Effects of deficit irrigation applied to home lawns, used as
means of water conservation, are an important issue. However,
the impact of deficit irrigation on sucrose metabolism in tall
fescue (
Festuca arundinacea) is unknown and important because
sucrose is the dominant form of carbohydrate transported to
developing plant organs. The objectives of this study were to
investigate the effects of deficit irrigation on leaf water
content, osmotic potential (
S), sucrose level, and the activity
of sucrose phosphate synthase (SPS; EC 2.4.1.14), sucrose synthase
(SS; EC 2.4.1.13), and acid invertase (AI; EC 3.2.1.26) in tall
fescue leaves. Sods of ‘Falcon II’ tall fescue were
established in polyvinylchloride (PVC) tubes (10 cm diameter
x 40 cm long) filled with a mixture of sand and fritted clay
[9:1 (v:v)] and then placed in growth chambers. Reference evapotranspiration
rate [ETo (millimeters of water per day)] was determined by
weighing the PVC tubes containing well-watered turfgrass every
3 days to determine water loss on a daily basis as ETo. Deficit
irrigation treatments were applied as follows: well-watered
control, mild drought stress (60% ETo), and severe drought stress
(20% ETo). Leaf water content was lower at 6, 12, and 20 days
of treatment for the 20% ETo treatment and 20 days after treatment
began for the 60% ETo treatment. Compared with the well-watered
control,
S was lower in the 60% ETo treatment on all three measurement
dates. Sucrose was higher at 8 and 14 days after treatment began
in the 60% ETo treatment and on all three measurement dates
in the 20% ETo treatment relative to the well-watered control.
No difference in sucrose level was observed between the 20%
ETo and 60% ETo irrigation regimes at 8 and 14 days of treatment.
Beginning 14 days after treatment, tall fescue had a higher
level of SPS in the 60% ETo and 20% ETo treatments compared
with the well-watered treatment. Tall fescue receiving 60% or
20% ETo had a lower level of AI activity on all measurement
dates. Results suggest that the decrease in
S was accompanied
by higher sucrose levels, which were the result of the increased
level of SPS and SS activity and a decline in AI activity.