Variation in Responses of Photosynthesis and Apparent Rubisco Kinetics to Temperature in Three Soybean Cultivars.

Bunce Bunce

doi:10.3390/plants8110443

Abstract

Recent in vivo assays of the responses of Rubisco to temperature in C3 plants have revealed substantial diversity. Three cultivars of soybean (Glycine max L. Merr.), Holt, Fiskeby V, and Spencer, were grown in indoor chambers at 15, 20, and 25 °C. Leaf photosynthesis was measured over the range of 15 to 30 °C, deliberately avoiding higher temperatures which may cause deactivation of Rubisco, in order to test for differences in temperature responses of photosynthesis, and to investigate in vivo Rubisco kinetic characteristics responsible for any differences observed. The three cultivars differed in the optimum temperature for photosynthesis (from 15 to 30 °C) at 400 μmol mol−1 external CO2 concentration when grown at 15 °C, and in the shapes of the response curves when grown at 25 °C. The apparent activation energy of the maximum carboxylation rate of Rubisco differed substantially between cultivars at all growth temperatures, as well as changing with growth temperature in two of the cultivars. The activation energy ranged from 58 to 84 kJ mol−1, compared with the value of 64 kJ mol−1 used in many photosynthesis models. Much less variation in temperature responses occurred in photosynthesis measured at nearly saturating CO2 levels, suggesting more diversity in Rubisco than in electron transport thermal properties among these soybean cultivars.

Highlights

The temperatures at which crop leaves accomplish photosynthesis vary diurnally, seasonally, and with geographic location
Much less variation in temperature responses occurred in photosynthesis measured at nearly saturating CO2 levels, suggesting more diversity in Rubisco than in electron transport thermal properties among these soybean cultivars
Intraspecific variation in the response and acclimation of photosynthesis to temperature has been studied extensively since the first infra-red CO2 analyzers came into use in plant physiology [1,2]

Summary

Introduction

The temperatures at which crop leaves accomplish photosynthesis vary diurnally, seasonally, and with geographic location. Soybeans grown in North America are subject to a wide range of both growth and midday the south, while midday mean temperatures during the growing seasons range from a low of about temperatures, even without considering extreme temperature events. Study soybeans grown photosynthetic in North America are subject to a wide range of both growth of and middaywhen grown at three growth temperatures in order to determine whether significant variation in response temperatures, even without considering extreme temperature events. The hypothesis was would be insignificant in photosynthetic response to moderate response exists within to identify which kinetic parameters may be involved in any temperatures among thesesoybeans, soybeanand cultivars. The hypothesis was that there would be insignificant variation in photosynthetic response to moderate temperatures among these soybean cultivars

Results

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Materials and Methods