原著論文
栽培時期および気温がトマトの茎上での花房位置に及ぼす影響
2017 年 86 巻 1 号 p. 70-77
詳細
2017 年 86 巻 1 号 p. 70-77
In the tomato (Solanum lycopersicum), the position of the inflorescence on the stem is known to affect the number of days to first anthesis and has commonly been characterized by the leaf-number (ordinal number from the oldest leaf) of the leaf just below the inflorescence (LEAF-BI) only by the appearance after extension of the stem near the inflorescence. Some examples showing that this evaluation was not suitable were observed by the authors. To confirm the reproducibility of the observation, experiments were conducted in which 4 cultivars were sown in a greenhouse 12 times from Oct. 2008 to Aug. 2010. Based on the vertical positional relationship between the base of the first, second, or third inflorescence and the base of the last initiated leaf before inflorescence primordium on the growing point (L-LEAF, the true guide for determining the inflorescence position), the L-LEAFs of ‘My Lock’ plants in all growth periods and ‘House Momotaro’, ‘Momotaro 8’, and ‘Super Fast’ plants in the non-high-temperature growth periods were always just above the inflorescences, that is, the LEAF-BIs were always the leaves below the L-LEAFs. In contrast, the L-LEAFs of all cultivars except ʻMy Lockʼ in the high-temperature growth periods were often just below the inflorescence, that is, the LEAF-BIs were often the L-LEAFs. Comparing the leaf-number of LEAF-BI and that of L-LEAF demonstrated that the former often overestimated the inflorescence positon among growth periods and cultivars. In temperature treatments with ‘House Momotaro’, such a positional switch of the L-LEAF was reproducible. External observation indicated that the stem on the L-LEAF side and the stem on the inflorescence side extended non-uniformly and the position of the L-LEAF was determined by which side extended faster. Collectively, the LEAF-BI is not a leaf identified morphogenetically, and to identify the position of the inflorescence, the leaf-number of L-LEAF, not LEAF-BI, should be used.
Tomato inflorescence develops on the stem after the predetermined number of leaves, which varies according to environmental conditions, expand successively. The position of inflorescences, especially the first inflorescence, on the stem is important in deciding the timing of anthesis (Kinet and Peet, 1997; Wittwer and Teubner, 1956). The position of inflorescences is influenced by air temperature (Calvert, 1957; Phatak et al., 1966; Wittwer and Teubner, 1956, 1957), day length, cultivar (Wittwer, 1963; Wittwer and Teubner, 1956), and treatment with gibberellin-related substances (Wittwer and Tolbert, 1960). In these previous studies, the leaf-number (ordinal number from the oldest leaf) of the leaf just below the inflorescence (LEAF-BI) was considered to be an indicator of the position of the inflorescence and was determined when the extension of the stem near the inflorescence was mostly complete.
Light microscopic observation showed that the inflorescence is formed following the differentiation of a certain number of leaves at the growing point (Calvert, 1965). Therefore, the leaf-number of the last initiated leaf before inflorescence primordium (L-LEAF), is the inflorescence position in morphogenesis.
It was observed in commercial growers’ greenhouses by the authors that the LEAF-BI can be either the L-LEAF or the leaf just below the L-LEAF, depending on the temperature conditions. If true, the leaf-number of LEAF-BI would not be a suitable indicator. An appropriate evaluation of the inflorescence position may contribute to the development of tomato plants on which the leaf-number of L-LEAF is low, by breeding, cultivar selection, and environmental control during raising of the seedlings. Therefore, tomatoes were grown under different temperature conditions to measure the L-LEAF and LEAF-BI leaf-numbers and the vertical positional relationship, which was numerically expressed, between the inflorescence and L-LEAF, and the causes of changes in the vertical positional relationship between them, was investigated.
