Physiological and yield responses of rainfed grapevine under different supplemental irrigation regimes in Fars province, Iran

Scientia Horticulturae 202 (2016) 133–141

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Physiological and yield responses of rainfed grapevine under different supplemental irrigation regimes in Fars province, Iran Masoomeh Mazaheri Tehrani a , Ali Akbar Kamgar-Haghighi a , Fatemeh Razzaghi a,∗ , Ali Reza Sepaskhah a , Shahrokh Zand-Parsa a , Saeid Eshghi b a b

Water Engineering Department, Agricultural College, Shiraz University, Iran Horticultural Science Department, Agricultural College, Shiraz University, Iran

a r t i c l e

i n f o

Article history: Received 23 October 2015 Received in revised form 20 February 2016 Accepted 25 February 2016 Keyword: Table grape Effective rainfall Photosynthesis rate Stomatal conductance Leaf water potential

a b s t r a c t Supplemental irrigation, which provide minimum amount of water under rainfed farming systems, improves the physiological characteristics and yield production of plants especially in arid and semiarid regions. However, the amount and timing of supplemental irrigation are of utmost importance and challenging with the recent drought occurrences. A two-year field experiment was carried out to study the effect of different supplemental irrigation timings (March, April, May, June, March + April and no irrigation, denoted I1 , I2 , I3 , I4 , I5 and I6 , respectively) on stomatal conductance (gs ), photosynthesis rate (An ) and leaf water potential of rainfed seedless Table grape, cv. Yaghooti. The I1 , I2 , I3 and I4 treatments received 500 l of water, while I5 treatments received 1000 l of water during the growth season, respectively. The significant maximum berry weight was obtained in the I3 treatment in both years indicating the efficient use of applied water. Maximum and minimum values of An and gs were 12.10 ␮mol m−2 s−1 and 0.133 mol m−2 s−1 in I4 (in 114 days after first irrigation initiation), and 6.54 ␮mol m−2 s−1 for I5 and 0.068 mol m−2 s−1 for I1 , respectively. It is concluded that supplemental irrigation during May (I3 ) yielded more grape production, although it received less water compared to I5 treatments. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Rainfed agriculture covers 80% of the world’s agricultural area and contributes at least two-thirds of the world’s food production (FAO, 2005). However, agricultural production in rainfed regions of arid and semi-arid countries are low due to low rain water use efficiency as a result of inappropriate soil water and nutrient management strategies (Oweis and Hachum, 2006). Besides, soils in semi-arid and arid regions are often shallow, with gravel and poor in organic matter. These soils have low water holding capacity and low soil fertility (Van Leeuwen and Seguin, 2006). Increasing water scarcity, extreme temperatures, frequent drought, land degradation and desertification are the main challenges in rainfed areas (Oweis and Hachum, 2006). Drought, the most important abiotic stress especially in rainfed farming (Wu et al., 2007), occurs when soil available water is limited (Kramer, 1980). Reduction in soil water content diminishes soil and leaf water potential (Leuning et al., 2004), causes stomatal closure (Pellegrino et al., 2005),

∗ Corresponding author. E-mail addresses: [email protected], [email protected] (F. Razzaghi). http://dx.doi.org/10.1016/j.scienta.2016.02.036 0304-4238/© 2016 Elsevier B.V. All rights reserved.

decreases photosynthesis rate and eventually negatively affects ˇ crop growth and production (Chaves et al., 2003; Sircelj et al., 2007). Plants use three different mechanisms to compensate the negative effect of drought through drought-escape, drought-avoidance and drought-tolerance (Fageria, 1992). In rainfed agriculture, crops do not receive any additional water at any stage of their growth, apart from rain water (Gautam and Rao, 2007). While few horticultural crops (e.g. figs, almond, grape, olives) can grow in rainfed conditions, this type of farming (rainfed farming) can play a crucial role for agricultural production (Fooladmand and Sepaskhah, 2006). Grapevine (Vitis vinifera L.) is the most widely cultivated crop in the world (more than 10 million ha) and can grow in different climates varying from temperate to tropical regions (Riaz et al., 2004). Although, low precipitation, high temperature and evaporation demand in rainfed areas are limiting factors for grape yield production (Chaves et al., 2007), most of the rainfed grapes are located in arid and semi-arid regions where the amount of rainfall (less than 500 mm) is not sufficient for the plants to grow and the symptoms of water stress occur during the cropping season (Gautam and Rao, 2007). Therefore, supplemental irrigation can be an appropriate way to maintain and enhance the rainfed grape yield and its sugar content by moderating the negative effects of

