Simulated Acid Rain-induced Alterations in Flowering, Leaf Abscission and Pollen Germination in Sunflower ( Helianthus annuus   L.)

This study examined the effects of simulated acid rain (SAR) of different pH [distilled water-7.0 (control), 5.7, 4.5 and 3.0] on leaf abscission, flowering and pollen germination in sunflower (Helianthus annuus L.) cv. ‘Morden’ as test system under field conditions in sandy loam soil with sufficient organic matter, pale yellow in color and pH 7.3 and 65 % water holding capacity. Acid rain solution (30 ml/plant) was sprayed on plants at weekly intervals starting from two leaved stage till initiation of flowering in the early morning under natural environment. Evaluation of SAR effects on budding, flowering, leaf abscission and pollen development revealed that initiation and duration of budding and flowering altered significantly in test plant with decreasing pH of acid rain solution. Acid rain application showed early leaf abscission and reduction in pollen germination percentage and pollen tube length. Effects of SAR increased more dramatically with the increase of SAR acidity. The study indicates the sunflower plant turns to be an acid rain sensitive system and demands for breeding with acid rain tolerant varieties in view of expanding acid rain geographical areas and growing industrialization.

Keywords
Simulated acid rain; Helianthus annuus; flowering; leaf abscission; pollen germination; sunflower