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Rapid, reversible alterations in spinach thylakoid appression upon changes in light intensity
Author(s) -
Rozak P. R.,
Seiser R. M.,
Wacholtz W. F.,
Wise R. R.
Publication year - 2002
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.0016-8025.2001.00823.x
Subject(s) - thylakoid , spinach , photosynthesis , chloroplast , shading , irradiance , ultrastructure , light intensity , biophysics , chlorophyll fluorescence , chlorophyll a , botany , biology , chemistry , optics , biochemistry , physics , art , gene , visual arts
Changes in light quantity and quality cause structural changes within the thylakoid membrane; long‐term responses have been described for so‐called ‘sun’ and ‘shade’ leaves. Many leaves, however, experience changes in irradiance on a time scale of minutes due to self‐shading and sun flecks. In this study, mature, attached spinach leaves were grown at 300 µ mol photons m −2 s −1 then rapidly switched to a different light treatment. The treatment irradiances were 10, 800 or 1500 µ mol m −2 s −1 for 10 min, or 10 or 20 min of self‐shading (about 10 µ mol m −2 s −1 ). Image analysis of transmission electron micrographs revealed that a 10 min switch to a lower light intensity increased grana size and number per chloroplast profile by 10–20%. Returning the leaves to 300 µ mol m −2 s −1 for 10 min reversed the phenomenon. Chlorophyll fluorescence measurements of detached, intact leaves at 77 K were suggestive of a transition from state 2 to state 1 upon shading. Diurnal ultrastructural measurements of granal size and number did not reveal a significant net change in ultrastructure over the time scale of hours. It is concluded that spinach chloroplasts can alter the degree of thylakoid appression in response to irradiance changes on a time scale of minutes. These ultrastructural responses are caused by biochemical and biophysical adjustments within the thylakoid membrane that serve to maximize photosynthesis and minimize photo‐inhibition under rapidly fluctuating light environments.