Abstract
ABSTRACT The effects of root deformation caused by errors in the pricking-out process in forest nurseries are still unknown for tropical tree seedlings. We analyzed the effects of light availability and root deformation on growth and biomass allocation in seedlings of Senna multijuga, a pioneer tropical tree commonly used in forest restoration programs. Our hypotheses were: (a) as a typical light-demanding species, the seedlings of S. multijuga may have their growth compromised by low light availability; (b) root deformation impairs growth rates and induces changes in biomass allocation; and (c) the effects of low light availability on growth and biomass allocation are increased by root deformation. Seedlings with and without root deformation were cultivated for 43 days under three levels of total daily photosynthetically active radiation (PAR) (28, 12, and 1 mol photons m-2 day-1). Seedlings of S. multijuga had their growth rates severely affected by values of PAR at about 1 mol photons m-2 day-1, but root deformation did not affect the relative growth rates of the whole plant. Instead, root deformation caused a decrease in the relative growth rate of roots in all light availabilities. The changes in root growth affected biomass allocation to the roots. The interactive effects of light availability and root deformation on the allocation of biomass to leaves are more pronounced at low light availability. Root deformations may lead to the production of seedlings with a low competitiveness capacity regardless of light conditions.
Highlights
Forest degradation in the tropics has caused the loss of habitats for flora and fauna and has been promoted through anthropic activities, such as logging, hunting, and deforestation for agricultural expansion (Calegari et al, 2010; Giam, 2017)
Our hypotheses were as follows: (a) as a typical light-demanding species, the seedlings of S. multijuga may have their growth compromised by low light availability; (b) root deformation impairs growth rates and induces changes in biomass allocation; and (c) the effects of low light availability on growth and biomass allocation are increased by root deformation
From a practical point of view, our results show that root deformation caused by errors during the pricking-out process potentially makes tree seedlings more susceptible to adverse factors in the field, which can lead to reduced survival rates and growth of these seedlings
Summary
Forest degradation in the tropics has caused the loss of habitats for flora and fauna and has been promoted through anthropic activities, such as logging, hunting, and deforestation for agricultural expansion (Calegari et al, 2010; Giam, 2017). Due to the initial fragility of tree seedlings, the seedling production process requires appropriate management strategies in the nursery to obtain a better uniformity of height and a well-formed root system because these qualities can promote satisfactory survival and growth in the field, even under adverse conditions (Gomes et al, 2002; Thomas et al, 2008). Plants depend on their roots for soil anchorage and the absorption of water and nutrients (Lynch, 1995; Amoroso et al, 2010). Several nursery manuals draw attention to problems arising from root deformation at the time of pricking out (Carneiro, 1995; Jaenicke, 1999; Gregorio et al, 2010; Wilkinson et al, 2014), the topic has never been the focus of intensive experimental studies or the subject of experiments on the interactive effects of root deformation and environmental stress
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