Journal Article

The influence of supra-optimal root-zone temperatures on growth and stomatal conductance in <i>Capsicum annuum</i> L.

I.C. Dodd, J. He, C.G.N. Turnbull, S.K. Lee and C. Critchley

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 51, issue 343, pages 239-248
Published in print January 2000 | ISSN: 0022-0957
Published online January 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.343.239
The influence of supra-optimal root-zone temperatures on growth and stomatal conductance in Capsicum annuum L.

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Pepper (Capsicum annuum L.) plants were grown aeroponically in a Singapore greenhouse under natural diurnally fluctuating ambient shoot temperatures, but at two different root-zone temperatures (RZTs): a constant 20±2 °C RZT and a diurnally fluctuating ambient (A) ( 25–40 °C) RZT. Plants grown at 20-RZT had more leaves, greater leaf area and dry weight than A-RZT plants. Reciprocal transfer experiments were conducted between RZTs to investigate the effect on plant growth, stomatal conductance (gs) and water relations. Transfer of plants from A-RZT to 20-RZT increased plant dry weight, leaf area, number of leaves, shoot water potential (𝚿shoot), and gs; while transfer of plants from 20-RZT to A-RZT decreased these parameters. Root hydraulic conductivity was measured in the latter transfer and decreased by 80% after 23 d at A-RZT. Transfer of plants from 20-RZT to A-RZT had no effect on xylem ABA concentration or xylem nitrate concentration, but reduced xylem sap pH by 0.2 units. At both RZTs, gs measured in the youngest fully expanded leaves increased with plant development. In plants with the same number of leaves, A-RZT plants had a higher gs than 20-RZT plants, but only under high atmospheric vapour pressure deficit. The roles of chemical signals and hydraulic factors in controlling gs of aeroponically grown Capsicum plants at different RZTs are discussed.

Keywords: Capsicum; root temperature; growth; high-temperature stress; stomata; chemical signalling.; A-RZT, ambient root-zone temperature; A⇒20-RZT, plants grown initially at A-RZT then transferred to 20-RZT; gs, stomatal conductance; Lp, root hydraulic conductivity; RZT, root-zone temperature; 𝚿leaf, leaf water potential; 𝚿shoot, shoot water potential; 20-RZT, root-zone temperature of 20±2 °C; 20⇒A-RZT, plants grown initially at 20-RZT then transferred to A-RZT; VPD, atmospheric vapour pressure deficit; [X-ABA], xylem sap ABA concentration; [X-NO−3 xylem sap nitrate concentration.

Journal Article.  5840 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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