Abstract
Sweet kernel apricot (Prunus armeniaca×sibirica) is a Chinese characteristic species and an
important ecological, woody grain and oil tree in the “Sanbei” area, but the biomass accumulation
and photosynthetic responses of sweet kernel apricot seedlings to soil drought stress are unclear.
Samples of the P. armeniaca×sibirica cultivar, Zhongren No. 1 were collected, and 6 water content
gradients were arranged in the ancient course of the middle Yellow River: 14.0 (±0.5%), 12.0
(±0.5%), 10.0 (±0.5%), 8.0 (±0.5%), 6.0 (±0.5%) and 4.0% (±0.5%). Results showed that (1)
the leaf’s net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) initially
increased and then gradually decreased as the water content decreased, while there was an increasing
then declining tendency in water use efficiency (WUE). (2) The diurnal variation curve was a
unimodal type for Zhongren No. 1 which had no midday depression of photosynthesis. When the
soil water decreased, the light saturation point (LSP) gradually declined and the light compensation
point (LCP) increased. (3) When the soil water content declined, the photosynthsis system PS
II original light energy conversion efficiency (Fv /Fm), the maximum fluorescence (Fm), apparent
photosynthetic electron transport rate (ETR) and coefficient of photochemical quenching (qP) all
decreased while there was a little increment of 12.0% in the F0, and the coefficient of photochemical
quenching (qN) initially increased and then declined. (4) As the soil water decreased, the biomass
accumulation gradually dropped while the root-shoot ratio increased. The damage from water
deficits was regulated through an increment in the root-shoot ratio. Our results suggested that on
8.0~14.0% soil water content would be suitable, and on optimum moisture content was 12.0%.
Meanwhile, the minimum moisture content in the soil to keep P. armeniaca×sibirica cultivar
Zhongren No. 1 seedlings alive would be no less than 4.0%.