Agricultural and Forest Meteorology 100 2000 213–230
A model to estimate the temperature of a maize apex from meteorological data
Lydie Guilioni
a
, Pierre Cellier
b,∗
, Françoise Ruget
c
, Bernard Nicoullaud
d
, Raymond Bonhomme
b
a
Laboratoire d’ Ecophysiologie des Plantes sous Stress Environnementaux, INRA-AGRO.M, UFR Agronomie et Bioclimatologie, 2, place Viala, 34060 Montpellier Cedex 02, France
b
INRA, Unité de Recherche en Bioclimatologie, F78850 Thiverval-Grignon, France
c
INRA, Unité de Recherche en Bioclimatologie, 84914 Avignon Cedex 9, France
d
INRA, Service d’Etude des Sols et de la Carte Pédologique de France, Ardon, 45160 Olivet, France Received 16 September 1998; received in revised form 23 July 1999; accepted 17 September 1999
Abstract
During early growth, when the apical meristem of a maize plant is close to the soil surface, its temperature may be very different from air temperature. A model is proposed to estimate apex temperature from meteorological data, when the leaf
area index is less than 0.5. This model is based on the energy balance of the apical meristem, considered as a vertical cylinder close to the soil surface, called ‘apex’. Soil surface temperature was calculated from an energy and water balance of the
soil. Input data were hourly standard meteorological data and soil texture. Stomatal conductance was calculated from solar radiation and water vapor deficit.
Five field experiments with different soil and climatic conditions were conducted to calibrate and validate the model. The roughness length of the soil surface was used as a calibrating factor. The selected value was 0.3 mm, and was used on all
datasets. The agreement between observed and calculated apex temperatures was fairly good, with residual standard deviations between 0.8 and 1.9 K in five experiments, while apex temperature was generally higher than air temperature at screen level
by more than 5–7 K during the day. This study showed that the main problem to overcome in estimating apex temperature, is to calculate air temperature at apex height, i.e. at several centimeters from the soil surface. This requires development of
precise soil surface temperature models. ©2000 Elsevier Science B.V. All rights reserved.
Keywords: Maize; Meristematic zone; Temperature; Prediction; Energy balance; Meteorological data
1. Introduction
Temperature has a major influence on plant growth and particularly on development rates. Many studies
have shown that leaf initiation, leaf appearance and elongation are strongly related to temperature Watts,
∗
Corresponding author. Tel.: +33-1-30-81-55-55; fax: +33-1-30-81-55-63.
E-mail address: cellierbcgn.grignon.inra.fr P. Cellier.
1972a; Warrington and Kanemasu, 1983 in maize; Gallagher, 1979 in wheat and barley; Ong, 1983 in
pearl millet. De Reaumur first suggested in 1735 De Reaumur, 1735 that the duration of particular stages
of growth was directly related to temperature and that this duration for a particular species could be pre-
dicted using the sum of mean daily air temperature. This way of normalizing time with temperature, the
thermal time, in order to predict the plant development rates has been widely used in this century Durand
0168-192300 – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 1 9 2 3 9 9 0 0 1 3 0 - 6
214 L. Guilioni et al. Agricultural and Forest Meteorology 100 2000 213–230
et al., 1982; Ritchie and NeSmith, 1991. The concept of thermal time assumes a strong correlation between
air temperature and that sensed by the plant Durand et al., 1982. But in maize, like in many monocot crop
plants, the specific locations where temperature influ- ences development — i.e. the zones where cell divi-
sion and expansion are occurring Kleinendorst and Brouwer, 1970; Watts, 1972b; Peacock, 1975 — are
close to the soil surface during early growth. In these conditions, the development rates leaf initiation, leaf
appearance or reproductive initiation rate are not ac- curately related to air temperature Beauchamp and
Lathwell, 1966; Brouwer et al., 1970; Aston, 1987. Duburcq et al. 1983 have shown that the develop-
ment rate of maize until male floral initiation was bet- ter related to soil temperature than to air temperature.
Swan et al. 1987 found that the development rate of maize was best described using soil temperature until
the sixth leaf was fully developed. More recently, Shar- ratt 1991 over barley and Bollero et al. 1996 over
maize observed different development rates under dif- ferent controlled soil temperatures. Moreover, looking
directly at plant temperature, either in growth-chamber or in field conditions, Ben Haj Salah and Tardieu
1996 observed that leaf elongation rate was corre- lated better with meristematic apex temperature than
with air temperature. Similarly, Jamieson et al. 1995 calculated thermal time based on plant temperature.
They concluded that ‘a model of leaf appearance based on near surface temperature and canopy temperature
gave superior prediction than others based on air tem- perature’.
Cellier et al. 1993 have shown that the tempera- ture of the meristem was significantly different from
both air and soil surface temperatures. The differences between air temperature at screen height and meris-
tem temperature reached almost 6 K for a daytime average, which means that hourly values were much
larger. Thus, accounting for the influence of tempera- ture on growth and development should be improved
by using the actual temperature of the extension zones. Beauchamp and Torrance 1969 proposed a model for
estimating the internal temperature of a young maize plant. The maize stem was represented as a vertical
cylindrical bar with one end in the soil considered as an infinite source of heat. This model overestimated
the temperature of the plant certainly because neither the circulation of water in the stem nor the transpi-
ration was considered. Cellier et al. 1993 proposed a model — based on a energy balance equation —
to predict the differences between air and meristem temperatures from standard meteorological data dur-
ing the early growth of a maize plant. However, this model presented some limits. The radiation balance
neglected the shade of leaves, and in the absence of any references, the stomatal conductance of the meris-
tematic zones was a fitting parameter. Furthermore, the output data are averages of day and night temperatures
with no way to estimate maximum or minimum which may be the most relevant temperatures for explaining
differences in development rate Weaich et al., 1996.
In this paper, we proposed a model based also on an energy balance approach, for estimating the temper-
ature of the extension zones of a young maize. This model works at hourly time steps, from standard me-
teorological data. The main improvements compared to the original model of Cellier et al. 1993 are related
to the radiation balance, the stomatal conductance pa- rameterization and the air temperature profile near the
soil surface.
2. Methods
