**2. Materials and methods**

tomatoes that are cultivated mainly for the fresh market. On the contrary, determinate-type tomatoes with a self-pruning growth habit with only short sympodial branches form a few flower trusses [3]. These cultivars are mainly grown for processing and cooking tomatoes [4]. In general, the lateral shoots of indeterminate tomato cultivars are periodically removed to prevent nutrient competition between vegetative and reproductive organs during cultivation period. Several lateral shoots extends greatly unless all the lateral shoots are removed [5]. Since the sink strength of lateral shoots with flower buds and trusses is stronger than that of the main stem or lateral shoot without flower buds and trusses [6], strong growth of some lateral shoots may cause uneven distribution of photosynthetic products, resulting in undesirable effects on fruit production. As an example of using lateral shoots, during tomato cultivation during winter in the Netherlands, lateral shoots generated from the first or second nodes below TFB are used to increase stem numbers per area in indeterminate cultivars and increase tomato yield [7]. The utilization of lateral shoots can both promote high-quality fruit production [8–10] and also increase crop yield [11]. In contrast, for determinate tomato cultivars, lateral shoots are generally not removed to save labor and ensure yield [12–15]. However, lack of fruit set on the first flower truss due to low or high temperatures or rainfall or due to pinching at the seedling stage could affect the lateral shoot lengths and flowering

Differentiation of AB occurs at every node during the growth of most commercial cultivars. Although AB at lower nodes extends during the vegetative stage, AB at the upper nodes below TFB does not extend much due to apical dominance [1, 16]. When TFB at the shoot apex emerges and grows, the entire AB in general begins to elongate. Branch formation in indeterminate cultivars differs from that in determinate ones because of generally remaining the lateral shoots. Also, to investigate the growth properties of lateral shoots generated from

The growth of lateral shoots in the indeterminate cultivars can be extended by pinching (shoot removal) from the results of the previous reports [17–20]. In some tomato cultivars, the numbers and weights of fruits that grew on double-stemmed plants created by pinching treatments were greater than those that grew on single-stemmed plants [21–23]. Pinching at the seedling stage can increase the number of double clusters and flowers on lateral shoots of cherry tomatoes [24, 25]. Pinching is often performed to increase initial tomato yield, but there are differences among cultivars as to the effects of pinching [26, 27]. In addition, the lengths of the lateral shoots at each node do differ depending on the pinching position [14]. As the number of remaining true leaves is increased by pinching, there is a difference among the lateral shoot lengths. Since a relationship among the lengths of lateral shoots, the number of flowers per plant, and per lateral shoot is expected to be changed by pinching in determinate processing tomatoes, growth of the lateral shoot would be influenced by the uptake and distribution of mineral nutrients in each organ. Furthermore, because pinching can enhance the uniformity of fruit maturity [14], pinching could shorten the harvest term while also, due to this shorter flowering period, leading to harvest periods with more than 80% total fruit yield. However, there has been little research to elucidate the relationships between the TFB and the elongation of lateral shoots in indeterminate and determinate-type tomatoes. Furthermore,

each node could be used to increase productivity in tomato cultivation.

periods of determinate processing tomatoes.

36 Physical Methods for Stimulation of Plant and Mushroom Development

## **2.1. Lateral shoot elongation after terminal flower buds (TFB) and shoot (including TFB and axillary bud (AB) at the first node below TFB) removal**

#### *2.1.1. Plant materials, cultivation, and treatments*

Indeterminate-type "Mini Carol" (*Solanum lycopersicum* l.) (Sakata Seed Co. Ltd., Japan) and determinate-type "Suzukoma" (Tohoku Agricultural Research Center, National Agriculture and Food Research Organization and ZEN-NOH, Japan) were used for this experiment. Seeds were sown in plastic containers (34.5 × 27.0 × 7.5 cm). One plant was potted black plastic pots at a ratio of sandy loam:bark compost of 1:1 (v/v). Tomato plants were transplanted into Wagner pots (1/5000 a) in the same potting substrate described above. All pots were placed in a greenhouse at Shimane University, Matsue, Japan. TFB (maximum bud length of about 1 mm) were removed by pinching them off, and the stems were decapitated at the upper portions of shoots of the second node below TFB (**Figure 1**). Ten plants per treatment were evaluated.

#### *2.1.2. Measurements*

The lateral shoot length of the second node below TFB was measured at 0, 3, 6, and 9 days after the treatments.

**Figure 1.** Axillary bud of the second node (AB-S) below the terminal flower bud (TFB) in indeterminate-type cultivar "Mini Carol" (a) and determinate-type cultivar "Suzukoma" (b) tomatoes. Axillary buds (AB) of the first node below TFB exist behind TFB. Flower bud removals are shown by bars (Source: Ohta and Ikeda [28]).