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severe water stress (Reynolds et al., 2009). Supplemental irrigation involves providing small amounts of water to rainfed crops during the times when rainfall fails to provide sufficient soil water for normal plant growth (Oweis et al., 1998). In addition, farmers are faced with inadequate water resources due to over use of groundwater resources in arid and semi-arid regions, therefore, small amount of supplement irrigation at the right time in the growing season may sustain and even enhance yield (de Souza et al., 2005; dos Santos et al., 2003). The Islamic Republic of Iran with 275,000 ha is the second (after Turkey with 530,000 ha) grape producer among the Near East countries (FAO, 2006). In Iran, Fars province with 20.1 percent of total grapevine cultivated area is the largest compared to other provinces. This province is located in the southern part of Iran, with mean annual rainfall of 330 mm, mean temperature of 17 ◦ C (Torabi-Haghighi and Keshtkaran, 2008), and with semi-arid to arid climate (Nafarzadegan et al., 2012), where drought is a common event (Hashemi et al., 2013). Due to drought occurrence and low precipitation, most of the land use has been changed to rainfed farming, where different types of cultivars of grapevine has been cultivated. Grapevine is capable of physiological drought avoidance mechanisms, such as an efficient stomatal control of transpiration and of xylem embolism (Lovisolo et al., 2002) and the ability to adjust osmotically (Rodrigues et al., 1993). However, due to significantly lower rainfall in recent years especially during winter and spring in Fars province, the need for supplemental irrigation is essential (Tavakoli et al., 2012). Yaghooti grapevine, grown in different regions especially in South of Iran (warm regions), is an early ripening and high income cultivar (Rajaei et al., 2013). It is used as seedless Table grape and for juice. It has become the favorite cultivar among growers because of its remunerative prices and higher profitability. Grapevine (especially this cultivar) needs relatively little exposure to chilling (Nir et al., 1986) and is, therefore, suitable for growing in warm climates which do not have adequate chill hours. Although, many investigations have been conducted on physiological and agronomical performance of grapevine under different conditions, to the best of our knowledge no studies focused on the amount and timing of supplemental irrigation effect on grapevine growth and production grown under rainfed conditions in semi-arid region. Therefore, the present study was conducted to investigate the effect of different supplemental irrigation timings with 0 (rainfed treatment) and 500 l of water on physiological response of Yaghooti grapevine (Vitis vinifera L.) in rainfed conditions in Fars province, Iran.

2. Materials and methods The research was conducted in Experimental Station at College of Agriculture, Shiraz University, with latitude of 29◦ 43 27 N and longitude of 52◦ 36 19 E and 1810 m above mean see level. Two years of experiment (during 2010–2011 and 2011–2012 cropping seasons) was performed in a vineyard, three years after rejuvenation of a 40-year old vineyard (restoration of grape production by pruning, which yields younger stems). The experiment was carried out on seedless Table grape cv. Yaghooti. The grapevines had mean height of 1 m and canopy cover of 35%. The vines were on their own roots, trained as a head system. The experimental design was completely randomized design with 6 treatments and 4 replications (each of replicates was contained one vine). This area has a semiarid climate with an average of 386 mm of rainfall, 50% relative humidity and maximum temperature of 34 ◦ C. The rainfed vineyard had an area of approximately 12 ha, where different cultivars of grapevine had been grown. Twenty four basins (one meter radius and with a height of 20–25 cm bound) were built in a gravelly loam soil with 5–6% slope in vineyard. Inter and intra

row spacing of 3 and 3 m was chosen, respectively, due to the fact that the vines were grown under rainfed condition for long time, which resulted in severe pruning (Ngo, 2002; Strik, 2011). 2.1. Irrigation Due to drought in the study region, supplemental irrigation was used to offset this problem. There was embankment surrounding grapevine trees (height 20–25 cm and radius 1m) and water was applied to this embankment. There were six supplemental irrigation treatments including: (1) supplemental irrigation during March when plant are still in dormancy (I1 ); (2) supplemental irrigation during April (I2 ); (3) supplemental irrigation during May (I3 ); (4) supplemental irrigation during June (I4 ); (5) supplemental irrigation during March + April (I5 ) and (6) no supplemental irrigation (I6 ). The amount of water applied for treatments I1 –I4 was constant and equal to 500 l, treatment I5 received 1000 l (in two parts each 500 l in March and April), and treatment I6 did not receive any water. The time of applied irrigation is shown in Table 1. In order to prevent the invasion of any irrigation treatments on nearby treatment and also to avoid the interference of the basins along and across the rows, the distance between the treated plants was 6.0 m by discarding every other rows and plants in each row imposing the treatments. Soil volumetric water content was measured by neutron probe close to each plant in the basin. 2.2. Evaporation from soil surface Microlysimeters were installed in the soil 80–90 cm away from the plants trunk and weighted once or twice a week to determine the amount of soil evaporation (E, mm). The height and internal diameter of the microlysimeter tubes were 30 and 9 cm, respectively. 2.3. Actual evapotranspiration Actual evapotranspiration was estimated from soil water balance using the following equation: ETa = I + P − DP ± S

(1)

where ETa is the actual crop evapotranspiration between two continuous soil water content measurements (mm), I is the amount of irrigation water (mm), P is the amount of rainfall (mm), Dp is the amount of deep percolation (mm) and S is the difference in the two consecutive soil water content measurements (mm). If the soil water content decreased compared to its previous value the sign of S was considered as positive, otherwise, it is negative. Deep percolation was considered to be zero due to the deep grapevine root depth (ca. 10 m; discussed by Smart et al. (2006)). The amount of rainfall was obtained from a nearby weather station of the Agricultural College. Twenty four aluminum tubes with length of 1 m were installed vertically in soil at a distance of 40 cm from each grapevine plant trunk, to facilitate determination of soil water content with a neutron probe (CPN 503 DR). Soil water content was measured every two weeks and before each supplemental irrigation event at different depths (0–30, 30–60, 60–90 cm). Plant transpiration (T, mm) was calculated based on the difference between actual crop evapotranspiration and evaporation. 2.4. Effective rainfall Effective rainfall is defined as a portion of the precipitation stored in the plant root zone during rainfall season to meet crop evapotranspiration demands (Tsai et al., 2005). The effective rainfall was estimated considering two assumption; first, the grapevine

