Partial rootzone drying (PRD) and regulated deficit irrigation (RDI) has been studied in many wine-producing countries as irrigation techniques, which improves.
Foliar Carbohydrate Content and Invertase Activity of ‘Syrah’ and ‘Moscato Canelli’ Vines Subjected to Partial Rootzone Drying and Regulated Deficit Irrigation B.F. Dantas, L. de Sá Ribeiro, S.R. de Sousa Luz, J.M.P. de Lima Filho, M.A.C. de Lima, C.R. de Souza and L.H. Bassoi Embrapa Tropical Semi Arid BR 428, km 152, C.P. 23 CEP 56302-970 Petrolina Pernambuco State Brazil Keywords: PRD, grapevine, metabolism, sugar, rootstock Abstract Partial rootzone drying (PRD) and regulated deficit irrigation (RDI) has been studied in many wine-producing countries as irrigation techniques, which improves the water use efficiency, vigor control and maturation quality of wine grape production without significant crop reduction. This work aimed to compare leaf starch, reducing sugars (RS) and total soluble sugars (TSS), as well as the activities of cell wall acid invertase (CWAI), vacuole acid invertase (VAI) and citosol neutral invertase (CNI), in PRD and RDI treated vines at the São Francisco Valley (Brazil). Leaves of ‘Syrah’ and ‘Moscato Canelli’ grafted in two rootstocks (1103 Paulsen and IAC 572) were sampled throughout the day (8:00, 12:00 and 16:00 h) at the flowering, veraison and ripe fruits at June, July and August/2004, respectively. The RDI treatment induced higher leaf starch and RS contents in ‘Syrah’ vines. For ‘Moscato Canelli’ vines there was no significant difference among treatments. At flowering, in June/ 2004, the leaf carbohydrate metabolism was lower, probably due to the phenological stage and to lower temperatures and radiation. On the other hand, leaf carbohydrate contents were higher at veraison in August/2004. Leaf starch accumulation was higher at 16:00 h and TSS and RS contents were higher at 12:00 h. No differences of CWAI, VAI, CNI activities were observed among treatments, except for RDI that induced higher CWAI activity in ‘Moscato Canelli’/’ 1103 P’. Carbohydrate metabolism in vines was influenced by temperature and phenological stages. More studies are necessary for conclusive results for PRD and RDI influence on vine leaves carbohydrate metabolism. INTRODUCTION The São Francisco Valley has been considered a new growing region for winegrape production. In this region, the wines have a typical taste and it is the unique wine produced in a tropical region. However, it is necessary to establish an adequate management for tropical vineyards to improve grape and wine quality. The key to improving winegrape quality in irrigated vineyards is to achieve an appropriate balance between vegetative and reproductive development, as an excess of shoot vigour have undesirable consequences for fruit composition. In recent years, deficit irrigation strategies as the partial rootzone drying (PRD), where water is applied to only one side of the root system, and the regulated deficit irrigation (RDI), where the irrigation is reduced in a defined period of the berry growth, have been proposed for managing grapevine growth and improving fruit quality (McCarthy, 1997). The PRD system is thought to rely on hormonal signals (abscisic acid, ABA) originating from the roots in response to low soil water potentials within the 'dry' zone (Stoll et al., 2000) and it has been well documented that PRD has the potential to reduce vigour, improve quality, maintain yield and improve water-use efficiency (Dry and Loveys, 1998; Loveys et al. 2000). However, the impacts of these irrigations strategies on leaf sugar metabolism as well as rootstock influence have not received much attention. A deep knowledge of the mechanisms that Proc. Intl. WS on Grapevine Eds. V. Nuzzo et al. Acta Hort. 754, ISHS 2007
