Abstract

The objective of this study was to assess the influence of planting density, growth environment and the seasons over the conversion efficiency (εb) of intercepted photosynthetically active radiation into biomass of Eucalyptus dunnii Maiden seedlings. An experiment was carried out using two plantings densities (100 % and 50 % occupancy), two growth environments (natural environment and greenhouse environment) during two growth seasons (summer and fall). Determinations of net primary biomass production, leaf area index and interception of the photosynthetically active radiation were taken, which allowed the calculation of εb. Null hypothesis was rejected - the factors investigated (plant density, growth environment and seasons) influenced the values of εb. The higher observed εb was 7.59 g MJ‑1, obtained in the experiment conducted during summer, under greenhouse conditions and at 100 % tray density. Factors did not depend on εb, pointing that the greater εb was observed in the greenhouse environment and with a planting density of 100 %, independently of the season. Therefore, the factors assessed had influence over net primary biomass production of Eucalyptus dunnii Maiden seedlings, resulting in a longer or shorter residence time of the seedlings in the nursery.

Highlights

  • Forest stands of Eucalyptus genus occupy an area of 5.7 million hectares of area trees planted in Brazil (IBÁ, 2017)

  • The accumulation in total dry mass of Eucalyptus dunnii seedlings was evaluated in the seasons: summer and autumn; in cultivation environments: natural and protected; and in two levels of plant densities in the trays: 100% and 50%, called high and medium density, respectively

  • The second cycle occurred in autumn, in which the global solar radiation flow averaged 12.5 MJ m-2 day-1, with a range from 1 to 27.6 MJ m-2dia-1, already inside the greenhouse, averaged 7 MJ m-2 day-1, with a variation from 0.6 to 15.5 MJ m2 day-1 (Figure 1)

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Summary

Introduction

Forest stands of Eucalyptus genus occupy an area of 5.7 million hectares of area trees planted in Brazil (IBÁ, 2017). Greenhouse cultivation causes changes in meteorological elements such as, for example, solar radiation (CARON et al, 2012) This element directly affects the growth and development of seedlings, since it is a function of the phytomass balance accumulated by photosynthesis (CARON et al, 2012). Variables that alter photosynthetic processes are of interest to professionals linked to the areas of agrarian sciences, because the plant productivity and crop yields depend on photosynthetic rates (TAIZ and ZEIGER, 2004). In this sense, the phytomass production of a plant depends on the amount of photosynthetically

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