Journal Article

Variability of Phyllochron, Plastochron and Rate of Increase in Height in Photoperiod-sensitive <i>Sorghum</i> Varieties

B. Clerget, M. Dingkuhn, E. Gozé, H. F. W. Rattunde and B. Ney

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 101, issue 4, pages 579-594
Published in print March 2008 | ISSN: 0305-7364
Published online January 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcm327
Variability of Phyllochron, Plastochron and Rate of Increase in Height in Photoperiod-sensitive Sorghum Varieties

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

West African sorghum (Sorghum bicolor) varieties are generally highly photoperiod-sensitive, which is a necessary adaptation to the variable onset date of the rainy season and the variable dates of sowing in the savannah zone. Depending on sowing date, plants can produce from 12 to >40 leaves on the main culm, with height varying from 1 m to more than 5 m. The present study aimed to better understand the complex phenology of these variables.

Methods

A 2-year series of monthly sowings of three West African sorghum varieties was conducted near Bamako, Mali. Drought stress was avoided by supplemental irrigation. Rate of initiation of primordia at the stem apex was recorded, together with rate of leaf emergence and increase in plant height.

Key Results

Leaf initiation and appearance rates (plastochron−1 and phyllochron−1) were constant for a given sowing date in cases where less than 20 leaves were produced (generally observed with late sowing dates). In contrast, rates were bilinear for early sowing dates, for which plants produced more than 20 leaves. The secondary rates, which occurred from the 20th leaf onwards, were only half of the initial rate. Plastochron and phyllochron showed large variations among sowing dates, and were correlated with the rate of plant height increase. The initial plastochron and phyllochron were positively correlated with soil temperature and negatively correlated with both day length and day-to-day change of day length prevailing at plant emergence, but these factors explained only half of the variation observed.

Conclusions

Although they belong to different genetic groups and have different height and photoperiod sensitivity, the three varieties studied exhibited similar response patterns of development rates among phenological phases and seasons, with the local landrace showing the greatest variation due to its longer vegetative phase and longer stem internodes. The possible adaptive advantages in African savannah environments of bilinear development rates and the associated limitation in height increase are discussed.

Keywords: Sorghum bicolor; phenology; plastochron; phyllochron; photoperiod; stem growth

Journal Article.  9976 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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