Abstract
Improving crop productivity through higher plant density requires a detailed understanding of organ development in response to increased interplant competition. The objective of this paper is thus to investigate the characteristics of organ development under increased interplant competition. A field experiment was conducted to investigate organ development across 4 maize plant densities i.e. 2, 6, 12 and 20 plants m–2 (referred to PD2, PD6, PD12 and PD20 respectively). In response to increased interplant competition, lengths of both laminae and sheaths increased in lower phytomers, but decreased in upper phytomers. Sheath extension appeared to be less sensitive to increased interplant competition than lamina extension. Extension of laminae and internodes responded to increased plant density as soon as onset of mild interplant competition, but did not respond any further to severe competition. Both lamina width and internode diameter were reduced due to a smaller growth rate in response to increased plant density. Overall, this study identified that organ expansion rate can be taken as the key morphological factor to determine the degree of interplant competition.
Highlights
Optimising high plant density may increase the potential for achieving greater crop yield since there are more plants available per single harvesting unit
The results indicated that lamina extension in lower and middle phytomers quickly responded to mild and moderate interplant competition, but arrested to respond further to more severe competition
Lamina length was significantly reduced by 6.6, 11.1 and 16.2% for phytomers 16–18 respectively when plant density increased from PD2 to PD6 (Fig 1a); by 9.1, 12.7, 14.8 and 21.5% for phytomers 15–18 respectively when plant density continued to increase from PD6 to PD12 (Fig 1a); and by 3.5, 4.8, 8.2, 10.1, 12.8, 13.4 and 17.6% for phytomers 12–18 respectively when plant density further increased from PD12 to PD20 (Fig 1a)
Summary
Optimising high plant density may increase the potential for achieving greater crop yield since there are more plants available per single harvesting unit (e.g. per hectare). Crop growth and yield in maize depends on incident radiation intercepted by the canopy [8,9] and light composition of intercepted radiation such as Red (R): Far Red (FR) [10,11]. Both intercepted light quantity and its quality in the canopy are largely determined by canopy.
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