In Expt. 1, seeds of tomato cultivars ‘House Momotaro’, ʻMomotaro 8ʼ (Takii & Co., Kyoto, Japan), ʻMy Lockʼ (Sakata Seed Corp., Kanagawa, Japan), and ‘Super Fast’ (Aisan Seed Co., Ltd., Aichi, Japan, popular in Japan) were sown bimonthly between Oct. 23, 2008 and Aug. 23, 2010 in quadrant 128 cell trays (Landmark Plastics Corp., Akron, OH, USA) filled with Yosaku N-150 soil (N:P:K = 150:437:125 mg·L−1; JCAM Agri Co., Tokyo, Japan) and grown in our university’s greenhouse (Atsugi, Japan) equipped with a ventilation fan (higher than 25°C) and a heater (lower than 14°C). For example, cultivation of seeds sown on Oct. 23, 2008 is referred to as Oct. 2008 growth. At the three- or four-leaf stage, seedlings were potted in 7.5 cm diameter plastic pots filled with Kureha horticultural compost (N:P:K = 0.4:0.8:0.5 g·kg−1, Kureha Corp., Tokyo, Japan. The same compost was used in subsequent procedures and the compost contained enough nutrients for normal plant growth in these experiments) and at the seven- or eight-leaf stage plants were repotted in 10.5 cm diameter plastic pots. When the first inflorescence started anthesis in approximately 50% of all seedlings, the seedlings were transferred to 24 cm diameter plastic pots and grown using the single stem training method. In all growth periods, 60 pots (15 pots per cultivar) were arranged in 3 lines in an alternate order. However, due to disease during growth, the number of seedlings was reduced to 12 to 15 per cultivar.
When the fifth inflorescence started anthesis in approximately 50% of all seedlings (at 66 to 119 days after sowing), the leaf-numbers of L-LEAF and LEAF-BI and the inflorescence position indexes (described below) of the first, second, and third inflorescences were determined. According to Calvert (1965) and Schmitz and Theres (1999), the axillary bud formed on the axil of the L-LEAF following inflorescence differentiation grows straight upwards, pushing through the inflorescence, and the L-LEAF in the opposite direction. Also, following the extension of the axillary bud of the L-LEAF, another axillary bud is formed on the axil of the leaf just below the L-LEAF, extending as vigorously. Using this knowledge, the L-LEAF can be identified. In Figure 1, the L-LEAF is positioned above the inflorescence (inferior inflorescence) in the left example and is positioned below the inflorescence (superior inflorescence) in the right example. In the example shown on the left in Figure 1, the inflorescence position index (IPI) was calculated as −100 × a/b (a: distance between the base of the L-LEAF and the base of the inflorescence, b: internode distance between the L-LEAF and the leaf just below the L-LEAF, the negative sign means that the inflorescence is positioned below). In the example shown on the right, the IPI was calculated as 100 × c/d (c: distance between the base of the L-LEAF and the base of the inflorescence, d: internode distance between the L-LEAF and the leaf just above the L-LEAF).
Schematic diagram of the positional relationship between the inflorescence and the last initiated leaf before inflorescence primordium (L-LEAF). IPI = inflorescence position index; a, b, c, and d = length between illustrated points.
Changes in average daily air temperature recorded at 1.5 m above the ground of the greenhouse by a resistance thermometer (mean of the daily maximum and minimum air temperatures for the period between sowing and the start of third inflorescenceʼs anthesis, when the distance between the first, second, or third inflorescences and the adjacent leaves became fixed) during the growth periods are shown in Figure 2. Based on the average daily air temperature changes, the Oct. 2008, Dec. 2008, Feb. 2009, Oct. 2009, Dec. 2009, and Feb. 2010 growth periods were classified as low-temperature periods (mean of average daily air temperatures, 18.9°C to 20.2°C), the Apr. 2009, Aug. 2009, and Apr. 2010 growth periods were classified as intermediate-temperature growth periods (mean of average daily air temperatures, 23.0°C to 23.6°C) and the June 2009, June 2010, and Aug. 2010 growth periods were classified as high-temperature growth periods (mean of average daily air temperatures, 26.3°C to 29.7°C).
Average daily temperature during growth periods in a greenhouse (Expt. 1). Bars show periods from sowing (the month names are indicated above or below bars) to the start of anthesis in the third inflorescence.
