The seeds of two radish genotypes, G1-Laal Pari and G2-Early Milo were acquired from Ayyub Agricultural Research Institute (AARI), Faisalabad-Pakistan. The present research was conducted during the summer (2022) in the old Botanic Garden, the University of Agriculture, Faisalabad (31° 25’44” N, 73° 04’ 18” E, altitude 186 m a.s.l.) to evaluate the effect of exogenously applied α-Toc (Sigma-Aldrich, St. Louis, MO, USA) on Radish under drought conditions. Eight seeds of each variety were relocated to round plastic pots (radius 11 cm and depth 25 cm) filled with 8 kg of soil and poly lining on the bottom of the plants to prevent the leaching of α-Toc. Before seedling, the soil was adequately prepared, following the prerequisites for radish. A factorial experiment was designed as completely randomized design (CRD) with four replications. Two radish genotypes were arranged in 32 pots to apply the drought and alpha-tocopherol (α-Toc) treatments. The average day and night range 20–25 °C and 10–19 °C, respectively, and the photoperiod ranges 10–12 h with relative humidity (RH) ranging from 58.9 to 60.1% on average. During the first two weeks, plants were subjected to normal irrigation levels. After two weeks of completion, irrigation was halted for half of two variants to simulate the drought conditions. Before drought implications, the field capacity (FC) of two pots was monitored by filling them with 8 kg of oven-dried soil overflowing with normal water and leaving them for 1 day on a steel wire stand. When no dripping of water was seen, both of the pots were weighed to determine the saturated weight (SW); after the oven dried at 72 °C for 2 days, soil dry weight (DW) was measured. The percentage of moisture contents was calculated using the following equation [23 ].
Drought stress (DS) was imposed on selective pots of the experimental replicates. For DS stress, 38 ± 3% FC was maintained for a whole growing season and acclimation to the designated drought-level was maintained within two weeks and irrigation was gradually decreased for a two weeks to prevent from sudden evaporative loss. The pots were weighed daily to assess the FC and irrigated as per requirement accordingly to sustain the needed FC. During the DS treatments, the normal FC was provided to absolute controls and parts were reshuffled to prevent border and pseudo-replication effects. Before α-Toc foliar applications the α-Toc solution was prepared in a nominal amount of the methanol and the final volume was maintained by distilled water (dH2O) having a pH of 7.0., a total volume of 20 mL per pot was used. A preliminary experiment was carried out with different concentrations of α-Toc (0, 20, 40, 100 ppm) to ensure positive and negative effects on radish seedlings under drought and sole applications. According to growth results, 100 ppm demonstrates the best sustainability outcomes during drought and sole conditions. Consequently, 100 ppm of α-Toc was used for the main experiment. The foliar exogenous applications of the α-Toc were applied after 30 days of the establishment. The exogenous applications of α-Toc were done before evening to prevent evaporative loss and maximum absorption by the leaves. To enhance the absorption of α-Toc, 0.1% Tween-20, a non-ionic surfactant, was used to reduce the surface tension on the leaf surface. The plant sampling was done after two weeks of drought and α-Toc applications to prevail various growth and biochemical attributes.
Drought stress (DS) was imposed on selective pots of the experimental replicates. For DS stress, 38 ± 3% FC was maintained for a whole growing season and acclimation to the designated drought-level was maintained within two weeks and irrigation was gradually decreased for a two weeks to prevent from sudden evaporative loss. The pots were weighed daily to assess the FC and irrigated as per requirement accordingly to sustain the needed FC. During the DS treatments, the normal FC was provided to absolute controls and parts were reshuffled to prevent border and pseudo-replication effects. Before α-Toc foliar applications the α-Toc solution was prepared in a nominal amount of the methanol and the final volume was maintained by distilled water (dH2O) having a pH of 7.0., a total volume of 20 mL per pot was used. A preliminary experiment was carried out with different concentrations of α-Toc (0, 20, 40, 100 ppm) to ensure positive and negative effects on radish seedlings under drought and sole applications. According to growth results, 100 ppm demonstrates the best sustainability outcomes during drought and sole conditions. Consequently, 100 ppm of α-Toc was used for the main experiment. The foliar exogenous applications of the α-Toc were applied after 30 days of the establishment. The exogenous applications of α-Toc were done before evening to prevent evaporative loss and maximum absorption by the leaves. To enhance the absorption of α-Toc, 0.1% Tween-20, a non-ionic surfactant, was used to reduce the surface tension on the leaf surface. The plant sampling was done after two weeks of drought and α-Toc applications to prevail various growth and biochemical attributes.
