Photosynthesis, biochemical activity, and leaf anatomy of tree tomato (Solanum betaceum Cav.) plants under potassium deficiency

The effects of potassium (K) deficiency on the physiological, biochemical, and anatomical parameters of leaves in the tree tomato plants (Solanum betaceum Cav.) were evaluated during vegetative growth. The experiment was carried out for 135 days after treatment applications under greenhouse conditions, employing the nutrient solutions with the following treatments: control plants (without K deficiency) and the plants with K deficiency. The light response curve, photosynthesis at light saturation (Amax), light compensation point (Ic), transpiration rate (E), stomatal resistance (SR), and pigment contents in leaves were evaluated. Additionally, the maximum photochemical efficiency of PSII (Fv/Fm), contents of malondialdehyde (MDA), total soluble sugars, proline, and leaf anatomy parameters were assessed. In the K-deficient plants, the reduction in Amax (66%), Ic (63.7%), E (66%), Fv/Fm (17.3%), contents of total chlorophyll (77.4%) and chlorophyll a (52%), thickness of leaf blade L (28.5%), palisade parenchyma PP (6.5%), and spongy parenchyma SP (9.5%) were observed, compared to the control plants. In contrast, the variables that increased significantly were SR (65%), MDA (52%), Upper epidermis thickness (Ue) (27.1%), and Lower epidermis thickness (Le) (22.3%). The potassium deficiency caused alterations in the plant development due to the influence on physiological, biochemical, and anatomical parameters, which suggests the importance of mineral nutrition with K for this plant.