Effects of exogenous spermidine on chloroplast ultrastructure in tomato seedlings under salinity-alkalinity stress.

Data were measured in the second expanded leaves (numbered basipetally) after salinity-alkalinity treatment for 4 days. SL, stroma lamellae; GL, grana lamellae; SG, starch grains; P, plastoglobuli. Scale bars for mesophyll cells, chloroplasts, and thylakoids are 2, 0.5, and 0.1 µm, respectively.