Condicionamento fisiológico de aquênios de girassol, sob estresses térmico e hídrico

Abstract

Sunflower production may be influenced by plant density, requiring uniformity in the initial growth phase. This may be influenced by water availability, as well as by soil temperature from germination through emergence. The priming technique has been used to reduce the period between germination and seedling emergence in the filed, providing better performance under stress conditions. Hence, an experiment was performed to evaluate the effect of three seed priming methods in sunflower achenes physiological quality, under different temperatures and water substrate potential. Thus, sunflower, cv. Catissol 01 achenes were submitted to artificial aging at 45°C for 0, 24 and 36 hours, to obtain three different lots. The achenes of each lot were submitted to osmopriming in KNO3 and polyethyleneglycol (PEG) 6000 solution and to hydropriming with subsequent drying. Following, lots were divided into two sub-lots, the first one being immediately evaluated and the second kept under controlled conditions and evaluated two months after storage. Achenes were submitted to germination tests at zero, 15, 35 e 45°C and at zero, -0,3, -0,6 e -0,9 MPa and tests of vigour (first counting, electrical conductivity, accelerated aging, emergence of seedlings and speed of seedlings). Results indicated that osmopriming with PEG solution after two month storage, improved germination and vigor, measured by first counting test, of lots aged for 24 hours under -0.3 MPa. Osmopriming with KNO3 solution also improved germination and vigour of the unaged lot, at the first counting test under 15°C, on both evaluations. Under hydropriming, vigour increase, measured by accelerated aging test, was only found in 36 hour artificially aged lots. During storage, maintenance of germination under 15°C on the lot achenes artificially aged for 36 hours, under 25°C on the the unaged lot and under under -0.3 MPa on the unaged lot occurred after osmopriming with PEG solution . Maintenance of germination under -0.3 MPa on the unaged lot after osmopriming with KNO3 solution also occurred.