Effects of deficit irrigation and straw mulching on gas exchange of cucumber plants (Cucumis sativus L.)

Leaves gas exchange were studied in one cucumber (Cucumis sativus L.) cultivar Harriet F1 grown under control conditions (C), deficit irrigation (S) and straw mulch (M), as well as under control or deficit irrigation conditions and straw mulch in combination (CM or SM). Cucumber plants were grown in loose soil, foil tunnel. The photosynthesis rate (PN) and transpiration rate (E) were measured in the leaves in situ using the portable gas exchange system LCpro+. It follows from the results obtained that water deficit (PN was 11.88 μmol CO2.m−2.s−1 and E was 1.83 mmol H2O.m−2.s−1) provably decreases the gas exchange rate in cucumber plants in comparison with the irrigated control group (average value of PN - 15.03 μmol CO2.m−2.s−1 and E – 2.16 mmol H2O.m−2.s−1). The application of mulch in the control and stresses plants statistically insignificantly reduced the photosynthesis rates −14.91 μmol CO2.m−2.s−1 and 11.86 μmol CO2.m−2.s−1, respectively. However, after the application of the mulch to the plants growing in the variant of deficit irrigation and control conditions with mulch, the transpiration rate increased. The rate of transpiration (E) by plants from control and deficit irrigation with mulch was 2.28 mmol H2O.m−2.s−1 and 2.24 mmol H2O.m−2.s−1, respectively. Photosynthesis and transpiration rate is also influenced by stomatal conductance (gs). The obtained values ​of the coefficient of determination (r2) is evident no stomatal inhibition of gas exchange for variants C (r2 = 0.1404 – PN; 0.2352 – E) and CM (r2 = 0.2656 – PN; 0.2483 – E). No stomatal inhibition of photosynthesis was observed in SM variant (r2 = 0.2867), too. However, stomatal inhibition of photosynthesis and transpiration rate was based on the coefficient of determination found in plants with limited irrigation (PN – r2 = 0.5222 and E – r2 = 0.7191) and in SM variant (r2 = 0.8972).