Inside the greenhouse used for Expt. 1, 4 small plastic houses (area: 1.2 × 1.5 m, height 1.5 m) made with transparent polyethylene film were set up in a square configuration. Two plastic houses diagonally across from each other were assigned to either the non-high-temperature treatment or the high-temperature treatment (Expt. 2). The high-temperature plastic houses were equipped with electric heaters for horticulture (500 W, set at 30°C) and the non-high-temperature plastic houses had ventilation holes on the northern side where sunlight did not come in. On May 5 and Nov. 15, 2011, seeds of ʻHouse Momotaroʼ were sown according to Expt. 1 and, after being kept in non-high-temperature houses, half of the quadrant cell trays were transferred to high-temperature houses when the cotyledons started unfolding. The seedlings (12 seedlings per plastic house) were potted in 18 cm plastic pots when the first inflorescences started anthesis. When the third inflorescences started anthesis, IPI was determined for the first inflorescences. Means of average daily air temperatures after the start of temperature treatment were 24.3°C and 30.1°C in the non-high- and high-temperature treatments, respectively, in the May 2011 growth and, 18.7°C and 26.4°C in the non-high- and high-temperature treatments, respectively, in the Nov. 2011 growth.
Effects of temperature treatment and growth period on the widening of the distance between the inflorescence and the L-LEAFIn Expt. 3, the progress of distance widening between the base of the inflorescence and the base of the L-LEAF was examined. According to Expt. 2, seeds of ʻHouse Momotaroʼ were sown on Feb. 8, 2012 and their seedlings were grown in the non-high- and high-temperature plastic houses (12 seedlings per group). The distance between the leaf just below the L-LEAF and the inflorescence and the distance between the leaf just below the L-LEAF and the L-LEAF were measured using a vernier caliper from 33 and 73 days after the start of treatment for the non-high- and high-temperature groups, respectively. The means of the average daily air temperatures after the start of temperature control were 19.6°C for the non-high-temperature group and 30.0°C for the high-temperature group.
On Apr. 23 and July 10 in 2011, ʻHouse Momotaroʼ seeds were sown in 4 quadrant cell trays in a greenhouse and 128 seedlings were obtained (Expt. 4). When the axillary bud formed on the axil of the L-LEAF grew to 1 to 2 cm (at 36 days after sowing in the Apr. 2011 growth and at 33 days after sowing in the July 2011 growth), a horizontal incision was made on the stem using a surgical needle in a straight line connecting the bases of the inflorescence, axillary bud and L-LEAF. The scar left by the incision was then used to follow stem elongation in this region. The scar was observed on the first day of anthesis of the third inflorescence (60 days after sowing in both groups). The means of the average daily air temperatures were 21.9°C for the Apr. 2011 growth and 28.9°C for the July 2011 growth.
Statistical analysisFor Expt. 1, the difference among 12 growth periods for each cultivar and differences among 4 cultivars in each growth period were analyzed by analysis of variance (n = 12 to 15). The relation between IPIs of the first, second, and third inflorescences and air temperature in each period was determined using data for each plant and the mean value of average daily air temperature. For Expt. 2, differences in mean values for the two treatments was analyzed using the t-test (n = 24). For Expt. 3, differences in mean values for 9 and 12 measurements were analyzed using Tukey’s studentized range test (n = 12).
ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, ʻMy Lockʼ, and ‘Super Fast’ were grown in a greenhouse in 12 growth periods (Expt. 1). The effect of growth period on each of the IPIs, leaf-numbers of L-LEAF, and those of LEAF-BI for the first, second, and third inflorescences was significant in each cultivar (P < 0.001). The effect of cultivar on each of them for the first, second, and third inflorescences was also significant in each growth period (P < 0.01, except for the leaf-numbers of L-LEAF and LEAF-BI in Apr. 2010: P < 0.05).
In 4 cultivars, the leaf-numbers of LEAF-BI (Fig. 3) of the first inflorescence (LEAF-BI-1) were 8.3 to 11.7 in high-temperature periods and 6.1 to 9.2 in low-temperature periods. These leaf-numbers in intermediate-temperature periods were intermediate between those in high- and low-temperature periods. The leaf-numbers of LEAF-BI of the second (LEAF-BI-2, Fig. 4) and third (LEAF-BI-3, Fig. 5) inflorescences were also higher in high-temperature periods than in low-temperature periods. Wittwer and Teubner (1956) reported that the leaf-number of LEAF-BI-1 was 8.6 at 21°C, but 6.9 at 10°C. An increase in the leaf-number when grown at high temperature was also reported by Calvert (1957), Wittwer and Teubner (1957), and Phatak et al. (1966).
