Abstract:

The response characteristic of photosynthetic apparatus of potato plants under lowpotassium stress was analyzed, and the internal relations among the photosynthetic parameters were investigated. Results show that the contents of chlorophyll a, chlorophyll b and carotenoids in leaves decrease under lowpotassium stress. However, the effect of the content ratio of chlorophyll a/b was not obvious, that there was no significant difference during the treatment period (P>0.05). Variable fluorescence (Fv), PSII photochemical efficiency and potential activity in leaves under lowpotassium treatment were lower than those in control group. The drop in Fv was due to the increase in initial fluorescence (F0) and the decrease in the maximum fluorescence (Fm). In the early stage of lowpotassium stress, the drop in the net photosynthetic rate Pn was mainly induced by the stomatal limitation. With further extension of the stress time, the nonstomatal limitation gradually became a main factor for the drop in Pn. The response characteristic of photosynthesis of potato leaves under lowpotassium stress can be described by the nonorthogonal hyperbolic Farquhar model. The coefficient of determination of PnPAR response curve in each stage was higher than 0.92. The fitting analysis indicated that both the Apparent Quantum Yield (AQY) and the maximum apparent photosynthetic rate (Pmax) decreased obviously. However, the effects of potassium concentration on Light Compensation Point (LCP) and Dark Respiration Rate (Rd) were not significant.

Key words: potassium, stress, potato, photosynthetic physiology, response characteristic