maintained an unusually high Ψ which did not drop below −0.8 MPa. The amount of precipitation during flowering in 1982 was the lowest in 16 years. At mid-flowering after 1200 h the control plants had higher crop water deficits, higher R, lower Tr, and slightly higher CT than the irrigated plants. These responses became progressively greater by late flowering and early seed fill. Crop water stress in the El treatment was slight at mid-and late flowering, but became greater at early seed fill. During a typical day Ψₚ decreased in response to lower Ψ with less than 0.2 MPa decrease in Ψπ. The control had an Ψπ that was only 0.07 MPa lower than the irrigated treatments. Adaptation of meadowfoam to crop water stress by lowering Ψπ was minimal. Stomatal closure occurred between a Ψ of −0.5 to −0.7 MPa. The CT of the control at mid-flowering, late flowering, and early seed fill averaged 0.4, 1.0, and 2.3 °C higher than the CI treatment, respectively. Canopy temperatures of the El treatment at early seed fill averaged 0.8°C higher than the CI treatment. The results indicated that meadowfoam requires a high Ψ for growth and development, and its tolerance to crop water deficits is low.