Factors involved in alleviating water stress by partial crop removal in pear trees (original) (raw)
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Sensitivity of root pruned ‘Conference’ pear to water deficit in a temperate climate
Agricultural Water Management, 2011
The present study examines the need for irrigation in pear trees (Pyrus Communis, cv. 'Conference') under low evaporative demand conditions, like in Belgium, in order to maintain a consistent fruit yield and high fruit size. To determine the sensitivity of the pear yield under low evaporative demand conditions three different orchards were monitored. The study shows that a « soil of −60 kPa during shoot growth has no effect on fruit yield but lower « soil values induced a decline in both fruit size and total yield. Just as for arid environments a « stem of −1.5 MPa is related to negative yield responses. In dry conditions lower « soil and « stem values were observed in root pruned trees compared to not root pruned trees in the same irrigation treatment, however without yield decline. In one orchard a biannual bearing tendency was observed after root pruning. Furthermore intensive « soil measurements show a high variation in « soil between orchards, and within an orchard. This underlines the need for irrigation management on a parcel level and the need for new irrigation scheduling techniques which take the spatial variation in the orchard into account.
Plant Water Status as an Index of Irrigation Need in Deciduous Fruit Trees
HortTechnology, 1997
To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential...
2005
The hypothesis that different fruit loads between 'scaffold branches' of a tree can induce water status differences was evaluated. Two different experiments were carried out, one under full irrigation conditions and the other under conditions in which peach trees were deficit irrigated (50%). Thinning treatments were applied in both experiments at the begining of Stage III of fruit development: 1) EVEN-max with fruits distributed evenly with maximum crop, not thinned, 2) EVEN-min with fruits distributed evenly with minimal crop (< 90 fruit tree -1 ), and 3) UNEVEN with fruits distributed unevenly by totally defruiting half of the available main (scaffold) branches per tree and leaving the other half unthinned. Stem water potential (⌿ stem ) was measured with a pressure chamber at solar noon, and midday leaf conductance (g l ) using a portable steady state porometer. UNEVEN trees always had intermediate ⌿ stem values between EVEN-max and EVEN-min, independent of irrigation treatments. Maximum fruit load differences between trees (EVEN-max compared to EVEN-min) produced ⌿ stem differences of 0.12 MPa and 0.25 MPa for full irrigation and deficit irrigation experiments, respectively. Although the magnitude of change in ⌿ stem was larger for deficit irrigated conditions, extreme differences in fruit load between main branches within an UNEVEN peach tree only induced differences in leaf conductance and had no effect on the water potential of scaffold branches independent of the irrigation experiment. Fruit load effects on branch water status were governed mainly by tree fruit load rather than scaffold branch fruit load. These results indicate that there is either little hydraulic isolation between the main stems, irrespective of tree water status, or an improved hydraulic efficiency associated with defruiting.
The Effect of Reduced Soil Water Status on 'Golden Delicious' Apple Trees
X International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems, 2014
In the Western Cape, South Africa, uncertainty exists regarding effects of global warming-induced climatological changes on limited water resources, as well as the future incidence and extent of droughts. A need to employ appropriate irrigation strategies timeously during drought periods, instigated research concerning the possibility to maintain optimum fruit yield and quality by means of deficit irrigation (DI) in the Koue Bokkeveld production region. 'Golden Delicious' apple trees on M793 rootstock were subjected to 15 treatments, which consisted of irrigation at combinations of 50%, 75% or 90% plant available water (PAW) depletion or no irrigation during four phenological phases viz. vegetative growth and cell division (Phase 1), cell enlargement (Phase 2), fruit ripening (Phase 3) and post-harvest (Phase 4). The vegetative growth, yield and fruit quality response of the trees to these treatments were evaluated during 2005/06, 2006/07 and 2007/08. Plant physiological data were collated in 2005/06 at the end of Phases 1, 2 and 3. In 2005/06, leaf (Ψ l) and stem (Ψ s) water potential correlated well at predawn and midday. Cloudy conditions interfered with midday photosynthesis measurements of Phase 2. Water deficits during Phases 2 and 3 decreased predawn Ψ s at the end thereof from ca.-0.43 MPa to ca.-1.67 MPa and ca.-1.41 MPa, respectively. At the end of Phases 1, 2 and 3, midday Ψ s decreased from ca.-1.1 MPa to ca.-1.8 MPa,-2.4 MPa and-2.2 MPa, respectively. At the end of Phase 1, leaf photosynthesis, stomatal conductance and transpiration tended to decrease with decreased midday Ψ s. During Phase 3, increased leaf temperatures tended to exacerbate water deficit effects on photosynthesis. Under the prevailing conditions, DI during Phases 1 and 3, respectively, may be partially accountable for decreased shoot and/or fruit growth rates, and eventually lower yield and fruit quality.
