Each flower cluster on 10 new shoots of 5 years old Delaware grape vines grown on the sandy hill region were dipped in the gibberellin solution of 100 and 50 ppm at one to three times before and after flowering period in various combinations, and effects on the flowering period, the rate of seedless fruit, sugar to acid ratio, fruit development and ripening period were investigated.
Experimental design was as fo11ows.
<tt>
│ Treatment before flowering │ Treatment after flowering
Plot │ ─────────────────────────────────
│ Date │ Date
│ │──────────────────
│ │ Ist treatment │ 2nd treatment
───────────────────────────────────────
A-I │ April 30th │ ─────── │ ────────
A-II │ 〃 〃 │ June 14th │ ────────
A-III │ 〃 〃 │ 〃 〃 │ June 21st
───────────────────────────────────────
B-I │ May 7th │ ─────── │ ────────
B-II │ 〃 〃 │ June 14th │ ────────
B-III │ 〃 〃 │ 〃 〃 │ June 21st
B-IV │ 〃 〃 │ ─────── │ 〃 〃
───────────────────────────────────────
C-I │ May 12th │ ─────── │ ────────
C-II │ 〃 〃 │ June 14th │ ────────
C-III │ 〃 〃 │ 〃 〃 │ June 21st
C-IV │ 〃 〃 │ ─────── │ 〃 〃
───────────────────────────────────────
D-I │ May 17th │ ─────── │ ────────
D-II │ 〃 〃 │ June 14th │ ────────
D-III │ 〃 〃 │ 〃 〃 │ June 21st
D-IV │ 〃 〃 │ ─────── │ 〃 〃
───────────────────────────────────────
</tt>
Date of full bloom of no treated plot was June 5th.
Each plot was apart treated by 100 and 50 ppm solution

1) The flowering period of 100 ppm treatment was faster one day than 50ppm one. The flowering period of 100ppm treatment became faster 7 days on A (April 30th), 6 days on B (May 7th), 5 days on C (May 12th), 4 days on D (May 17th) than that of no treated one.
2) The rates of seedless fruits of D・II and D-III plot dipped in 100ppm solution were the highest (97%) in all 100ppm treatments and that of D-I plot dipped in 100ppm solution was 96%, but others did not show high seedless fruit ratios.
The seedless fruit ratios were generally low on 50ppm treatments and each seedless fruit ratio of D-II and D-III plot was 96% but others dipped in 50ppm solution were not effective.
3) Each sugar content of two 100ppm treatments -D-II and D-III plot -was over 18% on July 25th, but sugar content of each 50ppm treatrnent was lower than 18%.
Sugar contents of fruits dipped in 50ppm solution on May 17th-D-II and D-III plot -became also over 18% On July 29th.
4) The fastest ripening period in all 100ppm treatments was 2 days faster than that of 50ppm.
The clusters of D-II and D-III plot that treated by 100ppm solution ripened the most rapidly on July 25th and the ripening periods of D-II and D-III plot of 50ppm were also the fastest in 50ppm treatments and ripened on July 27th.
5) Each berry weight of D-II and D-IIi plot treated by 100ppm solution was the heaviest in all treated plots, but those were lighter than those of no treated one and each berry weight of 50 ppm treatment was very light.
Each cluster weight of D-II and D-III plot reated by 100ppm solution was the heaviest in all treated plots and heavier than that of no treated one, but those of 50ppm treatment were small a little and were as similar as no treated one.
6) The germination % of pollens treated by 50 and 100ppm gibberellin solution was very low or none.
7) When it rained within 6 hours after dipping of gibberellin solution, the seedless fruit ratio became very low.
8) For early shipment of Delaware grape, about 2.6g gibberellin to 10a was used by this dipping method.