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Cucurbit Genetics Cooperative Report 9:47-50 (article 13) 1986

Effect of Pot Size on Growth and Flowering of Cucumbers in the Greenhouse

Todd C. Wehner and Rufus R. Horton, Jr.

Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609

Cucumbers grow rapidly compared to most crop species, so that it is possible to get 3 to 5 generations per year in a breeding program using greenhouse facilities. Four generations per year is possible if the plants flower within 6 weeks of planting so that pollinations can be made in time to allow up to 6 weeks for the seeds to mature and up to 1 week to harvest and replant the greenhouse. It is often difficult to stay on a 13-week generation time due to the extra labor requirements of planting, pollination and harvest times.

Researchers with other crops have been successful in getting more generations per year by crowding the plants. Goulden (2) proposed the idea of using growth chambers to speed the growth of small grains by crowding. Grafius (3) applied the method by planting barley and oats in greenhouses using sand culture. Water was applied as needed, but fertilizer was given only 2 to 3 times. The plants remained small and produced only 0 to 4 (rarely 0) seeds per inflorescence. Many plants could be advanced in a small space in less time under this system. The system was modified by Brim (1) for his single-seed descent breeding method. Robbins and Pharr (4) grew cucumber plants in pots ranging from 0.4 to 5.9 1 in volume to restrict root growth. Water and nutrients were provided to prevent stress, and shoots were given unlimited growth space in the greenhouse. However, the shoots were proportionally smaller on plants with restricted root size (root/shoot ratio remained constant).

Peterson (personal communication) found that seeds could be harvested 4 weeks after pollination, cleaned with high pressure water, dried for 1 day, soaked in acetone for 1 day, incubated at 32 ˚ C in petri plates containing moist vermiculite, and transplanted to pots 1 day later. That method saves 2 weeks on post-pollination seed development time, and 1 week on fermentation, drying and packeting time. Thus, with gynoecious plants, it is possible to go from seed to seed in 10 weeks for 5 generations per year.

In working with genotypes that grow fairly large, and are not as rapid to flower and set seed, it would be desirable to reduce further the generation time. It is possible that if cucumber plants were crowded into a small space they would grow smaller, flower faster, and set seeds sooner than normal. The objective of this study was to determine whether growing plants in small pots could reduce the generation time of cucumbers in the greenhouse.

Methods. The experiment was a randomized complete block with 2 cultivars, a gynoecious inbred pickle (Gy 14A) and a monoecious inbred sliver (Poinsett 76). Plants were grown in one of 4 pot sizes (10, 13, 15, 0or 20 cm diameter), and fruits were either held on the plants without watering 2, 4, or 6 weeks after pollination (summer, 1983), or harvested 2, 4, or 6 weeks after pollination (spring, 1984).Data were collected at fruit harvest time. The vine length, fruit weight, number of seeds per fruit, weight per seed, and percentage of germination at 22 ˚ C were measured. Also, the number of days from planting to first pistillate flower was recorded.

Results. Plants grown in large pots had longer vines and heavier fruits than those grown in small pots (Tables 1 and 2). The larger fruits had more seeds, but the weight per seed did not change. Days to flower and percentage of germination of the harvested seeds did not change with pot size, except that no seeds were produced from fruits harvested 2 weeks after pollination. Although 'Poinsett 76' flowered as soon as Gy 14A, the flowers were staminate for the first 5 to 10 days (data not shown). Thus, for monoecious lines, self-pollinations cannot be made until 41 to 49 days after planting (Tables 1 and 2). The extra 1 to 2 weeks time for pollination of monoecious lines would make it possible to get 4 generations a year, but not 5 (as is possible for gynoecious lines).

Thus, it is possible to change the size of the plant and the number of seeds per fruit by using larger pot sizes. However, plants grown in small pots do not flower or reach mature seed stage sooner than those grown in large pots. Although there were occasional problems of small seeds and poor germination of seeds from plants grown in 10 cm diameter pots, it was possible to get sufficient seed numbers from plants grown in 13 to 20 cm diameter pots. Two weeks after pollination, watering could be stopped and seeds would still develop properly (Table 1). However, fruits harvested 2 weeks after pollination did not have viable seeds (Table 2). It required 4 weeks for seeds to develop sufficiently for good germination.

