Reduced sensitivity to photoinhibition following frost-hardening of winter rye is due to increased phosphate availability
Hurry, Vaughan ; Gardeström, Per; Öquist, Gunnar
The possibility of a role for phosphate metabolism in the photosynthetic regulation that occurs during frost hardening was investigated in winter rye (Secale cereale L. cv. Musketeer). Leaves of frost-hardened and non-hardened winter rye were studied during photosynthetic induction, and at steady state after being allowed to take up 20 mM orthophosphate through the transpiration stream for 3 h. At the growth irradiance (350 mumol.m-2.s-1) frost-hardening increased the stationary rate Of CO2-dependent O2 evolution by 57% and 25% when measured at 5 and 20-degrees-C, respectively. Frost-hardening also reduced the lag phase to stationary photosynthesis by 40% at 5-degrees-C and decreased the susceptibility of leaves to oscillations during induction and after interruption of the actinic beam during steady-state photosynthesis. These responses are all indicative of increased phosphate availability in frost-hardened leaves. As reported previously by Oquist and Huner (1993, Planta 189, 150-156), frost-hardening also decreased the reduction state of Q(A), the primary, stable quinone acceptor of PSII, and decreased the sensitivity of winter rye to photoinhibition of photosynthesis. Non-hardened rye leaves fed orthophosphate also showed an increased photosynthetic capacity (25% at 20-degrees-C and light saturation), lower reduction state of Q(A), a reduced sensitivity to photoinhibition and lower susceptibility to oscillations resulting from a brief interruption of the actinic light. Thus, the data indicate that phosphate metabolism plays a key role in photosynthetic acclimation of winter rye to low temperatures.
COLD ACCLIMATION; FROST HARDENING; PHOSPHATE; PHOTOINHIBITION OF PHOTOSYNTHESIS; SECALE
1993, Volume: 190, number: 4, pages: 484-490
Publisher: SPRINGER VERLAG
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