Fig. 4.

Diurnal gas-exchange responses of glasshouse-grown Bulnesia retama stems experiencing varying degrees of drought. Plots show responses over a 13 h light–11 h dark period in well-watered and droughted B. retama stems from glasshouse-grown plants. The responses shown are net CO₂ assimilation rate (A; A, D, G, J), stomatal conductance (g_s; B, E, H, K) and the ratio of intercellular to ambient partial pressure of CO₂ (C_i/C_a; C, F, I, L) in stems of glasshouse-grown B. retama plants. (A–C) Responses of well-watered plants. (D–F) Responses of moderately droughted stems. (G–I) Responses of severely droughted plants. (J–L) Responses during extreme drought. Experiments began at 12:00 h. Each response is from one representative plant. The grey dashed line in the C_i/C_a plots indicates 1.0. Grey shading in each panel indicates the nocturnal period.