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Table 1 Date of applying irrigation as a supplemental irrigation on rainfed vineyard during 2010–2011 and 2011–2012. TreatmentsA

I1

I2

I3

I4

I5

Date during 2010–2011 Date during 2011–2012

20-Mar-2011 26-Mar-2012

18-Apr-2011 17-Apr-2012

17-May-2011 16-May-2012

4-June-2011 19-June-2012

20-Mar + 18-Apr −2011 26-Mar + 17-Apr −2012

A

Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ) and during March + April (I5 ).

root is very deep and hence the percolation below the depth of 90 cm can still be used by crop and can be considered as a component of effective rainfall. The amount of runoff was also counted as zero based on the irrigation method. Therefore, the effective rainfall (Reff , mm) during tree’s dormancy was calculated using the following equation: R eff = R-E

(2)

where R is the amount of rainfall (mm) and E is the soil surface evaporation determined by using microlysimeters (mm). 2.5. Leaf growth rate and plant canopy temperature To determine leaf growth rate, leaf length was measured by ruler every two weeks by selecting two similar leaves (in size and shape) on each vine (four vines per treatments) in all treatments. Plant canopy temperature was measured with an infrared thermometer (KYORITSU, 5500 model). The measurement accuracy of this portable equipment is ±2 ◦ C and it could measure within the range of −40–500 ◦ C. To calibrate the infrared thermometer, several fresh leaves were picked from the fully watered vines and drown in a pot contained pure water. After equilibrium, the temperature of the the pure water in the pot was determined using a mercury thermometer. Simultaneously, the infrared thermometer was used to determine the leaf temperature, and if any difference between the two determined temperatures was observed, the equipment was adjusted by changing the emissivity factor (varied between 0.30 to 1.90 in 0.01 steps) until its temperature reached the same temperature as the mercury thermometer. The measurement was performed at a distance of 0.5 m and 45◦ -inclination angle to the leaf surface. In order to diminish the errors occurred by the direction towards the leaf, the canopy temperature was measured from four cardinal directions of each vines between 1 to 2 pm every two weeks. 2.6. Dry matter and yield At harvest time, all the clusters of each vine harvested and weighted directly. The leaves and newly annual produced shoots were cut and then dried in oven at 70 ◦ C for 72 h. The newly produced shoots were cut at two different time including 84 DAI (days after first irrigation on 20 Feb. 2011) and 102 DAI. 2.7. Physiological measurements Two youngest expanded leaves were selected and cut from the top of the canopy between 1 and 3 pm at 86, 98, 134, 141 and 186 DAI. The leaves were then wrapped in plastic bag and put in pressure chamber (Soil Moisture Equip. Corp. Mod. 5100A, Santa Barbara, CA, USA). The cut surface of the petiole was observed through a dissection microscope while the pressure was gradually increased until xylem water became visible and the balancing-pressure reading was taken. Leaf water potential (LWP) measurements were made before and after irrigation days. Leaf photosynthesis (An ), stomatal conductance (gs ) and transpiration rate (LCi analyzer, Li-Cor lnc., Nebraska, USA) were measured at 84 DAI and 141 DAI in full sunny days and between 9 to 12 am.

2.8. Statistical analysis Six treatments and its four replications were distributed in a completely randomized design in two years of field experiments. Statistical analysis was performed using SPSS software. The oneway analysis of variance (ANOVA) was used to test for significant differences among the treatment means and the Duncan’s multiple range test (DMRT) was used for pairwise comparisons. 3. Results and discussion Soil water content measured at 0–30 cm, 30–60 cm and 60–90 cm showed an increase with increasing soil depth and it decreased through time due to evapotranspiration. In all treatments, soil water content reached the initial value amount before next irrigation (data not shown). The soil water content in top soil layers (0–30 cm and 30–60 cm) of I4 and I5 increased comparing to initial value before irrigation, however, 20 days after supplemental irrigation application, the soil water content in treatment I4 reached the initial values as before irrigation. Mean soil volumetric water content for different treatments in depth of 0–90 cm is shown in Fig. 1 for two growing seasons (2010–2011 and 2011–2012). Soil water content in treatment I1 did not change remarkably comparing to before irrigation, as the soil water content was high even before irrigation due to winter rainfall. 3.1. Effective rainfall The maximum amount of effective rainfall was obtained for I3 and I1 and the minimum value was for I4 . The maximum amount of Reff /R ratio was obtained for I3 (Table 2). During winter, no irrigation water was applied and the rainfed condition was governed, hence there should be no difference between the soil water content and soil evaporation, and the difference that was observed might be due to spatial soil variation (Table 2). As shown in Table 2, nearly half of the rainfall (Reff /R = 0.54 as an average) was used by evaporation, which highlights the needs to pay more attention to reduce the soil evaporation in rainfed conditions. Khalili et al. (2001) showed a good correlation between effective rainfall and individual rainfall event for November through January; however, weak correlations were observed for February through April (in Badjgah, same location as in this study, during 1996–97 and 1997–98) due to increased temperature and higher evaporation rates. Similarly, the same result was observed in current study as the Reff measurement was carried out during winter when the air temperature was low (the mean minimum and maximum temperature were −3.4 and 12.3 ◦ C, respectively). 3.2. Estimation of actual crop evapotranspiration (ETa ) and soil evaporation In order to determine actual crop evapotranspiration using the soil water balance method (Eq. (1)), the following assumptions were considered. First, deep percolation was assumed to be zero as the grapevine root depth is high and the amount of applied water was not high. Second, runoff was considered to be zero as the irrigation method was basin irrigation. The total amount of crop evapotranspiration for I1 –I6 is shown in Table 3 during the growing