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regulate leaf carbon allocation is of the great interest to use irrigation successfully, since the most of sugar synthesized in berries is derived from leaves. In this context, the aim of this study was to evaluate the diurnal and seasonal changes of leaf water potential, carbohydrates concentrations and invertase enzyme in leaves of field-grown grapevines submitted to PRD and RDI irrigation. Our approach may contribute to a better knowledge regarding the effects of water availability on grapevine physiology under semi-arid conditions. MATERIAL AND METHODS The experiment was conducted in an experimental field of Embrapa Tropical Semi-Arid, in Petrolina, Pernambuco State, Brazil. The two winegrape varieties of Vitis vinifera L studied were ‘Moscato Canelli’ and ‘Syrah’, both grafted on ‘IAC 572’ and ‘1103 P’ and planted in September 2000. The grapevines were spaced 3.0 x 1,5m and vertically trained. Experimental design for both cultivars consisted of a randomized block design with two factors (irrigation and rootstock) and 5 replicates of 9 grapevines per treatment. PRD treatment irrigation system had two drip tubes, one in each side of the plant row, and water was applied alternating each 14 days to only in one side of the rootzone, allowing other half to dry; it was imposed at 47 days after pruning – dap, after the fruit set. RDI treatment had one drip tube per plant row and it was imposed at 91 dap, after veraison. Soil humidity was kept around 60% by more 4 water applications at 103, 107, 110 and 144 dap. The term full irrigation (FI) is being used just to specify the time period before the two irrigation treatments imposition. The irrigation scheduling was performed based on tensiometers installed at 0.2, 0.4, 0.6, 0.8 and 1.0m depth, and frequency ranged from 3 to 5 times per week. The gross amounts of applied water were 1463.3 and 1200 m3.ha-1 in RDI and PRD, respectively. All evaluations were carried out throughout the day at the flowering, veraison and ripe fruits at June, July and August/2004, respectively. Plant water status was monitored by measuring leaf water potential (ΨL), in three previously marked grapevines of each block, throughout the day and the season using a Scholander-type pressure chamber. During the trial nine exposed leaves collected from the main shoots of three previously marked grapevines were sampled for carbohydrate metabolism analysis. The diurnal and seasonal changes of leaf carbohydrates were analysed through quantification of starch (Allen et al., 1977), total soluble sugars (Yemm and Willis, 1954), sucrose and reducing sugars (Miller, 1959). The enzymatic activities of citossolic, vacuolar and wall invertase were measured following Nascimento et al (1998). RESULTS AND DISCUSSION The Fig. 1 shows the diurnal and seasonal changes in ΨL measured in both cultivars in sunny days during the different phenological stages. The irrigation treatments and rootstocks did not influence the leaf water status in both cultivars. A similar pattern of the ΨL was observed in both cultivars. However, at midday, the ΨL in ‘Moscato Canelli’ reached lower (around -1.5MPa) values than in ‘Syrah’ (around -1.2MPa). There were no significant differences between PRD and RDI treatment as shown in figure 1c,f. The main PRD effect on leaf water status has been attributed to reduction in stomatal conductance (gs) due to increase of ABA xylem as showed in the experiments where PRD is compared to a control where the double of water is applied (Stoll et al., 2000). However, in this study, which there were small differences in soil water deficit between PRD and RDI (data not shown), the leaf water potential was similar in both deficit irrigation strategies. The regulation of PRD is very subtle when compared to other deficit irrigation treatment as recently showed by Souza et al., 2005. There was an increase of leaf starch concentration during the growing season as illustrated in Fig. 2. Under full irrigation conditions at bloom stage, the diurnal pattern showed low starch concentrations in leaves of both cultivars and rootstocks as compared to the other phenological stages (Fig. 2a,d). The rootstock did not affect leaf starch throughout the day in all phenological stages. However, there were significant differences 302