Effect of growing period on the position of the first inflorescence in 4 cultivars in a greenhouse (Expt. 1). Effect of growth period in each cultivar and effect of cultivar in each growth period were significant (P < 0.05). #L-LEAF = leaf-number of the last initiated leaf before the inflorescence primordium. #LEAF-BI = leaf-number of the leaf just below the inflorescence. IPI = inflorescence position index explained in Figure 1. HM = ʻHouse Momotaroʼ. M8 = ʻMomotaro 8ʼ. ML = ʻMy Lockʼ. SF = ‘Super Fast’.
Effect of growing period on the position of the second inflorescence in 4 cultivars in a greenhouse (Expt. 1). Effect of growth period in each cultivar and effect of cultivar in each growth period were significant (P < 0.05). #L-LEAF = leaf-number of the last initiated leaf before the inflorescence primordium. #LEAF-BI = leaf-number of the leaf just below the inflorescence. IPI = inflorescence position index explained in Figure 1. HM = ʻHouse Momotaroʼ. M8 = ʻMomotaro 8ʼ. ML = ʻMy Lockʼ. SF = ‘Super Fast’.
Effect of growing period on the position of the third inflorescence in 4 cultivars in a greenhouse (Expt. 1). Effect of growth period in each cultivar and effect of cultivar in each growth period were significant (P < 0.05). #L-LEAF = leaf-number of the last initiated leaf before the inflorescence primordium. #LEAF-BI = leaf-number of the leaf just below the inflorescence. IPI = inflorescence position index explained in Figure 1. HM = ʻHouse Momotaroʼ. M8 = ʻMomotaro 8ʼ. ML = ʻMy Lockʼ. SF = ‘Super Fast’.
In regard to the cultivar difference, LEAF-BIs were high for ‘Super Fast’ and low for ʻMy Lockʼ in most growth periods. For example, in the Aug. 2010 growth period when the cultivar difference was largest, LEAF-BI-1, 2, and 3 were 11.7, 15.6, and 19.1 for ‘Super Fast’, and 8.7, 11.5, and 14.4 for ʻMy Lockʼ, respectively. Wittwer (1963) and Wittwer and Teubner (1956) also reported a cultivar difference in LEAF-BI-1.
L-LEAF is the true indicator of the inflorescence position in morphogenesis. After extension of the stem near the inflorescence, the L-LEAF is near the inflorescence and extending in the direction opposite to the inflorescence. The leaf-numbers of L-LEAF of the first, second, and third inflorescence (L-LEAF-1, 2, and 3, respectively) of 4 cultivars were also high in high-temperature periods, low in low-temperature periods, and intermediate in intermediate-temperature periods. Overall, the leaf-numbers of L-LEAF-1 (Fig. 3) were between 7.1 and 12.6, consistent with the micrographic findings by Heuvelink (2005) and Schmitz and Theres (1999), who reported that after 7 to 11 leaves have initiated at the growing point, the first inflorescence is formed.
The differences in leaf-number between L-LEAF-1 (Fig. 3) and L-LEAF-2 (Fig. 4) of 4 cultivars were 2.7 (ʻMomotaro 8ʼ, June 2010) to 4.5 (‘Super Fast’, June 2009), and the differences in leaf-number between L-LEAF-2 and L-LEAF-3 (Fig. 5) were 2.6 (ʻHouse Momotaroʼ, June 2010) to 3.9 (‘Super Fast’, June 2009), fluctuating by growth period. Atherton and Harrisʼs (1986) and Schmitz and Theresʼs (1999) findings that the second and subsequent inflorescences were formed at the growing points following the differentiation of 3 leaves are consistent with our results.
The leaf-numbers of L-LEAFs were 1 more than those of LEAF-BIs in many growth periods. However, in the June 2009 growth period the number of L-LEAF-1 (Fig. 3) of ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’, were identical or near to those of LEAF-BI-1. A similar phenomenon occurred for the second inflorescence (Fig. 4) in the June 2009 growth period for ʻHouse Momotaroʼ and ‘Super Fast’, in the June 2010 growth period for ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’ and in the Aug. 2010 growth period for ‘Super Fast’. The phenomenon also occurred for the third inflorescence (Fig. 5), in the June 2009 growth period for ‘Super Fast’ and in the June 2010 and Aug. 2010 growth periods for ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’.