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Volumetric soil water content (%)

30 28 26 24 22

I1 I2

20

I3 I4

18

I5 I6

16 0

100

200

300

400

500

Days after the first soil water content measurement (20 Feb. 2011) Fig. 1. Variation of mean volumetric soil water content in depth of 0–90 cm during two growing seasons.

Table 2 Amount of rainfall (R), soil evaporation (E), effective rainfall (Reff ) and Reff /R ratio for all treatments during winter 2011–2012 (31 October 2011–15 March 2012). TreatmentsA

I1

I2

I3

I4

I5

I6

Average

R (mm) E (mm) Reff (mm) Reff /R

318.00 135.81 182.17 0.57

318.00 138.18 179.82 0.57

318.00 134.44 183.56 0.58

318.00 159.27 158.73 0.50

318.00 158.51 159.49 0.50

318.00 149.22 168.78 0.53

318 145.91 172.09 0.54

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ).

Table 3 Amount of irrigation, actual evapotranspiration (ETa ) and soil evaporation (E) during 2010–2011 (until 18 June 2011) and 2011–2012 (until 17 June 2012). Year 2010–2011 A

2011–2012

Treatments

Irrigation amount (1)

ETa (mm)

E (mm)

ETa (mm)

E (mm)

I1 I2 I3 I4 I5 I6

500 500 500 500 1000 0

285 b B 282 b 286 b 181 c 394 a 163c

100 130 121 72 173 62

257 b 248 b 211 c 140 d 364 a 131 d

101 100 66 35 156 42

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ). B Within columns, means which do not have superscript small letters in common are significantly different at P < 0.05.

season (from March to November) of 2010–2011 and 2011–2012. The amount of actual evapotranspiration was lower in the second year compared to first year due to lower amount of rainfall in March 2011. In both years, the ETa for I5 treatment was significantly higher than other treatments due to higher applied water and the lowest amount of ETa was determined for I6 treatments as it only depended on rainfall. Generally, the amount and rate of evaporation from soil surface measured by micro-lysimeter was high during grapevine growing season (Table 3). The rate of evaporation from soil surface during 2011–2012 was lower compared to 2010–2011 due to rejuvenation in 2007 and also higher canopy cover in 2011–2012. It was observed

that the evaporation rate was high after irrigation or rainfall event and it was very low after a period of drought. The significant highest and lowest ETa was for I5 and I6 , respectively. As shown in Table 3, the lowest E was obtained for I6 during 2010–2011 and for I4 during 2011–2012; whereas, the highest E was obtained for I5 in both growing seasons. The highest amount of ETa and E occurred in I5 treatment in both growing seasons due to higher applied water. The I6 treatment showed the lowest ETa and also E during 2010–2011 due to the fact that this treatment did not receive any irrigation water. Comparing the ETa and E of the second and first year indicated that the second year had lower values and this was mainly obtained because of lower amount of rainfall during the second year. Under rainfed conditions, the amount of rainfall might be at levels below full crop evapotranspiration (ETc ) throughout the growing season causing water deficits (Chaves et al., 2007). Supplemental irrigation might moderate water deficit by compensating some of ETc as it was also observed in this study. The combined effect of drought, high air temperature and high evaporative demand during summer in semi-arid areas has been studied widely (Chaves et al., 2007; Costa et al., 2007) and the result showed a decrease in grapevine yield.

3.3. Yield and dry matter Limited water supply during the berry cell division and cell expansion period declines berry enlargement, which, further, limits berry size and weight (Hardie and Considine, 1976; Merli et al., 2015a). Table 4 shows the berry weight and the mean weight of cluster in each vine for growing season of 2010–2011 and 2011–2012. The significant highest and lowest berries yield for 2010–2011 growing season was obtained in I3 and I5 , respectively; whereas, no significant difference was observed between other treatments and I3 and also with I5 . The highest cluster weight was 131.5 g obtained in I1 and the lowest was in I5 ; however, no significant difference was observed in cluster weight of I2 to I6 treatments. The same trend was observed in the second year compared with first year, as the significant highest and lowest berries yield was for I3 and I5 treatments, respectively. The obtained highest berries yield in I3 treatment might be due to the fact that supplemental

137

38

38

36

36

34

34

32

32 I1 I2

30

30

I3 I4 I5

28

Maximum air temperature (oC)

Green canopy temperature (oC)

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28

I6 Tmax

26

26 50

60

70

80

90

100

110

120

130

140

150

Days after first irrigation (DAI) Fig. 2. Variation of green canopy temperature for all treatments and maximum air temperature during 2010–2011 growing season.

