Stomatal Conductance and Stomatal Resistance Studies in Relation to Haulm Yield in Potato

The experiment was laid out in Rabi season(2009-2010 and 2010-2011). IRGA instrument (LI-6400XT) was used for estimation different microclimatic parameters of the crop within the height of 2 mt. In general, during both seasons, there was a rapid increase in mean stomatal conductance from early growth stage to 56 days and thereafter it gradually decreased towards maturity of the crop.Highest mean values of stomatal conductance were recorded at 56 DAP interval as 0.38 and 0.52 mol. m^-2 s^-1 in 2009 and 2010, respectively. Further, there was also gradual increase in mean stomatal resistance from early growth stage towards maturity of the crop. Lowest mean values of stomatal resistance were recorded at 28 DAP interval as 4.21 and 3.28 mol. m^-2 s^-1 in 2009 and 2010, respectively. Increased stomatal conductance appeared to be the reason for the first peak whereas for the second peak non stomatal characters may be responsible. Stomatal resistance governs photosynthesis and transpiration. Decrease in soil moisture content increased stomatal resistance. High temperature was associated with decreased stomatal resistance. Stomatal resistance is affected by many factors including PAR, leaf age, air temperature and the CO₂ concentration. Analysis of the relationship between PAR, leaf age, air temperature and the CO₂ concentration at the various growth stages for the different treatments showed that 1.2 IW/CPE ratio and planting on 44th MW with mulching treatment proved to be superior to the other treatments. It is observed from the data that during both the years of experimentation, of haulm yield (q ha^-1), mulching produced significantly higher mean values of these haulm yield (q ha^-1) than without mulching. The haulm production which was reduced by the effect of water stress on stem growth and reduction in number of branches, as well as to a limited extent on the tubers themselves.