The leaf-numbers of L-LEAF-1 and LEAF-BI-1 of ʻHouse Momotaroʼ were 7.8 and 6.9 in the Oct. 2008 growth period, and 10.7 and 10.7 in the June 2009 growth period, respectively. The increase in the leaf-number of LEAF-BI-1 (55%) was more than that of L-LEAF-1 (37%). The numbers of LEAF-BI-1 of ʻMomotaro 8ʼ and ‘Super Fast’ also changed more than those that of L-LEAF-1 between these periods. Furthermore, in the June 2009 growth period, the leaf-numbers of L-LEAF-1 for ‘Super Fast’, ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ʻMy Lockʼ were 11.0, 10.7, 10.5, and 9.8, and those of LEAF-BI-1 were 11.0, 10.7, 10.2, and 8.8, respectively, showing that the leaf-number of LEAF-BI was affected by cultivar more than that of LEAF-BI. Similar results were obtained for their second and third inflorescences. Collectively, the leaf-numbers of LEAF-BIs varied more among growth periods and cultivars than those of L-LEAFs.
IPI was calculated to estimate the vertical positional relationship between the inflorescence and L-LEAF quantitatively. IPIs for the first (Fig. 3), second (Fig. 4), and third (Fig. 5) inflorescences were negative values (inferior inflorescence, see the left panel in Fig. 1) in many of the growth periods for ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’ and in all growing periods for ʻMy Lockʼ. These results corresponded to previous findings that revealed after inflorescence differentiation, with the extension of the axillary bud formed on the axil of the L-LEAF, the L-LEAF gradually moves to a position above the inflorescence (Calvert, 1965; Heuvelink, 2005; Schmitz and Theres, 1999).
On the other hand, in the June 2009 growth period, IPIs for the first and second inflorescences of ʻHouse Momotaroʼ, the first inflorescence of ʻMomotaro 8ʼ and the first, second, and third inflorescences of ‘Super Fast’ were positive values (superior inflorescence, see the right panel in Fig. 1). Also, in the June 2010 growth period, IPIs for the second and third inflorescences of ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’ and in the Aug. 2010 growth period, IPIs for the third inflorescence of ʻHouse Momotaroʼ and ʻMomotaro 8ʼ and the second and third inflorescences of ‘Super Fast’ were positive values.
The June 2009, June 2010, and Aug. 2010 growth periods were high-temperature periods (Fig. 2), suggesting that superior inflorescence occurs at high air temperatures. The mean of average daily air temperatures for each growth period and IPIs for the first, second, and third inflorescences for ʻHouse Momotaroʼ plants had a significantly positive correlation (Fig. 6). This was also the case with the first, second, and third inflorescences for ʻMomotaro 8ʼ (r = 0.467, 0.755, and 0.840, data not shown) and ‘Super Fast’ (r = 0.416, 0.762, and 0.850, data not shown). A significant (P < 0.001) positive correlation was also found in the first, second, and third inflorescences for ʻMy Lockʼ (r = 0.369, 0.607, and 0.717, data not shown), which always had inferior inflorescences.
Correlation between air temperature during the growth period and inflorescence position index explained in Figure 1 in ‘House Momotaro’ plants in a greenhouse (Expt. 1). Means during each growth period are plotted.
Concerning the cultivar difference, the IPI of the first inflorescence (Fig. 3) was high for ʻHouse Momotaroʼ and low for ʻMy Lockʼ, and IPIs of the second (Fig. 4) and third (Fig. 5) inflorescence were high for ‘Super Fast’ and low for ʻMy Lockʼ in many or all growth periods.
Effect of temperature treatment on the positions of the inflorescence and the L-LEAFIn Expt. 2, ʻHouse Momotaroʼ seedlings were grown at non-high and high temperatures and the position of the first inflorescence was investigated. The IPI for the first inflorescence (Fig. 7) in the May 2011 and Nov. 2011 growths were −27.5% and −19.5% in the non-high-temperature group (i.e., inferior inflorescence) and 33.9% and 30.2% in the high-temperature group (i.e., superior inflorescence). Therefore, the suggestion made in Expt. 1 that the switch from inferior to superior inflorescence is caused by high temperature was confirmed.
Effect of air temperature treatment on the first inflorescence position index explained in Figure 1 in ‘House Momotaro’ plants (Expt. 2). Vertical bar indicates SE. Asterisk indicates significant difference between treatments (P < 0.05).
