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Table 2 The influence of constant and changing temperatures on the percentage of reproductive buds and the mean floral development stage of dissected buds of spurs and extension shoots of the apple cultivars ‘Summerred’ and ‘Discovery’ after completion of 12 weeks of exposure to the indicated temperatures (2016 experiment)

From: Temperature control of shoot growth and floral initiation in apple (Malus × domestica Borkh.)

Cultivar Temperature (°C) Spurs Extension shoots
Generative buds (%) Mean floral development stage (1–7)a Generative buds (%) Mean floral development stage (1–7)
‘Summerred’ 12 °C cont. 35.0 bb 2.3 c 0.0 d 1.0 d
15 °C cont. 100 a 6.6 b 37.4 c 2.0 c
18 °C cont. 100 a 7.0 a 63.5 a 4.4 a
21 °C cont. 100 a 7.0 a 67.2 a 4.7 a
Ambient 100 a 6.8 ab 64.6 b 3.5 b
  1218 °C 94.4 A 6.0 B 51.1 B 2.6 D
1521 °C 92.3 A 6.8 A 66.9 A 5.0 A
1812 °C 100 A 7.0 A 66.1 A 4.2 C
2115 °C 100 A 7.0 A 66.5 A 4.6 B
‘Discovery’ 12 °C cont. 0.0 d 1.1 e 1.5 e 1.1 e
15 °C cont. 100 a 6.8 b 36.4 c 3.9 a
18 °C cont. 94.4 b 6.4 c 62.8 a 3.6 b
21 °C cont. 100 a 7.0 a 45.3 b 2.7 c
Ambient 75.0 c 2.7 d 28.2 d 1.7 d
  1218 °C 64.3 B 2.7 D 49.3 C 1.8 B
1521 °C 100 A 3.7 C 53.4 A 2.2 B
1812 °C 100 A 6.7 A 51.4 B 3.1 A
2115 °C 85.7 AB 6.1 B 51.8 B 3.3 A
Probability level of significance by ANOVA
 Source of variation
  Cultivar (A)   < 0.001 < 0.001 0.001 0.001
  Temperature (B)   < 0.001 < 0.001 < 0.001 < 0.001
  A × B   < 0.001 < 0.001 < 0.001 < 0.001
  1. The data are means of all spur buds from each of the five replicate trees and of all lateral buds along the entire length of five extension shoots from each tree
  2. aStage 1 denotes entirely vegetative buds, and stage 7 denotes fully differentiated primary flowers
  3. bFor separation of means, Tukey’s multiple comparison test was performed separately for the two cultivars (lower case letters), and likewise for constant and changing temperatures (capital letters)