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Table 4 Influence of constant and changing temperatures on shoot structure and flowering of apple trees as assessed by out-door performance in the subsequent spring following overwintering in a cold store at 1 °C (2017 experiment)

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

Cultivar Temperature (°C) Flowering nodes (%) Vegetative nodes (%) Non-breaking nodes (%) Nodes per tree Flower clusters per tree Flowers per tree Flowers per cluster Days to anthesis from Apr. 27a
‘Summerred’ 12 °C cont. 9.0 cb 82.2 a 8.8 b 158.0 b 14.3 d 41.0 c 2.9 bc 33.0 a
18 °C cont. 67.2 a 19.1 c 13.7 ab 165.0 b 111.0 b 455.0 a 4.1 a 27.0 bc
24 °C cont. 41.4 b 30.1 c 28.6 ab 395.7 a 164.0 a 491.3 a 3.0 bc 26.7 c
27 °C cont. 14.1 c 53.1 b 32.8 a 401.3 a 54.7 c 142.3 b 2.7 c 28.3 bc
Ambient 15.4 c 68.1 ab 16.5 ab 196.5 b 30.5 c 113.0 b 3.7 ab 29.5 b
  1224 °C 29.6 A 50.4 A 20.0 A 232.0 A 69.5 B 211.5 B 3.0 A 27.0 A
1827 °C 30.7 A 45.5 AB 23.8 A 243.0 A 76.0 B 281.5 B 4.0 A 28.0 A
2412 °C 30.8 A 48.7 A 20.5 A 187.5 A 58.5 B 230.5 B 4.0 A 26.5 A
2718 °C 41.6 A 29.8 B 28.7 A 312.5 A 130.0 A 469.5 A 3.6 A 27.0 A
Mean   29.7 48.5 21.8 263.7 78.6 264.1 3.4 28.3
‘Discovery’ 12 °C cont. 0.5 bc 65.6 ab 33.9 c 215.5 a 1.0 c 3.0 c 1.5 c 65.0 b
18 °C cont. 37.4 a 27.7 bc 34.9 bc 265.3 a 89.0 a 331.7 a 3.7 a 28.0 a
24 °C cont. 22.2 a 22.9 c 54.9 ab 326.0 a 74.0 a 200.5 a 2.8 b 26.5 a
27 °C cont. 6.5 ab 27.1 c 66.5 a 397.0 a 26.0 b 74.5 b 2.9 b 30.5 a
Ambient 3.6 b 68.3 a 28.1 c 241.5 a 8.5 c 20.0 c 2.3 bc 37.0 a
  1224 °C 0.0 C 63.3 A 36.7 B 187.5 B 0.0 C 0.0 C 0.0 B > 100 A
1827 °C 4.6 B 45.2 A 50.3 A 337.5 A 14.5 B 23.5 B 0.8 AB 66.0 B
2412 °C 11.3 AB 48.0 A 40.6 A 341.5 A 38.5 AB 122.5 AB 3.2 A 30.5 B
2718 °C 19.1 A 28.8 B 52.1 A 399.0 A 65.5 A 283.5 A 4.5 A 29.5 B
Mean   13.0 43.2 43.7 299.3 38.1 128.9 2.5 39.1
Probability level of significance by ANOVA
 Source of variation
  Cultivar (A)   ns ns ns ns ns ns 0.05 0.001
  Temperature (B)   < 0.001 < 0.001 0.01 < 0.001 < 0.001 < 0.001 0.02 0.04
  A × B   0.003 ns ns ns ns ns ns ns
  1. The data are means of two trees from each treatment
  2. aFor non-flowering trees, number of days is set to 100
  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)