Fig. 2

Chlorophyll index (SPAD units), thylakoid membrane damage (F_o/F_m ratio; unitless), quantum yield of PSII (ΦPSII; unitless), electron transport rate (μmol electrons m⁻² s^− 1), and components of seed yield per plant as a function of total root length (cm) under drought stress in wheat-alien chromosome lines (water withheld for 16 d). The CS check is shown as a white circle. The curve is fitted by a linear function. (a) chlorophyll index, y = 25.3 + 0.0013 x; r² = 0.21 (P < 0.01); (b) thylakoid membrane damage, y = 0.409–0.000014x; r² = 0.39 (P < 0.01); (c) quantum yield of PSII, y = 0.137 + 0.000024x; r² = 0.39 (P < 0.01); (d) electron transport rate, y = 82.4 + 0.011x; r² = 0.60 (P < 0.01); (e) seed set percentage, y = 13.083 + 0.0042x; r² = 0.52 (P < 0.001); (f) seed number per plant, y = 9.959 + 0.0028x; r² = 0.16 (P < 0.01); (g) individual seed weight, y = 4.142 + 0.0039x; r² = 0.35 (P < 0.001) and (h) seed yield per plant, y = − 0.217 + 0.0002x; r² = 0.54 (P < 0.001)