2020
The INTRODUCTION In fruit trees, the environmental interactions during the annual growth stage may determine significant alterations in the relationship between the scion and the rootstock, occasioning associated eco-physiologic changes related directly with the final yield production. In general, abiotic stress conditions, such as lack of water, may induce different biomass production and partitioning within the tree, with an increase in accumulated dry matter in roots, possibly damaging canopy volume (Landsberg and Jones, 1981). Root-shoot relations appear to be governed by a functional balance between water uptake by the root and photosynthesis by the shoot. However, this functional balance is shifted if the water supply decreases. The main effect of water stress on vegetative growth is the inhibition of leaf expansion and consequently the decrease of photosynthetic activity (Taiz and Zeiger, 2004). Massai and Gucci (1997), studying transpiration and water balance in peach trees ...
Tree Physiology, 2020
Adaptations of fruit trees to future climate are a current research priority due to the rapid increase in air temperature and changes in precipitation patterns. This is aimed at securing sustainable food production for our growing populations. Key physiological traits in trees conferring drought tolerance are resistance to embolism and stomatal control over water loss. Recently, we have shown in the field that a native wild pear species performs better under drought than two cultivated pear species. A comparative greenhouse study was conducted to investigate traits associated with drought tolerance in four ecotypes of a wild pear species (Pyrus syriaca Boiss), compared with a wild pear species (Pyrus betulifolia Bunge) commonly used as a pear rootstock. Seed sources were collected from semi-arid, sub-humid and humid sites across northern Israel. Measurements of water relations, leaf physiology, hydraulic conductivity and percent loss of hydraulic conductivity (PLC) were conducted un...
Plant and Soil, 2012
Aims Climate, soil water potential (SWP), leaf relative water content (RWC), stomatal conductance (g s), fruit and shoot growth, and carbohydrate levels were monitored during the 2008 and 2009 growing seasons to study the responses of 'Gala' and 'Fuji' apple trees to irrigation placement or volume. Methods Three irrigation treatments were imposed, conventional irrigation (CI), partial root-zone drying (PRD, 50% of CI water on one side of the root-zone, which was alternated periodically), and continuous deficit irrigation (DI, 50% of CI water on both sides of the root-zone). Results After each irrigation season, DI generated twice the soil water deficit (SWD int) than PRD (average of dry and wet sides) and a greater integrated leaf water deficit (LWD int) than PRD and CI. Both PRD and DI reduced g s by 9 and 15% over the irrigation period. RWC of both PRD and DI was directly related to SWP and inversely related (non-linear) to vapor pressure deficit (VPD), whereas it was unrelated to g s. Considering individual sampling days, g s of 'Gala' leaves was inversely related to VPD mainly until early August (fruit at cell expansion phase and high VPD), while it was directly related to VPD in September (no fruit and low VPD). On the contrary, g s of 'Fuji' leaves was inversely related to VPD from late August until mid October (low VPD and fruit at cell expansion phase). Fruit growth was not affected by irrigation, whereas shoot and trunk growth was reduced by DI. Irrigation induced sporadic and inconsistent changes in carbohydrate contents or partitioning, with a general tendency of DI leaves to degrade and PRD to accumulate sorbitol and sucrose in dry periods. Conclusions 'Gala' trees exhibited a more conservative water use than 'Fuji' trees due primarily to different timing of fruit growth and crop loads. Different levels of SWD int , rather than changes in stomatal control and carbohydrate partitioning, seem to play a major role in determining a better water status in PRD than in DI trees.
