Photosynthetic, evapotranspiratory and leaf morphological properties of chrysanthemum grown under root restriction as affected by fertigation frequency

This experiment was conducted to clarify the effect of fertigation frequency (once or 8 times per day) on the growth, evapotranspiration rate, and photosynthetic and leaf morphological properties of chrysanthemum (Dendranthema grandiflorum Kitamura cv. Pinky) grown under different restricted root zone volumes (30, 100, and 300 ml). Shoot growth was reduced with decreased root zone volume, but, the growth reduction was smaller when the plants were fertigated 8 times per day rather than once per day. Although the evapotranspiration rate did not decrease when the plants were fertigated frequently, the rate decreased significantly when the total water consumption nearly equaled the water-holding capacity of the medium (50% of the volume), especially in 30-ml or 100-ml containers. Stomata size decreased with a decrease in fertigation frequency and container size. The percentage of open stomata (open / total stomata × 100) and consequently, transpiration rate, net photosynthetic rate, and leaf CO₂ concentration were significantly lower in the plants grown in 30-ml and 100-ml containers, and fertigated once per day, compared to the four other treatments. The rates of photosynthesis and evapotranspiration of the plants fertigated 8 times per day remained faster than those fertigated only once per day. Consequently, vegetative growth of the plants fertigated frequently was equal to or more vigorous than those grown with three fold greater root zone volume but fertigated only once per day.