Photosynthetic Water Use Efficiency of Heritage and Modern Potatoes under Limited and Unlimited Water Environments

Abstract

Photosynthetic capacity for heritage (Taewa) and modern potato cultivars were compared at different water and nitrogenregimes in the glasshouse and field. The glasshouse was 2*2*4 factorial design with two irrigation: 100% ET and 60% ET; two applied N: 50 kg N ha -1 and 200 kg N ha -1 , two Taewa (Moe Moe, Tutaekuri) and two modern potatoes (Moonlight, Agria). The 2009/2010 field experiment was a split-plot, with irrigation and rain-fed regimes as the main treatments: four potatoes above were sub-treatments. The 2010/2011 field experiment was a split-split-plot, with three water regimes as the main treatments: three cultivars (Moe Moe, Tutaekuri, and Agria) were subplots; two N rates were sub-sub-treatments. Gaseous exchange was measured by CIRAS-2 at different days from emergence. Leaf water potential was measured using pressure chamber method. Taewa achieved high photosynthetic WUE in glasshouse and 2010/2011 experiment by maintaining high A n , low g s and low Ci compared to modern cultivars (p < 0.0001). The A n , g s and T increased with irrigation and N increase while decreasing Ci (p < 0.01). Water stress significantly increased VPD resulting in low A n and photosynthetic WUE in Moonlight in the glasshouse. The leaf water potential for Taewa was very tolerant while modern potatoes were weakened by water stress. The study indicated that Taewa can be scheduled at partial irrigation without more detri mental effects on photosynthetic capacity while modern potatoes need full irrigation to avoid detri mental effects on photosynthetic capacity.