EFFECTS OF DRIP IRRIGATION MODE AND NaCl CONCENTRATION ON GROWTH AND HYDRAULIC CONDUCTANCE OF APPLE SEEDLINGS
YANG Qi-Liang, ZHANG Fu-Cang, LIU Xiao-Gang, YANG Zhen-Yu
Chin J Plan Ecolo. 2009, 33 (4):
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Aims Hydraulic conductance, which is characterized by root water uptake and xylem water transport efficiency, is a physiological response of plants to different environmental factors, such as salt-stress and water deficit. However, there is little research on relationships between different drip irrigation modes and hydraulic conductance. Our objectives were to determine 1) the impact on growth and hydraulic conductance of different drip irrigation modes and salinity treatments and 2) the relationship between apple seedling growth and hydraulic conductance.
Methods The experiment used a NaCl concentration gradient of 0 (CK), 0.2% (S1), 0.3% (S2) and 0.4% (S3) and three drip irrigation modes: alternate partial root zone drip irrigation (ADI, alternate watering on both sides of the root zone), fixed partial root zone drip irrigation (FDI, fixed watering on one side of the root zone) and conventional drip irrigation (CDI, simultaneous watering on both sides of the root-zone).
Important findings Drip irrigation modes and NaCl concentration significantly affect apple seedling growth and hydraulic conductance. Dry matter, leaf area, net growth and hydraulic conductance of apple seedlings were significantly inversely related to NaCl concentration under the same drip irrigation treatment. Root hydraulic conductance (Kr) was significantly linearly correlated with total root dry weight, shoot hydraulic conductance (Ksh) and shoot dry weight. Under the same NaCl concentration treatment and compared with CDI, ADI had a water savings of up to 50%, but average root dry weight, shoot dry weight, total dry weight, leaf area, plant net growth and root hydraulic conductance of ADI only decreased by 8.7%, 19.24%, 13.47%, 11.87%, 32.96% and 10.72%, respectively, showing that ADI has an obvious promoting effect on apple seedling growth and hydraulic conductance. Compared with CDI, high NaCl concentrations S2 and S3 led to decreases in Kl+p of ADI of 33.56% and 44.26%, respectively, while the Kr of ADI treatment increased by 1.13% and 10.91%, respectively, indicating that the root hydraulic signal transmission efficiency of ADI treated seedlings, the ability of seedlings to regulate water balance and resistance stability to salt-stress could be enhanced. The growth and hydraulic conductance of ADI were all higher than FDI. Use of ADI not only improved water-saving regulation ability, but also strengthened resistance stability to salt-stress.