Fruits, 2005
Abstract --Introduction. Vegetative and fruit growth in fruit trees are differentially sensitive to water deficit during the season depending on the stage of fruit growth. Attempts have been made to evaluate the possibilities of using regulated deficit irrigation to control vegetative growth and save water in the fruit industry. Materials and methods. Effects of water stress (WS) and crop load (CL) on fruit growth and carbon assimilation rates were evaluated in a 7-year-old 'Elegant Lady' peach orchard. A completely randomized block design with 2 × 3 factors [irrigation with two levels (control and WS) and CL with three levels (light, commercial and heavy)] was used. Results and discussion. Both WS and CL affected fruit growth during the last stages but not early on. CL did not affect trunk water potential which was, however, significantly reduced by WS throughout the day and the season. Trunk water potential of water-stressed trees was lower than that of control trees throughout the day and the season regardless of CL. The magnitude of WS increased as the season progressed. Stomatal conductance, transpiration rate and CO 2 assimilation rate were not affected by CL but were reduced by WS. The trees responded (acclimated) to stress by progressively reducing their transpiration rate as the severity of stress increased. For each irrigation regime, assimilation rates were similar for all three crop levels. This indicated the existence of alternate sinks for assimilates when CL was low, which compensate for the reduction of fruit sink activity resulting from fruit thinning. Conclusion. Water deficit reduced trunk water potential, stomatal conductance, transpiration and photosynthesis in 'Elegant Lady' peach trees. However, CL had a limited effect on these functions. There were good correlations between trunk water potential and either stomatal conductance or assimilation rate in water-stressed trees but not in control trees. This indicates a poor coordination between leaf functions in peach trees under optimal conditions. However, these relationships were stronger under WS conditions. Thus, water use efficiency appeared to increase under water deficit conditions.
Annals of Forest Science, 2006
The extreme drought event that occurred in Western Europe during 2003 highlighted the need to understand the key processes that may allow trees and stands to overcome such severe water shortages. We therefore reviewed the current knowledge available about such processes. First, impact of drought on exchanges at soil-root and canopy-atmosphere interfaces are presented and illustrated with examples from water and CO 2 flux measurements. The decline in transpiration and water uptake and in net carbon assimilation due to stomatal closure has been quantified and modelled. The resulting models were used to compute water balance at stand level basing on the 2003 climate in nine European forest sites from the CARBOEUROPE network. Estimates of soil water deficit were produced and provided a quantitative index of soil water shortage and therefore of the intensity of drought stress experienced by trees during summer 2003. In a second section, we review the irreversible damage that could be imposed on water transfer within trees and particularly within xylem. A special attention was paid to the inter-specific variability of these properties among a wide range of tree species. The inter-specific diversity of hydraulic and stomatal responses to soil water deficit is also discussed as it might reflect a large diversity in traits potentially related to drought tolerance. Finally, tree decline and mortality due to recurrent or extreme drought events are discussed on the basis of a literature review and recent decline studies. The potential involvement of hydraulic dysfunctions or of deficits in carbon storage as causes for the observed long term (several years) decline of tree growth and development and for the onset of tree dieback is discussed. As an example, the starch content in stem tissues recorded at the end of the 2003's summer was used to predict crown conditions of oak trees during the following spring: low starch contents were correlated with large twig and branch decline in the crown of trees.
Journal of Plant Growth Regulation, 2012
Responses to deficit irrigation (DI) throughout the fruit-growing season were studied in 'Conference' pear grafted onto quince M-A rootstock and grown in large containers. The treatments were (1) full irrigation (FI), (2) DI during Stage I of fruit growth (DI-Stage I), and (3) DI during Stage II of fruit growth (DI-Stage II). Four whole trees were sampled before Stage I and from all treatments at the end of Stage I, end of Stage II (fruit harvest), and before leaf fall. There was less discrimination against 13 CO 2 in DI leaves, indicative of reduced photosynthetic capacity. DI treated trees had lower starch content in branches and trunks but root starch concentration was the same between DI-and FI-treated trees. Compared to FItreated trees, leaf, shoot, branch, and trunk dry biomass was reduced by 34, 50, 37, and 32 %, respectively, in DI-Stage I and by 45, 73, 37, and 22 % in DI-Stage II. Root growth was not affected by DI. Trees had limited capacity for storing starch in roots. Recovery of the aboveground starch concentration for DI treatments occurred within 1 month after rewatering but total starch content never recovered.