The role of slab water content during supplemental lighting on shoot growth and physiological response of cut rose ‘Charming Black’

Abstract

The critical water content in slab, and effects of drought on shoot growth and gas exchange characteristics of the cut rose ‘Charming Black’ were investigated. Four different irrigation regimes were applied to rose plants during supplemental lighting (90 µmol m−2 s−1 PAR). Water content in slab was controlled as 80%, 60%, 40%, and 20% in T1, T2, T3, and T4, respectively. No significant difference between T1 and T2 was found when water content in slab was above 60%. However, reduction in water use efficiency has been observed with the decline of water content in slab. When the water content dropped below 60% in slab, the shoot growth rate decreased, and a significant reduction of 30% and 38% in shoot growth, 44% and 51% in shoot weight, and 34% and 56% in leaf area have been observed under T3 and T4 respectively. Also, petal length and diameter of floral buds were hampered due to the water deficit. Lowest net CO2 assimilation rate occurred at the lowest water content in slab (20%). Besides, T3 (40%) also caused a significant reduction (63%) in photosynthesis. Sigmoid function was simulated to find the fraction of total available water that crop can extract from root zone without suffering from drought stress: the fraction is 0.42. Meanwhile, critical water content was calculated as 46.6%. This study showed that when the water content in slab was below the critical water content, drought stress occurred.