خشکی Gaillardia grandiflora اثر بسترهای مختلف کشت و محلول پاشی ملاتونین بر شاخصهای رشدی و فیزیولوژیک گل رعنا زیبا.

Effects of Different Growing Substrates and Melatonin Foliar Application on Growth and Physiological Traits of Gaillardia grandiflora under Drought Stress Conditions.

This study aimed to investigate the effects of different growing media and melatonin foliar application on the growth and physiological traits of Gaillardia grandiflora under drought stress. The experiment was conducted in a factorial arrangement based on a CRD with three replications in a greenhouse and included three irrigation levels (100%, 70%, and 40% of field capacity), five growing media (soil alone, soil + 30% well-decomposed cow manure, soil + 30% leaf compost, soil + 30% perlite, and soil + 30% peat–cocopeat), and melatonin foliar application (200 μM and control). Results showed that severe drought stress (40% field capacity) significantly reduced the number of flowers per plant, flower diameter, stem height, and aboveground dry weight up to 1.6 g. Organic-rich media, particularly leaf compost and peat–cocopeat, improved leaf relative water content up to 89%, increased proline accumulation up to 5.8 mmol g-1 and flavonoids up to 0.9 mg g-1, and reduced ion leakage. Melatonin application had a more pronounced effect on physiological traits, enhancing plant defense capacity and leaf water balance, while flower production was dependent on the growing media and irrigation level. The highest flower number (57 flowers) was recorded in the treatment with 70% field capacity × leaf compost × without melatonin, whereas melatonin showed its greatest effect in maintaining physiological indices and increasing drought tolerance. These results indicate that a combination of moderate irrigation management, organic-rich growing media, and melatonin can enhance sustainable growth and drought resilience of Gaillardia grandiflora. [ABSTRACT FROM AUTHOR]

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