Table 4 Berry yield and mean cluster weight for different irrigation treatments in 2010–2011 and 2011–2012 growing season. Year

2010–2011

TreatmentsA Berry yield (g vine−1 ) I1 I2 I3 I4 I5 I6

1143 ab B 2056 ab 2952 a 1037 ab 659.7 b 1066 ab

2011–2012 Cluster weight (g)

Berry yield (g vine−1 )

Cluster weight (g)

131.5 a 81.97 ab 89.08 ab 76.05 ab 58.04 b 64.39 b

1528 ab 2486 ab 2830a 2098 ab 442.4 b 1121 ab

62.19 b 93.46 ab 96.07 ab 104.2 a 91.46 ab 86.54 ab

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ). B Within columns, means which do not have superscript small letters in common are significantly different at P < 0.05.

irrigation during May provided enough water for grapevine plant to increase their berries yield in both year, as it coincided with the stage that grapevine berries start to enlarge its size. Whereas applying supplemental irrigation during other stages of growth was not very efficient. Treatment I5 showed the lowest berries yield in both years because that applying supplemental irrigation during March + April enhanced plant dry matter and; therefore, less water stored in soil for berries production. In general, low obtained berry yield was due to the recent drought in the experimental area and also due to the recent rejuvenated (3 years prior to this experiments) of grapes. The mean cluster weight of I1 was the lowest and for the I4 it was the highest in the second year; whereas, no significant difference was observed between I2 to I6 treatments. The berry yield comparison between first and second year indicated that the berry yield and mean cluster weight in second year increased by 16% and 6%, respectively (Table 4). Attalla et al. (2011) studied the effect of different amount of supplemental irrigation on olive production and they have found that the number of flowers under supplemental irrigation treatments were significantly higher than rainfed treatment; whereas, the amount of fruit drop under rainfed treatment were significantly higher. Different studies showed that

Table 5 Total dry mater including berries dry weight (TDW), leaf and branch dry weight (BDW) and shoot dry matter (SDW) for different irrigation treatments in 2010–2011. TreatmentsA

TDW (g vine−1 )

BDW (g vine−1 )

SDW (g vine−1 )

I1 I2 I3 I4 I5 I6

660.30 b B 875.27 ab 1044.09 a 711.09 b 812.36 b 409.71 b

291.80 b 464.10 a 453.60 ab 356.20 ab 276.20 b 349.00 ab

225.90 ab 182.20 ab 327.40 a 151.80 ab 120.40 b 160.70 ab

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ). B Within columns, means which do not have superscript small letters in common are significantly different at P < 0.05.

grapevine yield was not significantly reduced and quality of production may even increase under deficit irrigation strategies such as PRD (partial root drying) (Chaves et al., 2007; Dry et al., 2001). The latter was similar to result of this study as there was no significant difference between cluster weight I2 to I6 in the first year and between I1 to I5 in the second year. The highest total dry matter, TDW (including dry berries yield) during 2010–2011 was obtained in I3 and the lowest was in I6 ; whereas, no significant difference was observed between all treatments except I3 (Table 5). Shoot dry matter (SDW as the new growth of plant from the bottom in the each year, that is usually thinned to reduce water consumption and increase water use efficiency) in I5 was significantly lower than that in I3 as the highest (Table 5). The highest and lowest BDW (leaf and branch dry weight) was obtained in I3 and I5 . This result was similar to result of berries yield explained above. Bello (2008) showed that use of supplementary irrigation improved maize production by increasing fresh and dry grain weight and harvested plant stand and number of cobs. 3.4. Plant canopy temperature and leaf growth rate The first measurements of plant canopy temperature were made 7 days before irrigation event of I3 , as the bud formation stage was not completed yet and the plant did not have leaves (Fig. 2). As a consequence, no significant effect of the supplemental irrigation

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o

Leaf growth rate (mm d-1)

34

Maximum air temperature ( C)

36

8

6 32

4

30

I1 I2 I3

28

I4 2

I5 I6

26

Tmax 0

24 30

35

40

45

50

55

60

65

70

75

Days after first irrigation (DAI) Fig. 3. Variation of leaf growth rate in all treatments and and maximum air temperature in days during 2010–2011 growing season.

was observed between all treatments on first canopy temperature measurements. The maximum canopy temperature was mainly for I6 treatment, which did not receive any irrigation and it increased up to 34.21 ◦ C when the air temperature increased to 37 ◦ C. Generally, the canopy temperature of all irrigation treatments increased as the maximum air temperature (Tmax ) increased and it decreased as the Tmax decreased. The result in Fig. 2 shows that the supplemental irrigation can be effective in decreasing the plant canopy temperature only shortly after irrigation; whereas, it does not have significant effect on long-term plant canopy temperature reduction. Leaf growth rate during the three growing season is shown in Fig. 3. The first measurements of leaf growth were made 63 DAI. Leaf growth showed the same trend in all irrigation treatments, and it increased to maximum value at 71 DAI and then decreased continuously. Supplemental irrigation at different treatments had no significant effect on leaf growth, except at the beginning of growing season when the growth rate was significant in I3 and I5 . The maximum leaf growth rate was 7.1 mm d−1 for I3 and the minimum was 3.39 mm d−1 for I5 at 71 DAI. As it is shown in Fig. 3, the leaf growth increases as the Tmax declines and it decreases by increasing the Tmax . Although, I5 received more water as supplemental irrigation it showed the lowest leaf growth until 50 days after the first irrigation, the reason might be due to the fact of rejuvenation of vines for this treatment was done one year later compared to other treatments. Therefore, the vine root systems of this treatment might be still weak and most of water applied was used for soil evaporation rather than enhancing tree vegetative growth. It is also shown in Table 3 that the soil evaporation of the I5 was the highest compared to other treatments that might be due to lower vegetative growth of this treatment. The leaf growth of all treatments reduced about 60–70% in the third time of the measurements. Increase in leaf growth rate from 75 to 77 DAI was occurred as a result of increasing in air temperature. After 77 DAI, the leaf growth rate showed a decreasing trend in all treatments and until it reached zero. The decreasing trend occurred due to termination of leaf growth, at this stage most of the plant biomass is used for yield production. External leaf area of Godello and Treixadura irrigated vines with 50% of

