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Role of K + in leaf growth: K + uptake is required for light‐stimulated H + efflux but not solute accumulation
Author(s) -
STILES K. A.,
VAN VOLKENBURGH E.
Publication year - 2004
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 - 10.1111/j.0016-8025.2004.01144.x
Subject(s) - apoplast , turgor pressure , biophysics , efflux , auxin , coleoptile , chemistry , elongation , ion transporter , guard cell , growth inhibition , cell wall , membrane , membrane transport , cell growth , biochemistry , biology , materials science , ultimate tensile strength , gene , metallurgy
The stimulation of dicotyledonous leaf growth by light depends on increased H + efflux, to acidify and loosen the cell walls, and is enhanced by K + uptake. The role of K + is generally considered to be osmotic for turgor maintenance. In coleoptiles, auxin‐induced cell elongation and wall acidification depend on K + uptake through tetraethylammonium (TEA)‐sensitive channels (Claussen et al ., Planta 201, 227–234, 1997), and auxin stimulates the expression of inward‐rectifying K + channels (Philippar et al . 1999). The role of K + in growing, leaf mesophyll cells has been investigated in the present study by measuring the consequences of blocking K + uptake on several growth‐related processes, including solute accumulation, apoplast acidification, and membrane polarization. The results show that light‐stimulated growth and wall acidification of young tobacco leaves is dependent on K + uptake. Light‐stimulated growth is enhanced three‐fold over dark levels with increasing external K + , and this effect is blocked by the K + channel blockers, TEA, Ba ++ and Cs + . Incubation in 10 m m TEA reduced light‐stimulated growth and K + uptake by 85%, and completely inhibited light‐stimulated wall acidification and membrane polarization. Although K + uptake is significantly reduced in the presence of TEA, solute accumulation is increased. We suggest that the primary role of K + in light‐stimulated leaf growth is to provide electrical counterbalance to H + efflux, rather than to contribute to solute accumulation and turgor maintenance.