Photosynthetic capacity and diurnal gas exchange of ‘Brookfield Gala’ apple leaves under three irrigation systems

Abstract

ovember 2010Water and nutrient application using three irrigation systems, namely daily drip irrigation, pulsing drip irrigation and micro irrigation were studied with respect to photosynthetic efficiency, water use efficiency and leaf water relations in 'Brookfield Gala' apple trees during 2004/5 and 2005/6 for the pulsing drip for 2004/5 and 2005/6 seasons respectively. Trees were budded on either M793 or M7 rootstocks and planted in blocks using a split-plot experimental design with irrigation as the main effect and rootstock as the sub-plot. Maximum light-saturated net CO 2 assimilation rate (A max ) was consistently higher under pulsing drip irrigation (this system applies water several times during the day creating an even shorter frequency cycle than the normal daily drip) compared to micro irrigation (applies water once to twice a week and uses sprinklers that spray water in a circle resulting in wetting a continuous strip within the drip row) but, occasionally, significantly higher than daily drip irrigation (applies water on a daily basis creating a shorter cycle compared to micro sprinkler system). The maximum rate of electron transport (J max ) showed similar trends to A max during 2004/5, but not during 2005/6. A max peaked during midmorning (10h00) with a steady decline thereafter in all treatments, but with significantly lower rates under micro irrigation. Stomatal conductance (g s ) declined steadily throughout the morning, with higher g s under the drip based systems compared to the micro system. The implications are that, irrigation application should be given early in the morning to sustain stomatal conductance and maximise CO 2 assimilation rates during the period between 08h00 to 12h00. Results indicate higher photosynthetic capacity and water use efficiency under both drip-based irrigation systems compared to micro irrigation. Differences in photosynthetic capacity were related to both stomatal and non-stomatal responses.

Grey and Black Anti-Hail Nets Ameliorated Apple (Malus × domestica Borkh. cv. Golden Delicious) Physiology under Mediterranean Climate

“…Interestingly, the likely attenuation of stressful conditions under the netting systems also alleviated the midday depression of photosynthesis, due to both lower stomatal and non-stomatal limitations. (Figure 1) Such responses of fruit trees under shading conditions are supported by the literature [42,44,46], as light, temperature and VPD are usually more determinant for midday depression of photosynthesis than tree water status and soil water availability [49,51].…”

“…The midday depression of photosynthesis is a common phenomenon in C3 plants, including apple trees, due to the stomatal closure and/or photoinhibition caused by the accentuation of stressful conditions [42,[48][49][50]. Interestingly, the likely attenuation of stressful conditions under the netting systems also alleviated the midday depression of photosynthesis, due to both lower stomatal and non-stomatal limitations.…”

High Levels of Shading as A Sustainable Application for Mitigating Drought, in Modern Apple Production

“…During the seasons of 2013 and 2015, irrigation treatments seemed to play a major role in determining final fruit size, with lower marketable yields in ws trees (Table 6). This may be partly explained by the reduction in leaf gas exchange activity (A n and g s ) ((Tables 2 and 3) due to the more negative mSWP experienced by ws trees (Figure 2) [36]. As AGR was linearly related to mSWP (Table 7), it appears evident that low amounts of water will decrease seasonal fruit growth, and therefore marketable yield will be penalized [37,38].…”