Influence of photoperiod and air temperature on the growth, flowering and maturation of soybean (Glycine max (L.) Merrill)

Influência do fotoperíodo e da temperatura do ar no crescimento, floração e maturação da soja (Glycine max (L.) Merrill)

ARTICLES

Influence of photoperiod and air temperature on the growth, flowering and maturation of soybean (Glycine max (L.) Merrill)¹

Influência do fotoperíodo e da temperatura do ar no crescimento, floração e maturação da soja (Glycine max (L.) Merrill)

G.M.S. Câmara^I; T. Sediyama^II; D. Dourado-Neto^{II, II}; M.S. Bernardes^II

^IDepto. de Agricultura-ESALQ/USP, C.P. 9, CEP: 13418-900 - Piracicaba, SP-Brazil

^IIDepto. de Agricultura-UFV, C.P. 365, CEP: 36560-000 - Viçosa, MG-Brazil

^IIBolsita do CNPq

ABSTRACT

With the purpose to evaluate the effect of short (12 hours) and long (13 and 14 hours) photoperiods and air temperature regimes (winter and summer growing seasons) on soybean behaviour, greenhouse experiments were installed at the Federal University of Viçosa, Brasil, from June 1984 to December 1985. In each experiment, under a completely randomized design with 12 treatments (soybean cultivars) and eight replicates: duration of vegetative period from emergency to stage R1 or flowering (DVP, in days); plant height (PH, m); number of nodes per plant at stage R1 (NNP); and duration of soybean cycle from emergency to stage R7 or physiological maturity point (DC, days), were evaluated. The results permit to conclude that: the vegetative period from emergency to flowering and the juvenile period are significantly affected by the photoperiod and temperature differences; shorter photoperiods or higher temperatures anticipate flowering; longer photoperiods under the same temperature regime or higher temperature under the same photoperiod regime result in higher plants.

Keywords: phenology, plant height, photoperiodism

RESUMO

Experimentos em casa-de-vegetacão visando estudar o comportamento de cultivares de soja perante fotoperíodo curto (12 horas) e longo (13 e 14 horas) e na presença de temperaturas variáveis em função de diferentes épocas de semeadura, foram instalados na Universidade Federal de Viçosa, MG, Brasil, durante o período de junho de 1984 a dezembro de 1985. Delineado inteiramente ao acaso, cada experimento contou com doze cultivares de soja repetidos oito vezes por época. Avaliaram-se as seguintes características: duração do subperíodo emergência - inicio do florescimento, altura de planta e número de nós vegetativos formados por planta e duração do subperíodo emergencia - maturidade fisiológica. Concluiu-se que a fase fenológica da soja compreendida entre a emergência e o inicio do florescimento é significativamente influenciada pelas variações do fotoperíodo e da temperatura do ar; fotoperíodo e temperatura interferem com a duração fenológica do período juvenil da soja e acréscimos de fotoperíodo e de temperatura antecipam o florescimento da soja e aumentam a altura de suas plantas.

Descritores: fenologia, altura de planta, fotoperiodismo

INTRODUCTION

The photoperiod is defined as the time, within 24 hours of the terrestrial day, when there is light or sun bright (Ometto, 1981) also called daylength and defined as the time in hours between sunrise and sunset (Goudriaan & van Laar, 1994). Daylength, temperature and rainfall are the most important climatic factors to select a region for soybean cultivation and production (Câmara, 1991).

Latitude determines the daylength pattern. In soybean, a short-day plant, daylength affects the development rate from emergence to flower induction and particularly determines the time necessary for flowering (Marcos Filho et al., s/d; Câmara, 1992). In what concerns the air temperature, it is well known that higher temperatures during the growing season favor faster development rates of this crop and reduce time for flowering (Major et al., 1975a; Major et al., 1975b; Miyasaka & Medina, 1970).

Literature about the correlation between photoperiodic and temperature effects on soybean development is scarce. The objective of the present study was to evaluate the effects of these two climatic factors on growth and time for flowering and grain maturation of some soybean cultivars.

MATERIAL AND METHODS

Greenhouse experiments were installed at Federal University of Viçosa, state of Minas Gerais, Brazil (Latitude: 20° 45' South. Longitude: 42º 51' West. Altitude: 650 m). The experiments were conducted using twelve Brazilian cultivated varieties: Cristalina, Doko, IAC-6, IAC-7, IAC-8, Paraná, Primavera, Savana, Tropical, UFV-1, UFV-4, and UFV-5 (Sediyama et al., 1981). The following combinations of growing period and photoperiod were studied:

- Winter season-1984: from June 18, 1984 until December 4, 1984 with short-days (photoperiod = 12 hours) and long-days (photoperiod = 13 hours).