Table 6 Leaf water potential (MPa) for different irrigation treatments during 2010–2011. TreatmentsA

Days after first irrigation 86

I1 I2 I3 I4 I5 I6

98

−1.65 −1.73 bc −1.74 bc −1.71 bc −1.49 a −1.81 c

bB

134

−1.99 −2.01 b −1.82 a −2.02 b −1.99 b −2.07 b b

141

−1.96 −2.04 a −2.01 a −2.05 a −1.93 a −2.03 a a

186

−1.91 −1.98 bc −1.95 bc −1.64 a −1.83 b −2.06 c bc

−1.79 a −1.90 a −1.74 a −1.75 a −1.73 a −1.74 a

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ). B Within columns, means which do not have superscript small letters in common are significantly different at P < 0.05.

ETc in a study of Trigo-Córdoba et al. (2015) were higher than rainfed treatments. Their results suggested that vine vegetative growth was stimulated by the water applied similar to what also reported by Intrigliolo and Castel (2010) for Tempranillo cultivar. 3.5. Crop physiological characteristics 3.5.1. Leaf water potential The first leaf water potential (LWP) measurements were conducted in 86 DAI, before application of supplemental irrigation for I3 treatment (Table 6). It was not possible to measure the leaf water potential earlier especially when applying I1 , I2 and I5 treatments, as the canopy did not have any leaves yet. The highest LWP was −1.49 MPa for I5 at 86 DAI and the lowest was −2.07 for I6 at 98 DAI. The result of leaf water potential measurement showed that the I6 treatment had significantly lower LWP especially compared with I5 during the growing season except for 98, 134 and 186 DAI when no significant difference was observed. Leuning et al. (2004) mentioned that when water supply declines, stomatal guard cells respond to leaf water potential, this is in line with the results of this study, where the I6 treatment showed the lowest leaf water potential and I5 showed the highest value. Grapevine stomata also strongly respond to plant water status, through hydraulic tensions developed in the xylem affecting leaf turgor (Chaves et al.,

M.M. Tehrani et al. / Scientia Horticulturae 202 (2016) 133–141 Table 7 Photosynthesis rate (␮mol m−2 s−1 ), stomatal conductance (mol m−2 s−1 ) and transpiration rate (␮mol m−2 s−1 ) during grapevine growth season for different irrigation treatments during 2010–2011. TreatmentsA

Photosynthesis rate (␮mol m−2 s−1 )

Stomatal conductance (mol m−2 s−1 )

Transpiration rate (␮mol m−2 s−1 )

Days after first irrigation

I1 I2 I3 I4 I5 I6

84

141

84

141

84

141

10.52 ab B 11.65 a 10.45 ab 9.74 ab 6.54 c 7.68 bc

6.96 b 9.23 b 6.82 b 12.10 a 7.43 b 7.36 b

0.128 a 0.133 a 0.110 a 0.103 a 0.093 a 0.115 a

0.068 b 0.100 ab 0.070 b 0.133 a 0.075 b 0.078 b

4.720 a 4.612 a 3.997 a 3.813 a 3.455 a 4.000 a

4.787 b 5.878 ab 4.790 b 7.315 a 5.222 b 5.288 b

A Supplemental irrigation during March (I1 ); during April (I2 ); during May (I3 ); during June (I4 ); during March + April (I5 ) and no supplemental irrigation (I6 ). B Within columns, means which do not have superscript small letters in common are significantly different at P < 0.05.

