Modeling Photosynthesis Decline of Excised Leaves of Sweet Corn Plants Grown with Organic and Chemical Fertilization

Summary The transpiration or photosynthesis decline curve of excised plant leaves has been used to predict water stress tolerance ability. This study analyzed the characteristics of the declining photosynthetic rate in excised leaves of sweet corn (Zea mays L.) plants after treatment with effective microorganisms (EM), a mixed culture of naturally occurring beneficial microorganisms, organic fertilizer (Bokashi) and chemical fertilizer. The net photosynthetic rates (P N) of intact leaves were measured using LI-6400 gas exchange system under 2000 μmol m−2 s−1 PPF. When P N reached the maximum (P max), the leaf was excised and P N was continuously monitored. A declining P N curve with time is obtained and modeled according to P N = [Pmax - P res (1 - βt)] e−α(t-τ) + P res (1 - βt), where t is the time elapsed after the leaf was excised; τ is the time point when the stomata begin to close; P res is the residual P N when stomatal closure completed; and α and β are constants related to stomatal and residual conductances respectively. Photosynthesis maintenance ability (PMA) is expressed as 1/(α+ β). Leaves of plants fertilized with organic materials and/or treated with EM showed a higher PMA and P N than the controls after the leaves were excised.