- Summer season-1984/1985: from December 14, 1984 until May 26, 1985 with short-days (photoperiod = 12 hours) and long-days (photoperiod = 13 hours).

- Winter season-1985: from July 17, 1985 until December 23, 1985 with short-days (photoperiod = 12 hours) and long-days (photoperiod = 14 hours).

The daylength of 12, 13 and 14 hours were used to simulate the natural photoperiodic conditions comparable to those of the Brazilian soybean growing regions of the Equator (Latitude=0°), and of the summer solstice in tropical latitudes of the central high-plains (Latitude=15° to 19° S) and of the South States (Latitude=30º to 32°S), respectively. The three photoperiods were kept constant inside of the greenhouses, during the entire growing season, by artificial lights. Sowing the crop in different seasons allowed to evaluate the effect of three different temperature regimes. Daily maximum and minimum temperature were monitored in all greenhouses during the three growing seasons.

We adopted for each photoperiod and growing season a completely randomized experimental design with 12 treatments (soybean cultivars) in eight replicates. Each replicate was represented by a pot with 3 kg of soil with two soybean plants. To compare the effect of different photoperiod within the same growing season or the temperature effect of different growing seasons with the same photoperiod, we adopted statistical analysis techniques for group of experiments. Significant differences were evaluated with test of Tukey at 5% probability level.

The phenological staging scale of Fehr & Caviness (1977) reviewed by Ritchie et al. (1994) was adopted to estimate: duration of vegetative period from emergency to stage R1 or flowering (DVP, in days); plant height (PH, m); number of nodes per plant at stage R1 (NNP); and duration of soybean cycle from emergency to stage R7 or physiological maturity point (DC, days).

RESULTS AND DISCUSSION

Long-day conditions of 13 and 14 hours daylength extended DVP, for al cultivars in every growing season, in average 28.6% to 48.8% in comparison to short-day conditions of 12 hours daylength (TABLES 1, 2 and 3). As a result of a larger vegetative period, soybean plants were higher (42.4% to 103%) and presented a larger number of nodes (33.8% to 57.3%). The duration of soybean cycle (DC) was also extended in average 2.3% to 4% under long-day conditions, although not as much as for the vegetative period.

Since the temperature in the same growing season was not significantly different between both daylength conditions, the extension the vegetative period under longer days was consequence of the daylength itself. Thus, the critical daylength at which flower formation is initiated varies according to photoperiodic conditions during juvenile phase or are dependent of the plant size.

The differences between the largest and lowest values of mean square error permitted to compare the results of the first and second growing season, to evaluate the temperature effect (TABLES 4 and 5).

The duration of vegetative period was reduced from the winter to the summer growing seasons, independently of photoperiodic conditions. The enhancement of development rate reducing the juvenile period and anticipating flowering under summer growing season was probably result of the warmer temperatures. Despite the shorter juvenile and vegetative periods of summer growing season compared to winter growing seasons, higher temperatures favored growth of soybean resulting in higher plants in summer.

Under 12 hours daylength conditions during the first (Winter season 1984) and second (Summer 1984/1985) growing season, the average for the maximum, minimum and daily average temperature were 31.8°C, 15.0°C and 23.4°C, and 33.1°C, 22.1°C e 27.6°C. respectively. The differences between growing seasons for vegetative period and daily average temperature were 22.6 days and 4.2°C. The ration of both values indicates that a increase in 1.0°C resulted in 5.4 days anticipation for flowering under short-day conditions.

Under 13 hours daylength conditions during the first (Winter season 1984) and second (Summer 1984/1985) growing season, the average for the maximum, minimum and daily average temperature were 31.0°C, 15.2°C and 23.1°C, and 34.0°C, 22.3°C e 28.2°C. respectively. The differences between growing seasons for vegetative period and daily average temperature were 20.4 days and 5.1°C. The ration of both values indicates that a increase in 1.0°C resulted in 4 days anticipation for flowe-ring under short-day conditions (12 hours).

CONCLUSIONS

- The vegetative period from emergency to flowering and the juvenile period are significantly affected by the photoperiod and temperature differences. Shorter photoperiods or higher temperatures anticipate flowering.

- Longer photoperiods under the same temperature regime or higher temperature under the same photoperiod regime result in higher plants.

Recebido para publicação em 15.04.97

Aceito para publicação em 18.05.97

Presented at 4th Congress of the European Society for Agronomy, 7-11 July, 1996. Veldhoven-Wageningen. The Netherlands

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Publication Dates

• Publication in this collection
  31 May 2005
• Date of issue
  June 1997

History

• Accepted
  18 May 1997
• Received
  15 Apr 1997