Effects of water and nitrogen supply on growth, water-use efficiency and mucilage yield of isabgol (Plantago ovata Forsk)

A two-way factorial experiment based on a randomized complete design (RCD) with four replications was used to compare four levels of N supply including control (N0), 60(N60), 120(N120) and 180(N180) mg N per Kg soil and four different water supply including 100(I100), 80(I80), 60(I60) and 40(I40) % FC on growth, water-use efficiency and mucilage yield of isabgol. Under I40, higher N addition led to a significant decrease in root and shoot DM. N addition increased root and shoot biomass especially in I80 treatment followed by I60. The highest (1.71 g plant-1) and the lowest (0.42 g plant-1) seed yield of isabgol observed in I100 at N120 and I40 at N120, respectively. The concentration of soluble sugar increased with N supply at I100 and I40. Water stress led to an increase in proline levels, particularly in the N supply treatments. The addition of N tended to reduce the positive effect of water stress on proline content. Seed water use efficiency (WUEg) of isabgol decreased with the increase in drought stress. N supply significantly increased WUEg from N0 to N120 with no significant differences between N60 and N120 and then significantly decreased by supplying N180. Mucillage water use efficiency (WUEm) is also increased linear in all watering regime at all N supply.