Cucurbit Genetics Cooperative Report 7:17-18 (article
8) 1984
Growth Analysis of Three Cucumber Lines Differing in Plant Habit
and Yield
D.R. Ramirez and T.C. Wehner
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
It is known that the activity of a developing fruit in a cucumber
plant inhibits the development of fruit that set later (1), as
well as the development of other plant parts (2). This
inhibitory effect ceases when the growing fruits are removed from
the plant, allowing the production of several fruit per plant
under multiple harvest conditions. The prevention of
simultaneous development of several fruit per plant greatly
reduces yield of fruit, especially in once-over harvest systems.
One explanation for this inhibitory effect could be that fruits
of the commercial cultivars of Cucumis sativus L.
constitute strong sinks for assimilates, drawing heavily on plant
supplies and inhibiting in this way the development of other
fruit. Inhibition or cessation of vegetative growth could
indirectly limit the ability of a plant to support the growth of
more fruit. This study was run to advance our understanding of
the partitioning of assimilates in cucumber plants. The
objective of this experiment was to determine relationships
between vegetative and reproductive plant parts throughout the
entire cycle of development of 3 lines that differ in growth
habit and yield.
Methods. Growth analysis studies of 3 lines differing in
growth habit and yield were conducted in the Horticultural
Science greenhouses in Raleigh, NC during the Fall, 1982. The 3
lines studied were LJ 90430, an accession of Cucumis
sativus var. hardwickii; 'Calypso', a widely-used
indeterminate cultivar; and M 21, a dwarf, determinate breeding
line for NCSU. After germination, plants of LJ 90430 were
subjected to a 9.5 hour daylength for 17 days in order to induce
fruit set.
The experiment design was a split plot in a randomized complete
block with 4 replications. Whole plots were the 9 harvests and
subplots were the 3 lines. Harvests were made 32, 39, 46, 53,
60, 67, 74, 81 and 88 days after planting beginning November 2
and ending December 28. At each harvest, one whole plot in each
replication was removed and the following measurements made:
fresh and dry weights of leaves, stems fruits, and roots; number
of leaves, fruits and branches; stem length, and leaf area. Leaf
area was determined with an electronic leaf area meter. After
each harvest, the border plants were moved in to fill the space
left.
Results. At the end of the growing period (88 days), both
LJ 90430 and 'Calypso' produced the same amount of total dry
weight and fruit dry weight. However, M 21 produced
significantly less total dry weight. LJ 90430 incorporated a
higher amount of dry weight into leaves, stems and roots than the
other 2 lines (Table 1).
Table 1. Partition of dry weight production into leaves, stems,
fruits and roots in three lines at final harvest (88 days)z. |
Line |
Dry Weight (g) |
Leaves |
Stems |
Fruits |
Roots |
Total |
LJ 90430 |
10.2 |
9.9 |
40.9 |
2.6 |
63.1 |
Calypso |
8.1 |
5.3 |
43.7 |
1.7 |
53.2 |
M 21 |
7.0 |
3.0 |
24.3 |
0.7 |
35.3 |
|
LSD (5%) |
1.3 |
0.8 |
12.6 |
0.9 |
15.1 |
CV (%)
| 9 |
8 |
20 |
31 |
17 |
zData are means over four replications on a per plant basis. |
'Calypso' produced a significantly higher total fresh weight and
fruit fresh weight than LJ 90430 and M 21 (Table 2). When dry
and fresh weights were compared, it was evident that 'Calypso'
fruits and stems had a higher water content. The number of
fruits per plant were significantly higher in LJ 90430 than in
the other 2 lines.
Table 2. Fruit number,and fresh weight of leaves, stems and
fruits in three lines at final harvest (88 days)z |
Line |
Fresh Weight (g) |
Leaves |
Stems |
Fruits |
Roots |
Total |
LJ 90430 |
26 |
79 |
120 |
504 |
703 |
Calypso |
3 |
76 |
86 |
769 |
930 |
M 21 |
2 |
73 |
43 |
468 |
585 |
|
LSD (5%) |
4 |
16 |
13 |
108 |
123 |
CV (%) |
24 |
12 |
9 |
11 |
10 |
zData are means over four replications on a per plant basis. |
Leaf photosynthetic area was higher in 'Calypso' in the first 2
harvests (32 and 39 days), but LJ 90430 had a significantly
higher leaf area than 'Calypso' and M 21 thereafter. This early
advantage of 'Calypso' and to a lesser extent M 21 was related to
earliness. Fruits started developing when plants were 39 days
old in 'Calypso' and M 21, and when plants were 53 days in LJ
90430. At this time their leaf area had developed 63, 59 and
93%, respectively, of their total mean leaf area for the
remainder of the period when it was fully developed (Table 3).
Table 3. Leaf area per plant for nine weekly harvests in three
linesz. |
Line |
Leaf area per plant (cm) |
Days from planting to
harvest |
32 |
39 |
46 |
53 |
60 |
67 |
74 |
81 |
88 |
LJ 90430 |
74 |
1928 |
3734 |
5153 |
5715 |
5744 |
5601 |
5583 |
5395 |
Calypso |
123 |
2489 |
3604 |
4025 |
3770 |
3832 |
3980 |
4082 |
4086 |
M 21 |
105 |
1928 |
3106 |
3547 |
3473 |
3254 |
2958 |
3151 |
3252 |
|
LSD (5%) |
15 |
560 |
806 |
717 |
885 |
906 |
759 |
995 |
1075 |
CV (%) |
9 |
15 |
13 |
10 |
12 |
12 |
11 |
13 |
15 |
zData are means over four replications. Analysis were performed
separately for each of the nine harvests. |
These results indicate that 'Calypso' was capable of producing
the same amount of total dry weight and a significantly higher
total fresh weight and fruit fresh weight with a lower leaf
photosynthetic area. However, the inhibitory effect of fruits in
'Calypso' and in M 21 was very high. It could be that early
fruit set at the time when leaf area has not developed fully
could enhance this inhibitory effect.
Literature Cited
- Denna, D.W. 1973. Effect of genetic parthenocarpy and
gynoecious flowering habit on fruit production and growth of
cucumber, Cucumis sativus L. J. Amer. Soc. Hort. Sci.
98:602-604.
- McCollum, J.P. 1934. Vegetative and reproductive responses
associated with fruit development of the cucumber. Cornell
Agric. Exp. Sta. Memoir 163:1-27.
