Trunk measurement events in ET treatments

Stem diameter measurements for each treatment during 4-day periods are plotted in Figure 6 for trees ETF, ETRC and ETLC. In the 100% ET treatment between April 27 and April 30, MXD increased during the last three days for all the trees and water was always available at the soil, Figure 6A. Arrows in the figure show irrigation scheduling.

At sunrise, air temperature decreased to minimum values beneath 21°C, but during April 28^th, night temperature remained in 23 causing MXD to drop in all trees. The morning slope MS of canopy-only trees was similar, but different from the ETF that presented inflorescences and seven fruits in growing stage. ETF morning slopes were of - 515±10.2%, being the steeper on April 28^th. ETF black line signal on the afternoon of April 27 shows a linear AS of 319.15 from 16:40 up to 20:00. ETF encounters its MND at the V inverted peak and matches with the maximum air temperature peak.

The ETRC trunk diameter shrinked to -46.7 µm (29^th of April), taking the soil water available directly for plant evapotranspiration without any trunk water storage; This period lasted seven hours. The ETRC (pointed line) presented the lower MXD, but on days 28, 29 and 30 of April, its magnitude was close to the one of ETLC that had a greater canopy. As noon temperature decreased daily, plant evapotranspiration and MND declined also (VPD=2.32). On both 28 and 29 of April, night slope was present in all the trees, resulting in tree growth.

As soil water available remains for 3 or four days after water shortage, stress was monitored in trees from May 20 to May 23, corresponding to the second stress week. In this period, MXD values ranged between 23.7 and 35.76 µm for ETF, Figure 6B. On 20^th and 23^th of May, warmer nights dropped MXD to 23.84 µm. ETF morning slopes differed for the four days (- 476±22%), having the 20^th and 21^th day of May two different slopes between 7:00 and 10:00, with a peak between them; the average of the growing fruits 94.4±10% grams. At noon, ETF trunk diameter measured zero microns for the first three days. ETF maximum shrinkage MND (-25.72 µm) during May 21 and May 22,

78 occurred at 15:50 and 15:00, respectively. From this point onwards, water moving through the trunk got stored as plant evapotranspiration decreased (2.23 to 2.64).

Figure 6 Trunk variations of ETLC —, ETRC --- and ETF

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The tree with lower canopy (ETRC-pointed line) also presented the lower MXD in this stress period. On May 20^th, with the dew temperature at 24.19°C, ETRC trunk diameter dropped to a (MXD) maximum value of 11.8 µm. Scarce soil water availability combined with high night air temperature of 24.75°C at 7:40 on May 23, limited trunk growth to 11.92 µm (Figure 6B). The afternoon slope differed all days and was only present until 17:40. The low soil water available was used during a 7-hour period to provide controlled plant evapotranspiration. By the 23^th May, leaves started wilting and their inclination decreased.

Both trees having only vegetative cover (ETRC & ETLC) presented similar morning slopes; ETLC=-767±12.2%, and ETRC=-749±14.2%. However, the ETLC tree presented several peaks just after the morning slope. As the tree (ETLC-slim continuous line) has 810 leaves, trunk dimensions and branches vary due to their water distribution and storage throughout the 9:00 to 18:00 periods. This tree with the pivotal continuous stem provides

79 higher MXD and lower MND; higher leaves in this branch suffered premature wilting compared to lateral branches fixed to the tutors. As air temperature increases for periods, stomatal conductance rises and trunk shrinks more. The difference in leaf cover is clearly noted during this stress period. The ETLC stressed tree showed on June 20^th poor trunk shrinkage (oscillating between -8 and -14 µm) with the scarce soil water available.

Just after a period of 210 mm of rainfall up to June 5^th the trial zone experienced, nights remained warm, and MXD decreased to 17.9 µm in the ETRC tree, from June 17 to June 19. The night temperature of July 18 was 26.53°C and the MXD of the fruit bearing tree (ETF) was of 41.7 µm. The next two days, dew temperature decreased to 24.3°C and MXD reached maximum values of 53.6 and 59.6 µm. The two morning slopes in the ETF stem are temperature dependent; in the first MS slope (-448±28%), temperature rises quicker (3.4°C hr^-1), meanwhile in the second MS temperature rises to a peak with a reduced gradient (0.6°C hr^-1). The maximum peak of 29.8 µm between the two MS indicates trunk water storage to provide water requirements to the growing fruits with an average of 104±8 grams. Stem diameter variations should be considered within the water balance and the sugar content of mango trees (Daudet et al., 2005); In mango trees the sugar content of woody tissues changes as a function of fruits. Trunk diameter plots find the MND value, according to the phenological stage tree considered. For example, the ETF tree always have the MND in the bottom point of the V graph being of -39.7 µm at 14:50. ETRC MXD varied between 18 and 41 µm, in the period from June 17 to June 20.

The ETLC tree was the one that grew more, having two different slopes in the afternoon.

During this period MXD varied from 50.7 to 74.5 µm in the ETLC tree.

Table 2 correlations found with the signals of figures 6 and 7. MXD and MND considerations of trees under ET and stress treatment.

MXD Considerations MND Considerations

ETF Two morning different slopes

Mostly before noon

ET ETRC MDX is temporized with Tmin MND is temporized with Tmax

ETLC Trees are out of phase in stress and rain

ETF Presents more NS than others. MND at 14:10

STRESS ETRC Trees wilted after 7 day ETRC to -10 in stress ETLC Increasing Tdew, MXD rises

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