Plants grown in 13 cm pots with fruits harvested 4 weeks after pollination provided 90 to 296 seeds per fruit that were plump and germinated well. That appeared to be the minimum satisfactory system of the treatment combinations tested.

Table 1. Effect of pot size nad weeks to end of irrigation on plant and fruit growth for summer, 1983 greenhouse cropz .

Cultivar
Weeks of watery
Pot dia., (cm)
Vine length (cm)
Fruit weight (g)
Seed no.
Weight per seed (mg)
% germination
Days to 1st flower
Gy 14 A
2
10
102
25
74
22
100
37
13
136
23
52
27
100
38
15
180
35
61
21
100
38
20
308
103
213
28
100
37
 
4
10
132
37
82
16
98
38
13
135
28
90
21
98
40
15
206
65
60
27
100
38
20
290
50
67
26
100
41
 
6
10
75
20
45
26
95
37
13
126
40
61
25
98
37
15
236
68
197
18
100
38
20
390
95
219
28
100
38
Poinsett 76
2
10
176
16
39
25
100
49
13
192
40
125
23
100
49
15
264
53
179
25
100
43
20
306
75
172
27
100
49
 
4
10
108
28
99
16
95
49
13
157
48
142
21
100
49
15
323
65
102
27
100
47
20
300
120
118
27
100
49
 
6
10
204
45
87
23
100
48
13
220
40
149
25
100
43
15
347
117
202
28
100
43
20
451
118
210
24
100
49
LSD (5%)
86
31
109
10
4
3
CV (%)
19
27
55
20
2
5

z  Data are means of 2 replications.
y Irrigation of pots stopped 2, 4, or 6 weeks after pollincation.

Table 2. Effect of pot size and weeks to harvest on plant and fruit growth for summer, 1984 greenhouse cropz.

Cultivar
Weeks to harvest
Pot dia. (cm)
Vine length (cm)
Fruit weight (g)
Seed no.
Weight per seed (mg)
% germination
Days to 1st flower
Gy 14 A
2
10
74
201

0

0
0
37
13
102
411
0
0
0
29
15
107
347
0
0
0
35
20
108
333
0
0
0
33
 
4
10
87
350
160
26
100
36
13
92
496
228
26
100
36
15
110
567
251
28
100
35
20
126
522
231
32
100
36
 
6
10
91
354
189
22
88
35
13
100
507
225
26
100
35
15
107
595
221
29
93
34
20
14
624
218
29
100
36
Poinsett 76
2
10
158
170
87
12
50
46
13
144
291
0
0
0
45
15
172
418
0
0
0
43
20
218
435
0
0
0
45
 
4
10
122
366
234
14
45
46
13
164
534
296
25
100
45
15
182
532
197
25
90
44
20
195
665
230
28
100
45
 
6
10
176
439
277
18
85
45
13
176
631
260
27
100
42
15
193
727
235
29
100
41
20
154
641
311
26
98
45
LSD (5%)
36
150
143
5
43
4
CV (5)
13
16
45
10
34
6

z  Data are means of 2 replications.

Literature Cited

  1. Brim, C.A. 1966. A modified pedigree method of selection in soybeans., Crop. Sci. 6: 220.
  2. Goulden, C.H. 1939. Problems in plant selection. p. 132-133. In R.C. Punnett (ed.), Proc. 7th Internat. Genet. Cong. Cambridge Univ. Press, London.
  3. Grafius, J.E. 1965. Short cuts in plant breeding. Crop Sci. 5: 377.
  4. Robbins, N.S. and D,M. Pharr. 1985. Effect of restricted roots on shoot growth and carbohydrate metabolism of Cucumis sativus L. leaves. HortScience 20(3) : 536 (abstr.).
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Department of Horticultural Science Box 7609North Carolina State UniversityRaleigh, NC 27695-7609919-515-5363
Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 25 March, 2010