DILTA, B.S.THAKUR, ANIT2017-09-062017-09-062017http://krishikosh.egranth.ac.in/handle/1/5810030555HORTICULTUREABSTRACT The present investigation entitled, “Effect of plant spacing and GA3 application on seed yield and quality of sweet william (Dianthus barbatus L.)” was carried out at the Khaltoo experimental farm of Department of Seed Science & Technology, Dr Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Solan (HP) during 2015 to 2017. The experiment was laid out in RBD (Factorial) with 12 treatment combinations of four levels of spacing i.e. S1 (30 × 30 cm), S2 (30 × 25 cm), S3 (30 × 20 cm) and S4 (20 × 20 cm) and three doses of GA3 i.e. G0 (0 ppm), G1 (50 ppm) and G2 (100 ppm) replicated thrice. Among different levels of spacing, S1 (30 × 30 cm) recorded maximum values for days taken to first flowering (131.67 days), plant spread (38.78 cm), number of flowers per plant (106.11), size of flowers (1.86 cm), duration of flowering (39.11 days), number of capsules per plant (67.84), number of seeds per capsule (48.67), seed yield per plant (4.57 g), 1000 seed weight (0.99 g), germination percentage (88.67 %), seedling length (7.45 cm), seedling dry weight (4.81 mg), seed vigour index-I (662.72) and seed vigour index-II (428.84). Whereas, spacing S4 (20 × 20 cm) recorded maximum values for plant height (46.07 cm), number of flowers per plot (2600.00) and seed yield per plot (107.18 g). The application of GA3 @ 100 ppm resulted in highest values for plant height (42.67 cm), plant spread (36.54 cm), number of flowers per plant (96.75), number of flowers per plot (2349.75), size of flowers (1.83 cm), duration of flowering (36.75 days), number of capsules per plant (62.67), number of seeds per capsule (46.49), seed yield per plant (4.08 g), seed yield per plot (99.66 g), 1000 seed weight (0.96 g), germination percentage (86.25 %), seedling length (7.11 cm), seedling dry weight (4.68 mg), seed vigour index-I (617.28) and seed vigour index-II (406.13). The interaction, S1 × G2 i.e. a plant spacing of 30 × 30 cm along with application of 100 ppm GA3 recorded maximum values in terms of most of the growth, flowering, seed yield per plant and seed quality parameters. However, maximum seed yield per plot was found under the interaction S4 × G2 i.e. when spacing was kept 20 × 20 cm apart with the application of GA3 @ 100 ppm, but the effects were found to be non significant. So, it is concluded that for better growth, flowering, maximum seed yield and quality, the plants be spaced at 30 × 30 cm a part along with the application of GA3 @ 100 ppm.ennullThesis