The overall aim of this thesis was to investigate the interactive effect of temperature and photon flux density (PFD) on vegetative and reproductive growth responses of Shiraz vines in vineyard conditions. It was hypothesised that the effect of high summer temperatures on the growth and development processes of vines is exacerbated by exposure to high PFDs. To evaluate this hypothesis, vines were covered with 0%, 10%, 30% and 50% shade cover in vineyard conditions over three consecutive growing seasons. The vines were managed through irrigation so that they did not experience any water constraints. Several high temperature heat events, i.e., air temperatures exceeding 40oC for several days, occurred in 2013/14. Additionally, to assess the hypothesis, a controlled environment experiment was conducted at 25/12Ã‚°C and 32/20Ã‚°C and 350 µmol m-2 s-1 and 700 µmol m-2 s-1 to determine dynamics of vegetative growth.Shade treatments reduced canopy temperatures by 3.2 - 6Ã‚°C in the cooler season (2011/12) and by 4 - 6Ã‚°C in the warmer season (2013/14) relative to air temperature. Furthermore, diurnal canopy temperatures of shaded vines were reduced by 5 - 7Ã‚°C and bunch temperatures by 2 - 13Ã‚°C compared with the open canopy treatment. There were no indications of primary bud necrosis in the study which is related to the shade. Relative growth rates in the medium to heavy shade treatments were increased in comparison with control and light shade treatments but shade had no effect on final shoot lengths. The expansion rate of early emerging leaves was reduced in comparison to late emerging leaves and internode lengths were longer in the medium and heavy shade compared to control and light shade treatments. Dry matter allocation to leaves and internodes was also affected, with a shift in allocation from the leaves to the internodes as the shade intensity increased. There were no significant treatments effect on flowering and fruit set whereas there was a seasonal effect on fruit set. Veraison was delayed 8 days in the heavy shade treatment relative to light and control treatments in the 2011/12 and 2012/13 seasons, respectively. Berry soluble solids accumulation was delayed by the heavy shade treatment but sugar accumulation was not affected. Rates of sugar accumulation were reduced markedly by the 2013/14 heat event in the light shade treatments whereas rates of sugar accumulation were not penalised in the medium and heavy shade by the heat event. However, there were marked effects of season on sugar accumulation, much less sugar accumulated in berries during the warm 2013/14 compared to the cool 2011/12 season. Heavy shade also delayed the timing of berry expansion and dry matter accumulation in berries. During the season with the heat event, berry dry matter accumulation was markedly higher in the shaded treatments compared to the unprotected control vines. Nevertheless, there was no marked effect of shade on yield of Shiraz vines.Temperature and photon flux density interacted to affect growth of the Shiraz vines in the controlled environment conditions, higher shoot lengths but slower dynamics occurred in low compared to high temperature and high PFD. There were also interactive effects on leaf expansion and internode extension with time of leaf emergence also impacting on the response. The sizes of early emerging leaves and internodes were not altered but the dynamics and sizes of mid and late emerging leaves and internodes were affected by both temperature and PFD.It was concluded that the vegetative and reproductive growth of Shiraz vines were negatively impacted on by high summer temperatures and their concurrent exposure to high PFDs was also detrimental to their growth.
|Qualification||Doctor of Philosophy|
|Award date||01 Jun 2016|
|Place of Publication||Australia|
|Publication status||Published - 2016|