2010). Moreover, it has been demonstrated that a decline in leaf water potential of grapevine might enhances stomatal sensitivity to abscisic acid (Chaves et al., 2010). Trigo-Córdoba et al. (2015) conducted three years field experiments (2012–2014) to investigate the effects of rainfed and deficit irrigation (irrigated with 50% of estimated ETc ) on two grapevine cultivars leaf water potential. Their result showed that the LWP of rainfed vines were lower than deficit irrigation treatments during three years of field experiments. The LWP of rainfed treatments varied between −0.4 and −1.2 MPa for Godello cultivar; however, for Treixadura cultivar, it changed between −0.4 and −1.6 MPa. The minimum LWP of −2.075 MPa was observed in this study which is even lower than the values observed in the study of Trigo-Córdoba et al. (2015), which is because the latter experiment was conducted in temperate, humid with cool night and with annual rainfall of 900 mm. 3.5.2. Leaf stomatal conductance and photosynthesis rate The maximum amount of photosynthesis rate was 11.65 ␮mol m−2 s−1 for I2 and the lowest amount was 6.45 ␮mol m−2 s−1 at 84 DAI for I5 ; whereas, at 141 DAI the maximum value was 12.10 ␮mol m−2 s−1 for I4 which is significantly higher than the rest of treatments (Table 7). Dadbin et al. (2011) showed that supplemental irrigation at different times had no significant effect on vine photosynthesis and the reason might be that the amount of applied water could not compensate the water stress. Progressive reduction in photosynthesis rate (An ) by increasing drought in three grapevine cultivars (Khoshnave, Askari, Bidane-sefid) was observed with highest An value of 14.17 ␮mol m−2 s−1 for control treatments (soil water potential equal to −0.2 MPa) and Khoshnvae cultivar and minimum An value of 0.02 ␮mol m−2 s−1 for water stressed treatment (soil water potential equal to −1.5 MPa) and Bidane-sefid cultivar (Ghaderi et al., 2011). No significant difference was observed between stomatal conductance’s of different treatments at 84 DAI; whereas, at 141 DAI, I4 showed the highest value. Further, the results indicated that the LWP was minimum (−1.64 MPa) on 141 DAI as the vine was irrigated just before measurement, while the An and gs had the maximum value. Stomatal conductance of rainfed vine treatments were lower than those treated with deficit irrigation as shown by Trigo-Córdoba et al. (2015) for Godello and Triexaduara cultivars. The maximum and minimum values for gs of rainfed Godello cultivar during three years were ca. 1.2 and 0.2 mol m−2 s−1 , while for Triexaduara cultivar were 1.6 and 0.2 mol m−2 s−1 , respectively. The former measured gs values (Trigo-Córdoba et al., 2015) were greater that have observed in current study which might have been caused by enough soil water availability and a high relative humid-

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ity in the atmosphere. Under stress condition, plants closed their stomata and decreased its conductance (gs ) indicating crop need to higher water (Kramer and Boyer, 1995). The gradual decrease in An and gs values of almond with increasing water stress (at low water stress levels) is a response of drought-adapted plants (Rouhi et al., 2007). The latter was in line with the result of this study when comparing the decrease in grape An and gs of I2 compared with I6 . Supplemental irrigation showed no significant effect on transpiration rate at 84 DAI; however, irrigation at later stages, I4 showed the highest transpiration rate as 7.3 ␮mol m−2 s−1 and it reduced to 4.8 ␮mol m−2 s−1 for I1 (Table 7). Comparing the transpiration rate (Tr ) of 141 DAI and 84 DAI, the transpiration rate increased due to increase in air temperature, as a consequent stomatal conductance decreased following by decline in the photosynthesis rate (Table 7). Transpiration reduction under drought is one of the plant responses for water stress avoidance mechanism (Bacelar et al., 2007), as it was observed in I6 . Correspondingly, transpiration of three different grape cultivars (named Khoshnave, Askari, Bidane-sefid) decreased as drought increased (Ghaderi et al., 2011). Merli et al. (2015b) investigated that the level of water stress applied to Sangiovese grapevines before veraison should not be lower than 70% of daily vine water use, as further decline in water supply severely stressed vines and significantly reduced the An , gs , and LWP. In comparison with stomatal conductance, photosynthesis rates of grape when subjected to moderate water deficits generally declines at lower pre-dawn water potentials. As a consequence, intrinsic water use efficiency (A/gs or WUEi ) is usually higher in grapes under deficit irrigation (mild to moderate water deficits) than under well-watered conditions (Chaves and Oliveira, 2004; Gaudillère et al., 2002). Merli et al. (2015a) studied different series of WUE expressions (including the physiological and agronomical) and showed that WUEi increased significantly in water stressed Sangiovese vines compared to well watered ones, however the instantaneous WUE (An /Tr ) of vines was not significantly affected by water stress. Their results further confirmed that whole-canopy WUE was much better than single-leaf WUE, as whole-canopy WUE was calculated based on the entire leaf community without any artificial perturbation of natural leaf position. Comparison of the LWP and An (Tables 6 and 7) of I5 and I6 (as the treatments with the maximum and minimum applied supplemental irrigation) in 141 DAI showed that the effect of water stress on the LWP was more than the An , which could be a mechanism used by grape under water stress condition to lower LWP (by 12%), while had no significant effect on gs and An , indicating that the level of imposed stress was not enough to close stomata and decline An . Similarly, Liu et al. (1978) measured LWP of less than −1.6 MPa in field-grown ‘Concord’ vines; however, the leaves did not experience stomatal closure, concluding that the vines were not water-stressed enough. Grapevine photosynthesis is quite resistant to water stress (Chaves et al., 2007; Flexas et al., 2002) and it is generally considered a ‘drought-tolerant’ species by having control of stomatal over transpiration (Chaves et al., 1987; Schultz, 2003).