### **2.2. Effects of pinching treatment (shoot removal) on plant growth, flowering, and yield in determinate tomato**

coder (Sumigraph NC-22F, Sumitomo Chemical Analysis Center Corp., Tokyo). The phosphorus (P) contents were measured by vanadomolybdate absorption spectrometry. The potassium (K), calcium (Ca), and magnesium (Mg) contents were measured by an atomic absorption spectrophotometer (AA-630, Shimadzu, Kyoto, Japan). The contents of mineral nutrient in each organ of plant were calculated from dry weight and mineral nutrient concentrations. The first flowering dates of the main stem and the lateral shoots were recorded, and the numbers of flowers, and the number of secondary and higher lateral shoots per primary lateral shoot were counted. Full ripe fruits were harvested twice per week during 6 weeks, and the number of fruits, fruit weight, and the number of marketable fruits were recorded. The soluble solids content (SSC) values of 20 marketable fruits were evaluated using a digital refractometer (APAL-1; AS ONE Corp., Osaka, Japan) to measure the Brix

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

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

39

**3.1. Lateral shoot elongation after TFB or shoot removal in indeterminate tomato**

The lateral shoot length at the second node below TFB in the indeterminate-type cultivar "Mini Carol" was significantly suppressed by flower bud removal at 6 and 9 days after treatment, compared to that in untreated plants (**Figure 3**). On the other hand, lateral shoot lengths at the second node below TFB did not differ after shoot removal compared with

**Figure 3.** Lateral shoot length of the second node below the terminal flower bud (TFB) after flower bud removal and shoot removal at the upper position of second node below TFB of indeterminate cultivar, "Mini Carol". Significant difference was shown as \*\*: *P* < 0.01, NS: not significant (*t*-test). Vertical bars indicate standard error (Source: Ohta and

values of fresh juice samples.

**3. Results**

untreated plants.

Ikeda [28]).

#### *2.2.1. Experimental site, plant materials, growing conditions, and treatments*

The determinate-type "Shuho" (Nagano Chushin Agricultural Institute Experimental Station, Shiojiri, Japan) was used for this experiment. Seeds were sown in plastic containers. All containers were placed in a greenhouse at Shimane University, Matsue, Japan. One plant was potted black plastic pots at a ratio of sandy loam:bark compost of 1:1 (v/v). After the third and sixth true leaves had expanded, the plants were pinched at the stem above the third and sixth true leaves (**Figure 2**). No pinching treatments were performed in the untreated control. The tomato plants were transplanted into the experimental field with the soil surface covered with black 0.02-mm polyethylene film at Yatsuka-cho, Matsue, Japan. The plants were arranged in a single 1.6 m wide row, with 0.8 m spacing between rows, 0.45 m spacing between plants, and a planting density of 1.39 plants m−2. A randomized complete block design was used with three replicates. In total, eight plants per treatment were used. Six plants were used to measure the lateral shoot growth, flowering, and fruit yields, and the remaining plants were used to analyze the mineral nutrient contents.

#### *2.2.2. Measurements*

At 18 and 59 days after transplanting (DAT), the lengths of the lateral shoots generated from each node were measured. At 18 DAT, the plants were sampled and divided into stems, leaves on the main shoot, and lateral shoots, and then washed with deionized water. After being air-dried at 80°C for 72 h, the dried plants were ground using an electric mill (WB-1; AS ONE Corp., Osaka, Japan). Total nitrogen (N) contents were determined using a CN

**Figure 2.** Pinching treatments (shoot removal) in determinate-type tomato (schematic diagram). Left is control (a), center is Pinch-3 (b), and right is Pinch-6 (c). Pinch-3 or -6 indicates pinching treatment with the plant left with three or six true leaves, respectively. A is terminal flower bud (TFB) of main stem. X is pinching position.

coder (Sumigraph NC-22F, Sumitomo Chemical Analysis Center Corp., Tokyo). The phosphorus (P) contents were measured by vanadomolybdate absorption spectrometry. The potassium (K), calcium (Ca), and magnesium (Mg) contents were measured by an atomic absorption spectrophotometer (AA-630, Shimadzu, Kyoto, Japan). The contents of mineral nutrient in each organ of plant were calculated from dry weight and mineral nutrient concentrations. The first flowering dates of the main stem and the lateral shoots were recorded, and the numbers of flowers, and the number of secondary and higher lateral shoots per primary lateral shoot were counted. Full ripe fruits were harvested twice per week during 6 weeks, and the number of fruits, fruit weight, and the number of marketable fruits were recorded. The soluble solids content (SSC) values of 20 marketable fruits were evaluated using a digital refractometer (APAL-1; AS ONE Corp., Osaka, Japan) to measure the Brix values of fresh juice samples.
