**4. Discussion**

**Figure 7.** Effect of pinching treatments (shoot removal) on weekly marketable fruit yield in determinate-type tomato. Pinch-3 or -6 indicates pinching treatment with the plant left with three or six true leaves, respectively. Different letters within each week indicate significant difference at *P* < 0.05 (Tukey's test). Vertical bars indicate standard error (Source:

parameter per secondary and higher lateral shoot in the three-true-leaf pinching treatment was highest among the all treatments. The number of flowered lateral shoots per whole plant in the three-true-leaf pinching treatment was significantly lower compared with those in the

**Table 2.** Effect of pinching treatments (shoot removal) on the number of flowers, flowering lateral shoots, flowers per lateral shoots, and secondary and higher lateral shoots per primary lateral shoot in determinate-type tomato (Source:

Control 198.5 ba 9.2 b 21.6 a 5.4 a 16.2 a 4.5 a Pinch-3b 158.3 a 4.8 a 33.5 c 5.0 a 27.9 c 6.4 c Pinch-6 239.6 c 9.0 b 26.8 b 5.1 a 21.8 b 5.4 b

**Number of flowers per lateral shoot Number of secondary** 

**higher**

**Total Primary Secondary and** 

**and higher lateral shoots per primary lateral shoot**

**Figure 7** shows the effect of pinching treatments (shoot removal) on the weekly marketable fruit yield. At 0 week after the start of the harvest (WAH), the weekly yield in the control was higher than those in both pinching treatments. However, at 1 WAH in the three-trueleaf pinching treatment was higher compared with that in the control. The weekly yield in the six-true-leaf pinching treatment at 2 WAH was also higher compared with that in the

Ohta and Ikeda [29]).

other treatments.

a

b

**Treatment Number of flowers per whole plant**

Modified from Ohta and Ikeda [29]).

**Number of flowered lateral shoots per whole** 

Different letters within each column indicate significant difference at *P* < 0.05 (Tukey's test).

Pinch-3 or -6 indicates pinching treatment with the plant left with three or six true leaves, respectively.

**plant**

44 Physical Methods for Stimulation of Plant and Mushroom Development

Flower bud removal or shoot removal was carried out to clarify the roles of TFB and AB at the first node below TFB, and to clarify the reason that lateral shoots at the second node below TFB elongate. In indeterminate-type cultivar, the lateral shoot lengths at the second node below TFB were suppressed significantly at 6 and 9 days after flower bud removal, but these shoots did not elongate upon shoot removal (**Figure 3**). In determinate-type cultivar, growth of the lateral shoots at the second node below TFB was not suppressed by flower bud removal compared with untreated plants, but lengths of these shoots increased significantly at 6 and 9 days after shoot removal (**Figure 4**). Hence, these results suggest that TFB promoted the growth of lateral shoots at the second node below TFB in indeterminate-type cultivar, but not in determinate-type cultivar (**Figure 5**). In contrast, the presence of AB at the first node below TFB seemed to suppress elongation of AB at the second node in both types of cultivars. Because emergence of TFB occurred earlier than emergence of AB at the second node [28], the effect of TFB on lateral shoot growth might be stronger than that on AB in both types of cultivars.

In relation to the inner plant growth regulators, auxin is produced in the apical bud and young expanding leaves in *Arabidopsis*, Brussels sprouts, pea, and tomato [30–33]. In the indeterminate-type cultivars, if the auxin concentration that suppresses lateral shoot elongation decreases temporarily upon ablation of the apical meristem or emergence of TFB, the lateral shoot at the second node below TFB elongates due to high cytokinin concentrations in the main stem. According to Shimizu-Sato et al. [34], reduced auxin concentration in the apical organs is a factor involved in increased cytokinin concentrations. However, in determinatetype cultivars, emergence of TFB did not promote the growth of lateral shoots. The much shorter stem lengths in determinate-type cultivars compared indeterminate-type cultivars [28] suggests that auxin concentrations in the apical organs including TFB might differ much from those of non-flowering terminal buds. Furthermore, auxin concentrations in apical organs including TFB might be related to branching habit in tomato plants. Some researchers [35–39] reported that plant growth regulators such as auxin, cytokinin, and strigolactone are related each other to the outgrowth of AB in several plants. Further study is desired to clarify the differences between the two branching types in tomato and the fluctuations in plant growth regulator concentrations.

In the pinching treatments (shoot removal), the growth of lateral shoots, especially in the threetrue-leaf pinching treatment, was greater compared with that in the control (**Table 1**), which would be due to the increase of mineral nutrients uptake since the distribution of some mineral nutrient elements was changed by the pinching treatment. The differences in lateral shoot lengths in the plants by the pinching treatment at four to six true leaves were larger than in the plants by the pinching treatment at zero to three true leaves in the determinate-type tomato "Wase Daruma" [14]. Almost the same result was obtained in regard to the lateral shoot lengths in the different pinching treatments in the present study. The shoot lengths of 3-scaffold shoots by pinching treatment were longer than those of 6-scaffold shoots because the nutrient competition among the remaining shoots reduced in watermelon (*Citrullus lanatus*) [39]. This might be the reason that at 59 DAT the mean lateral shoot lengths in the three-true-leaf pinching treatment were more uniform compared with those in the six-true-leaf pinching treatment. In this study, perhaps the emergence period of AB was shorter and the competition for absorbed mineral nutrients was reduced in the plants that underwent the three-true-leaf pinching treatment.

with large leaf areas. The number of flowers in tomato plants is also increased by higher contents of N and P [54]. Decoteau [55] reported that topping enhanced axillary leaf development in processing tomato cultivars. Thus, pinching treatments likely increase the photosynthetic products and mineral nutrient uptake by increasing the leaf areas of lateral shoots, and also likely lead to increased numbers of flowers. Therefore, it was revealed that the numbers of dropped flowers in the control and six-true-leaf pinching treatments were greater than in the three-true-leaf pinching treatment because of the excessive number of flowers per plant.

