© 1997 Heron Publishing—Victoria, Canada
Influence of irradiance on water relations and carbon flux during rooting of Shorea leprosula leafy stem cuttings
H. Aminah (1), J. McP. Dick (2) and J. Grace (3)
1. Forest Research Institute Malaysia (FRIM), Kepong, 52109 Kuala Lumpur, Malaysia / 2. Institute of Terrestrial Ecology, Bush Estate, Penicuik EH26 0QB, U.K. / 3. Institute of Ecology and Resource Management, University of Edinburgh, Darwin Building, Mayfield Road, Edinburgh EH9 3JU,
U.K. / Received May 26, 1995
Summary
Single-node leafy stem cuttings of Shorea leprosula Miq. were subjected to a high, intermediate or low irradiance treatment for 16 weeks in an enclosed mist propagation system.
Before rooting, maximum photosynthesis of the cuttings occurred at an irradiance of 400 µmol m–2 s–1. Although none of the irradiance treatments affected the number of roots produced per cutting, the numbers of cuttings that
formed roots were 50 and 30% in the high irradiance (diurnal range of 0–658 µmol m–2 s–1) and low irradiance (diurnal range of 0–98 µmol m–2 s–1) treatments, respectively, compared with 62% in the intermediate irradiance treatment (diurnal range of 0–360 µmol m–2 s–1). Low rooting frequency of cuttings in the high irradiance treatment was associated with water deficits (maximum leaf-to-air
vapor pressure deficit (VPD) = 3.6 kPa), whereas cuttings in the low irradiance treatment had a low rooting frequency because
they were below the light compensation point most of the time. In the intermediate irradiance treatment, cuttings withstood
a daily maximum VPD of 1–2 kPa and recovered overnight from the previous day’s deficit, as indicated by higher relative water
content (RWC) and stomatal conductance (gs) in the morning than in the previous afternoon and evening. Higher RWC and gs of cuttings in all treatments on Days 14 and 21 compared with Day 8 probably indicated recovery from water deficit following
severance and insertion of the cuttings in rooting medium. There were negative relationships between stem volume of cuttings
and both number of cuttings that rooted and number of roots per cutting.
Keywords:
leaf-to-air vapor pressure deficit, photosynthesis, relative water content, stomatal conductance, vegetative propagation.