4. Conclusions Maximum amount of effective rainfall (Reff ) and Reff /R was obtained for I3 followed by I1 and I2 , that confirms the positive effect of supplemental irrigation during March, April and May. The maximum soil water content was obtained in March + April irrigation due to two irrigation events in the growing seasons. Leaf water potential increased over the growing season as the air temperature increased and it decreased at the end of growing season (186 DAI) as the temperature decreased and the crop water requirement also declined. The photosynthesis rate and stomatal

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conductance were higher for I1 , I2 and I3 at 84 DAI; however, all the values declined by ca. 30% at 141 DAI. Further, the photosynthesis rate and stomatal conductance of I4 and I5 at 141 DAI was approximately 1.2 times of at 84 DAI; whereas, there was no difference for I6 . The significant maximum berry yield was obtained for I3 (May supplemental irrigation) in both years indicating the fact that supplemental irrigation during May provided enough water for grapevine, as it is coincided with the stage where grape berries start to enlarge its size. Furthermore, no significant difference was observed between the photosynthesis rate and stomatal conductance of I3 and I5 (March + April supplemental irrigation) at 141 DAI, indicating the important time of applying water. Further, the effect of water stress (I6 : no supplemental irrigation) on lowering LWP was greater than gs and An , indicating that the level of stress imposed was not enough to negatively influence gs and An . It is concluded that supplemental irrigation during May produced more grape yield, although it received less water compared to two times of supplemental irrigation (I5 ). Acknowledgments The authors would like to acknowledge the financial support from Shiraz University and also the support by Center of Excellence for on-Farm Water Management and National Institute of Drought Research. They are also thankful to Mr. Ramezan Jafari for the technical help. References ˇ H., Tausz, M., Grill, D., Batiˇc, F., 2007. Detecting different levels of drought Sircelj, stress in apple trees (Malus domestica Borkh.) with selected biochemical and physiological parameters. Sci. Hort. 113, 362–369. Attalla, A., Abdel-Sattar, M., Mahrous, A., Abdel-Azeez, A., 2011. Olive trees productivity in response to supplemental irrigation under north-Western coastal conditions in Egypt. Am. Eurasian J. Agric. Environ. Sci. 11, 609–615. Bacelar, E.A., Moutinho-Pereira, J.M., Gonc¸alves, B.C., Ferreira, H.F., Correia, C.M., 2007. Changes in growth, gas exchange, xylem hydraulic properties and water use efficiency of three olive cultivars under contrasting water availability regimes. Environ. Exp. Bot. 60, 183–192. Bello, W., 2008. The effect of rain-Fed and supplementary irrigation on the yield and yield components of maize in mekelle, Ethiopia. Ethiop. J. Environ. Stud. Manage. 1, 1–7. Chaves, M., Oliveira, M., 2004. Mechanisms underlying plant resilience to water deficits: prospects for water-saving agriculture. J. Exp. Bot. 55, 2365–2384. Chaves, M.M., Harley, P.C., Tenhunen, J.D., Lange, O.L., 1987. Gas exchange studies in two Portuguese grapevine cultivars. Physiol. Plant. 70, 639–647. Chaves, M.M., Maroco, J.P., Pereira, J.S., 2003. Understanding plant responses to drought—from genes to the whole plant. Funct. Plant Biol. 30, 239–264. ˜ M., Rodrigues, M., Lopes, C., Chaves, M.M., Santos, T.P., Souza C.R. d. Ortuno, Maroco, J., Pereira, J.S., 2007. Deficit irrigation in grapevine improves water use efficiency while controlling vigour and production quality. Ann. Appl. Biol. 150, 237–252. Chaves, M., Zarrouk, O., Francisco, R., Costa, J., Santos, T., Regalado, A., Rodrigues, M., Lopes, C., 2010. Grapevine under deficit irrigation: hints from physiological and molecular data. Ann. Bot. 105, 661–676. ˜ M.F., Chaves, M.M., 2007. Deficit irrigation as a strategy to save Costa, J.M., Ortuno, water: physiology and potential application to horticulture. J. Integr. Plant Biol. 49, 1421–1434. Dadbin, M., Kamgar-Haghighi, A.A., Sepaskhah, A.R., Eshghi, S., 2011. Effect of supplemental irrigation on growth of dry-land grape in Badjgah region. 11th National Conference on Irrigation and Evaporation Reduction, 8. Dry, P.R., Loveys, B., Stoll, M., McCarthy, M., 2001. Strategic irrigation management in Australian vineyards. Journal International des Sciences de la Vigne et du Vin 35, 129–139. FAO, 2005 FAOSTAT. http://faostat.fao.org. FAO, 2006. Near East Fertilizer-use Manual. Food and Agriculture Organization of the United Nations, Rome, Italy (197 pp). Fageria, N.K., 1992. Maximizing Crop Yields. CRC Press. Flexas, J., Bota, J., Escalona, J.M., Sampol, B., Medrano, H., 2002. Effects of drought on photosynthesis in grapevines under field conditions: an evaluation of stomatal and mesophyll limitations. Funct. Plant Biol. 29, 461–471. Fooladmand, H., Sepaskhah, A., 2006. Probabilistic determination of microcatchment area for rain-fed tree cultures. Iran. J. Sci. Technol. Trans. B Eng. 30, 517–526. Gaudillère, J.P., Van Leeuwen, C., Ollat, N., 2002. Carbon isotope composition of sugars in grapevine, an integrated indicator of vineyard water status. J. Exp. Bot. 53, 757–763.

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