The physiological responses of potato (Solanum tuberosum L) cultivars to soil drought at the tuberization phase and their impact on agronomically important traits were investigated in potted plants under semi‐controlled conditions. Genotype‐dependent responses of potato to water deficiency were evaluated on two pairs (tolerant/sensitive) of Polish cultivars. Each pair of cultivars had a similar genetic background but was extremely different in terms of drought tolerance evaluated on the basis of loss of tuber yield under field conditions. The results clearly indicate different mechanisms of tolerance to water deficiency and the ability to recover from soil drought in two tolerant but genetically unrelated cultivars. When subjected to soil drought, the cultivar Gwiazda had low rates of transpiration and photosynthesis and low levels of stomatal conductance due to hypersensitivity to ABA, but its maximal photochemistry efficiency and PSII performance index were unchanged. Another strategy was displayed by the dehydration‐avoidant cultivar Tajfun, which kept the stomata partially open. Thus, the plants were able to retain a relatively high rate of photosynthesis over transpiration. The parameters measured for cultivar Tajfun for photosynthesis and transpiration were the same after plant rewatering, similar to the control plants. This was not the case for the cultivar Gwiazda. The ability of plants to regenerate after soil drought relief appears to be a good indicator of potato susceptibility to soil drought and allows the yield of potato tubers to be predicted. The physiological traits identified in closely related potato cultivars but differed in their drought tolerance seem to be useful for genetic engineering and breeding programmes.

Magnesium (Mg) is one of the significant macronutrients which is involved in the structural stabilisation of plant tissues and many enzymes such as PSII. The latter efficiency and performance were analysed, using chlorophyll (Chl) a fluorescence induction kinetics and microscopic images, to detect the changes in structure and function of photosynthetic apparatus of radish plants grown under Mg deficiency (Mgdef). Plants grown under Mgdef showed less PSII connectivity and fewer active primary electron acceptors (QA) oxidizing reaction centres than control plants. Confocal and electron microscopy analyses showed an increased amount of starch in chloroplasts, and 3,3'-diaminobenzidine (DAB)-uptake method revealed higher H2O2 accumulation under Mgdef. Prominent changes in the Chl a fluorescence parameters such as dissipated energy flux per reaction centre (DIo/RC), relative variable fluorescence at 150 µs (Vl), and the sum of the partial driving forces for the events involved in OJIP fluorescence rise (DFabs) were observed under Mg deficiency. The latter also significantly affected some other parameters such as dissipated energy fluxes per cross-section (DIo/CSo), performance index for energy conservation from photons absorbed by PSII antenna until the reduction of PSI acceptors (PItotal), and relative variable fluorescence at 300 µs (Vk). This work emphasises the use of chlorophyll fluorescence in combination with microscopic and statistical analyses to diagnose the effects of nutrients deficiency stress on plants at an early stage of its development as demonstrated for the example of Mgdef. Due to the short growth period and simple cultivation conditions of radish plant we recommend it as a new standard (model) plant to study nutrients deficiency and changes in plant photosynthetic efficiency under stress conditions.

Enhancing plant productivity and mitigating the impact of environmental stressors require a thorough understanding of phytomonitoring and physiological features indicative of plant health. This study delves into the response of cucumber plants...