Water relations and physiology at the milk grain development stage, and growth, gran yield and mineral content of potted wheat plants under long mild water deficit [Dataset]

Comprises 3 sheets: 1. Leaf morphological traits. 2. Physiological traits. 3. Chl fluorescence traits 4. Final productivity. 5. Mineral content. Description of methods used for collection/generation of data: (a) ‘leaf morphological traits’: traits were determined at early milk grain development (growth stage 73 (Z73) according to the Zadoks scale (Zadoks et al., 1974). The mass of the dry-oven flag leaves was measured after their incubation in an oven at 60 ºC for 48 h. Leaf area was determined using an electronic planimeter Li-COR Model Li-3050A (Lincoln, ME, USA). (b) ‘physiological traits’: samples were collected during two consecutive days at Z73. Ψleaf was determined using a Schölander pressure chamber instrument Model 1000 (PMS Instrument Company, Albany OR), after maintaining the flag leaves in a humid and cold ambient for 25 min to achieve water equilibrium. RWC was calculated after determining fresh mass, dry mass and 24-h water-saturated mass of the flag leaves. The Chl content was measured using Dualex instrument (FORCE-A, Paris, France) (Goulas et al., 2004). Photosynthesis traits (Aatm, Eatm, gs, atm, Ci, atm, WUEins, atm) were determined with the portable photosynthesis system CIRAS-3 (PP System, Amesbury, MA) and parameter settings were as follows: 22 ºC; light intensity, 1500 μmol m−2 s−1 with a blue:green:red LED ratio of 38:37:25; cuvette flow of air, 250 cm3 min−1 and relative humidity, 50%. The flag leaves were powdered and stored at −80 ºC. Samples were extracted in ethanol/water to assess the content of NO3- and FAA. NO3- content was measured in the soluble ethanol/water extracts as described in the study by Cawse(1967) with minor modifications to accommodate it to a 96-well microplate reader. The total content of FAA was determined by the ninhydrin colorimetric method as described in the study by (Vicente et al., 2016). The content of Pro, AsA and GSH was extracted and spectrophotometrically determined as described in the study by Bendou et al.(2022). (c) ‘chl fluorescence components’: Chl fluorescence related traits (Fv/Fm, ΦPSII, ΦNPQ, ΦNO) were measured using a portable fluorometer PAM 2000 (Walz, Effeltrich, Germany). The whole plant remained in the dark for 30 min before starting a dark-light induction curve within the slow-kinetic window for 30 min (Kasajima et al., 2009). (d) ‘final productivity’: samples were collected at maturity and final harvest after senescence. The number of ears per plant, grain yield per ear (GYE), grain number per ear (GNE) and the oven-dry mass of the above- and underground components of the plants were computed after drying them in an oven at 60 ºC. (d) ‘mineral content’: Flag leaves and grains from final harvest at maturity were separated to measure their mineral composition. The content of C and N in powdered flag leaves and grains was determined by the Dumas combustion method using a C-N analyser Leco model CHN-628 (LECO Corporation, St. Joseph, MI) as described in the study by (Pereira et al., 2023). The content of P, K, Ca, Mg, S, Mn, Fe, Cu, Zn, Mo and Na was determined by inductively coupled plasma atomic emission spectroscopy using an ICP-OES model Varian 720-ES (Agilent, Santa Clara CA). All the samples were dried in an oven at 105 ºC for 12 h. An amount of 0.5 g of each sample was weighed and digested in a microwave digestion system model EthosTM Up (Milestone Srl, Italy) using a volume of 10 mL of 65% HNO3 and 30% H2O2 in a ratio of 8:2 (v:v) and a temperature of 200 ºC for 15 min. The digested samples were finally diluted with ultrapure water to 25 mL before ICP-OES analysis.

In this research study, we evaluated the effect of mild water deficit on the physiological response of the flag leaf at the milky grain development stage and the final grain yield and mineral content at maturity of bread wheat (Tritticum aestivum cv Gazul). Three plants were grown in 5-L pots containing a mixture of perlite and vermiculite in a volumetric ratio of 3 to 1 as the soilless substrate and under greenhouse conditions from February 2023 to July 2023. After seed sowing, the potted plants were fertigated at full-holding capacity (100% FC) three days per week. After the unfolding of the fourth leaf, pots were divided into two blocks: one half of the pots followed the same fertigation pattern at 100% FC while fertigation was reduced to 65% FC in the other half until plant maturity and senescence. At the milky grain development stage, when plants water demand was highest, we assessed leaf morphological traits, photosynthesis related traits, content of proline, free amino acids, ascorbic acid, glutathione and nitrate at two consecutive days. At maturity, plants were harvested to determine final biomass, water use efficiency, grain yield, and mineral content of the flag leaves and the grains.

Research was funded by MCIN/AEI/10.13039/501100011033 (Project nº PID2019-107154RB-100) and the regional government of Castilla y León (Project nº CSI260P20). The Project ‘CLU-2019–05—IRNASA/CSIC Unit of Excellence’ funded by the Junta de Castilla y León and co-financed by the European Union (ERDF ‘Europe drives our growth’) and the CSIC Interdisciplinary Thematic Platform (PTI) Optimization of Agricultural and Forestry Systems (PTI-AGROFOR) are also acknowledged.

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