Seed priming enhances root morphology parameters and improves growth of cucumber plants under non-favorable temperature conditions

Three equal samples of graded seeds of a commercial cucumber were used in the experiment. The first was used as control (ctr), the second was the subject of hydropriming (hp) and the third was the subject of osmopriming (op) by a polyethylene (PEG) osmotic solution (-1.5 bar). ‘hp’ and ‘op’ variants were incubated for 48 h at a germination room (24°C, 80% RH), then removed from the respective solutions, dried and kept for next 48 h at same conditions (24°C, 80% RH). The control variant was also kept at the same conditions for the last 48 h. Following that procedure, all seeds were sown in polysterol trays, filled with vermiculite (60 cm³ per each module) and transferred in two different growth chambers with different temperature regimes, respectively 18 and 24°C. Equal RH (80%) and lightening conductions (12 h, PPFD 180 µmol m^‑2 s^‑1). were applied. It was found that ‘op’ has significantly increased the dry matter, length, surface and volume of the root system compared with control plants, even under non favorable temperature conditions (18°C). There were positive effects of ‘hp’ regarding root morphology parameters, also, but only at optimum temperature conditions (24°C). A higher relative growth rate (RGR) was provided by ‘op’, therefore a higher plant weigh was obtained by ‘op’ plants under either non optimal or optimum growing conditions.