Contributions of early season temperatures to pyrus communis 'Bartlett' fruit growth

Abstract

Final size of pear fruit depends on genetics, environmental and different management factors. The aim of the present study was to examine how natural temperature fluctuations affected growth of ‘Bartlett’ cultivar fruit. The fruit growth of ‘Bartlett’ pear was studied under field conditions during 2006 and 2007. Each year, ten small fruit and ten large fruit were randomly sampled and weighted from 10 different trees. Sampling began 10 days after full bloom (DAFB) until 60 DAFB with a frequency of 10 days. Total cell number and mean cell size were determined in mesocarp tissue. Mean temperatures were recorded hourly during each season. As a result of our observations, growth of ‘Bartlett’ pear fruit can be described by an initial exponential phase that extends for 30 days of cell division, followed by an inter-phase of cell division and cell expansion and finally a lineal phase where growth is due to cell expansion. Temperature has a major influence on fruit growth rate during the cell division phase. There was a highly significant correlation during the cell division phase between fruit growth rate (g day-1) and daily mean temperature (from 11 to16.5°C), for large fruit (R2=0.96) and small fruit (R2=0.77). Seasonal variation in final size of ‘Bartlett’ pear could be determined by temperature effect during cell division and resource allocation before full bloom.