Branch Formation and Yield by Flower Bud or Shoot Removal in Tomato

http://dx.doi.org/10.5772/intechopen.71519

47

In tomato plants, flower bud or shoot removal (pinching treatment) affected the branch formation and fruit yield. The emergence of TFB affected the growth of lateral shoots in indeterminatetype cultivar, whereas it did not affect the growth of lateral shoots in determinate-type cultivar. Therefore, it is suggested that the appropriate management of the lateral shoots would be necessary for improve fruit yield or fruit quality, and it would be different between indeterminate and determinate-type cultivars. In indeterminate-type cultivars, it would be important to consider both the position and timing of shoot pinching and the timing of lateral shoot removal. In determinate-type cultivars, it might be necessary to study the number of lateral shoots or the training direction of the vines in order to avoid plant diseases during the periods of high temperature and/or humidity conditions. The shortening of harvest term and increase of initial fruit production in the three-true-leaf pinching treatment would be due to elongated lateral shoots and shortening of the flowering periods per plant. Thus, the pinching treatment could permit machine harvesting and save labor costs for determinate tomato cultivation. From these results, further studies should be undertaken to elucidate the relationships among shoot growth of plant, number of flowers, and physiological factors such as the sink strength in each organ, the distribution of photosynthetic products, and the changes of nutritional status and some plant growth

substances in plants after flower bud or shoot removal (pinching treatment).

Department of Agricultural and Forest Sciences, Shimane University, Matsue, Japan

[1] Saito T. Chap. 2. Flower bud differentiation and development of fruit vegetables. Section 1 flowering habit, Section 2 Differentiation process of flower bud. In: Vegetable crop Science. Vegetables. Tokyo: Rural Culture Association; 1982. p. 64-87 (in Japanese)

Address all correspondence to: ohta@life.shimane-u.ac.jp

**5. Conclusion**

**Author details**

Katsumi Ohta

**References**

Since the flowering period in the three-true-leaf pinching treatment was significantly shorter than those in the other treatments, the decrease of fruit set ratio that could occur during periods of high air temperatures (over 35°C) might have been avoided by pinching treatment [40]. Although the number of flowers in the three-true-leaf pinching treatment was significantly decreased compared with the other treatments (**Table 2**), there was no difference in the total fruit yield among all the treatments because the fruit set ratio in the three-true-leaf pinching treatment was higher than that in the other treatments. The harvest term in the pinching treatments was shortened until 3 WAH compared with that in the control until 4 WAH (**Figure 7**). These findings are in agreement with those of earlier studies [26, 27, 41]. The possibility for both shortening the harvest term and increasing the early yield was recognized in the threetrue-leaf pinching treatment. In particular, shortening of the harvest term would permit mechanical harvesting and save labor cost, as described previously [12, 42–44].

The number of flowers per primary lateral shoot was not different in all treatments, whereas the numbers of flowers per secondary and higher lateral shoots in the both pinching treatments were significantly higher compared with that in the control (**Table 2**). The flower numbers on the longer lateral shoots could be increased in processing tomato plants [45]. In eggplants, the flower numbers on pinched plants were higher than those on no pinched plants because the number of lateral shoots would be increased on the former [46]. Therefore, in this experiment, the increases in both the number of flowers and the number of secondary and higher lateral shoots in the both pinching treatments compared with the control might be due to the release of apical dominance in plants because of the extension of lateral shoots in the previous reports [17, 19, 20, 47].

Pinching (shoot removal) releases apical dominance and removes a metabolic sink in plants [38]. This results in decreased auxin production in the apical bud and increased nutrient distribution into and growth of the lateral shoots [48, 49]. The levels and distribution of N, P, and K were increased in the lateral shoots of bean plants in relation to apical dominance [50]. Ca, a structural component of the cell wall and membranes, is needed for tomato plant growth at early growth stages [51], and its uptake under high-growth conditions was increased in tomato shoots [52, 53]. Fukui et al. [13] also reported that increased the number of flowers were due to the relatively greater availability of photosynthetic products in tomato cultivars with large leaf areas. The number of flowers in tomato plants is also increased by higher contents of N and P [54]. Decoteau [55] reported that topping enhanced axillary leaf development in processing tomato cultivars. Thus, pinching treatments likely increase the photosynthetic products and mineral nutrient uptake by increasing the leaf areas of lateral shoots, and also likely lead to increased numbers of flowers. Therefore, it was revealed that the numbers of dropped flowers in the control and six-true-leaf pinching treatments were greater than in the three-true-leaf pinching treatment because of the excessive number of flowers per plant.