As described above, for ʻHouse Momotaroʼ, ʻMomotaro 8ʼ, and ‘Super Fast’, the leaf-number of L-LEAF-1 was frequently 1 more than that of LEAF-BI-1 and often nearly identical to that of LEAF-BI-1 in non-high-temperature and high-temperature growth periods, respectively (Fig. 3). This was based on the fact that in non-high-temperature growth periods, the inflorescence was between the L-LEAF-1 and the LEAF-BI-1, and in high-temperature growth periods, the L-LEAF-1 was below the inflorescence, based on data concerning IPI. This is because, in non-high-temperature growth periods, the leaf-numbers of the LEAF-BI-1 and L-LEAF-1 were lower than in high-temperature growth periods and the LEAF-BI-1 was frequently below the L-LEAF-1, so the evaluation of the leaf-number of LEAF-BI-1 overestimated the inflorescence position between non-high- and high-temperature growth periods. A similar explanation is proposed for the overestimation generated by the leaf-number of LEAF-BI-1 among different cultivars.
Such a positional switch in inflorescence between different temperatures has not been reported. McAvoy and Janes (1990) reported that the first inflorescence was positioned above the L-LEAF in some treatments, but failed to identify the causes.
Effects of temperature treatment and growth period on the widening of the distance between the inflorescence and the L-LEAFIn Expt. 3, the widening of the distance between the first inflorescence and the L-LEAF of ʻHouse Momotaroʼ was compared between the non-high- and high-temperature groups. As shown in Figure 8, in the non-high-temperature group, the L-LEAF was higher 46 days after the start of temperature treatment than that of the inflorescence and L-LEAF reached 61 mm above the inflorescence on day 55. On the other hand, in the high-temperature group, the height of the inflorescence was higher on day 42 than that of L-LEAF, and the inflorescence was 21 mm above the L-LEAF on day 45. These results suggest that stem growth, which is faster on the inflorescence side or the L-LEAF side opposite to the inflorescence side, is controlled by air temperature. Expt. 4 was conducted to further confirm this possibility.
Effect of air temperature treatment on the widening of the distance between the first inflorescence and the last initiated leaf before the first inflorescence primordium (L-LEAF) in ‘House Momotaro’ sown in Feb. 2012 (Expt. 3). Positive values mean that the inflorescence is positioned above L-LEAF and negative values mean that the inflorescence is positioned below L-LEAF. Means with the same letter within each treatment are not significantly different at P < 0.05.
In Expt. 4, the scar development process was clearly observable in 3 plants in the Apr. 2011 growth (non-high-temperature). When viewed from an angle with the first inflorescence on the left and the L-LEAF on the right, the scar ran obliquely upward from the base of the first (inferior) inflorescence to the base of the L-LEAF (Fig. 9). On the other hand, in the July 2011 growth (high-temperature), the scar was clearly observable in 4 plants. It ran obliquely upward from the base of the L-LEAF to the base of the first (superior) inflorescence. These results indicate that as the axillary shoot that initiated in the axil of the L-LEAF grew vertically, the stem on the L-LEAF side extended predominantly at non-high temperature and the stem on the inflorescence side extended predominantly at high temperature.
Scar development on the stem between the first inflorescence (I) and last initiated leaf (L) before the first inflorescence primordium of ʻHouse Momotaroʼ plants in non-high-(left, sowing in Apr. 2011) and high-temperature (right, sowing in July 2011) growth periods in a greenhouse (Expt. 4).
In our experiments, the L-LEAFs (identified morphogenetically) of ‘House Momotaro’, ‘Momotaro 8’, and ‘Super Fast’ were always just above the inflorescence under non-high temperature conditions (the LEAF-BIs designated conventionally as a guide for determining the inflorescence position were the leaf just below the L-LEAF), but were often just below the inflorescence under high temperature conditions (the LEAF-BIs were the L-LEAF), meaning that morphogenetically different leaves can considered to be LEAF-BIs. The evaluation of the leaf-number of LEAF-BI overestimated the inflorescence position among some growth periods and cultivars. Therefore, to compare the position of inflorescence among treatments, the L-LEAF should be used as a guide.
We sincerely thank Aki Kato, Kensuke Kurahashi, Akihiro Yoshida, Yusuke Umeda, Shiori Onda, Kazumasa Nakamura, Naoto Gunji, and Makoto Nowatari for their cooperation in this experiment.
