Influence of Windbreak-Shelter on Light Interception, Stomatal Conductance, and CO\u3csub\u3e2\u3c/sub\u3e-Exchange Rate of Soybeans, \u3ci\u3eGlycine max\u3c/i\u3e (Linnaeus) Merrill

Interception of photosynthetically active radiation, CO2-exchange rate, stomatal conductance, and leaf water potential of windbreak-sheltered and exposed soybeans were studied in the field. Within-canopy profiles of photosynthetically active radiation measured after canopy closure indicated deeper light penetration into the canopy of sheltered soybeans. Consequently, plants in shelter had higher CO2-exchange rates and greater stomatal conductance at equivalent relative canopy heights in comparison with unsheltered plants. Since no vertical gradient of leaf water potential was observed in the canopy in either treatment, gradients of CO2-exchange rate and stomatal conductance were solely responses to light. Mean CO2-exchange rates of top, fully expanded, canopy leaves of six soybean cultivars tested were significantly greater for sheltered plants. This was a consequence of greater leaf water potential and stomatal conductance. Selection of soybean cultivars on the basis of these physiological responses to shelter should lead to increased exploitation of the windbreak microclimate for soybean production