between irrigation treatments. The leaf starch concentration was higher in leaves of both cultivars and rootstocks at the end of the day under RDI than in PRD treatment (Fig. 2 c,f). This response could be related to increased photosynthesis and/or reduction in starch translocation in leaf of grapevines growing under RDI conditions. The total soluble sugars (TSS) also increased during the growing season in both cultivars (Fig. 3). However, the significant differences only occurred during the ripening period, where the combination ‘Syrah’/’IAC 572’ under PRD showed significant reduction in leaf TSS as compared to others treatments (Fig. 3c). The rootstock and deficit irrigation treatments did not effect diurnal and seasonal changes of reducing sugars (Fig. 4). Although the mechanisms of sucrose unloading is still unclear in leaves and fruits of grapevines, it is currently believed that invertases enzymes play a major role in converting imported sucrose to hexose (Ruffner et al.,1990). In this study, no definite diurnal pattern was found for activity of invertases, which remained approximately constant during the day (Fig. 5,6,7). There was only significant increase in activity of cell wall invertase (CWI) in leaves of ‘Moscato Canelli’ grafted on ‘1103 P’ compared to ‘IAC 572’, and both combination (scion/rootstock) showed the lowest activity under PRD treatment when compared to RDI. Regarding the seasonal evolution, although Dantas et al. (2005) verified that invertase activity increases during fruit maturation, only vacuolar acid invertase (VAI) showed a slightly increase during the growing season. Furthermore, the increase in reducing sugars was better correlated with VAI activity than with others invertase enzymes (data not shown). The vacuolar invertase has been considered the main enzyme involved in hydrolysis of sucrose in leaves and grape berries (Hunter et al., 1994; Davies and Robinson, 1996). However, the CWI may be also a key factor in determining sink strength in the plants with sucrose as a main translocated sugar in phloem (Zhang et al., 2001). According to these authors, the CWI may be involved in sucrose unloading through apoplasmic pathway in apple fruit. In general terms, the deficit irrigation treatment had no negative impact on the most biochemical analyses of field grown grapevines under semi-arid conditions. Although both irrigation strategies may be useful for irrigation purpose, more studies at physiological and biochemical levels are needed for successful of the controlled irrigation programs in field-grown grapevines in São Francisco River Valley. ACKNOWLEDGEMENTS The authors would like to thank Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and Banco do Nordeste do Brasil (BNB) for financial support and fellowships provided. Literature Cited Allen, S.E., Grimshaw, H.M., Parkinson, J.A. and Quarmby, C. 1977. Chemical analysis of ecological materials. Blackwell Scientific, Oxford. Dantas, B.F., Ribeiro, L.S. and Luz, S.R.S. 2005. Foliar carbohydrates content and invertase activity in vines at São Francisco River Valley - Brazil. Rev. Brasileira Frut. 27: 198-202. Davis, C. and Robinson, S.P. 1996. Sugar accumulation in grape berries. Plant Physiol. 111:275-283. Dry, P.R. and Loveys, B.R. 1998. Factors influencing grapevines vigour and the potential for control with partial rootzone drying. Australian J. Plant Physiol. 4:140-148. Hunter, J.J., Skrivan, R. and Ruffner, H.P. 1994. Diurnal and seasonal physiological changes in leaves of Vitis vinifera L.: CO2 assimilation rates, sugar levels and sucrolytic enzyme activities. Vitis. 33:189-195. Kriedemann, P.E. and Smart, R.E. 1971. Effect of irradiance, temperature and leaf water potential on photosynthesis of vine leaves. Photosynthetica. 5: 6-15. Loveys, B.R., Dry, P.R., Stoll, M. and Mccarthy, M.G. 2000. Using plant physiology to 303
improve the water efficiency of horticultural crops. Acta Hort. 537:187-197. McCarthy, M.G. 1997. The effect of transient water deficit on berry development of cv. Shiraz (Vitis vinifera L.). Australian J. Grape and Wine Res. 3:102-108. Miller, G.L. 1959.Use of dinitrosalicylic acid reagent for determination of reducing sugars. Analyt. Chem. 31:426-428. Nascimento, R., Mosquim, P.R., Araújo, E.F. and Santanna, R. 1998. Distribuição de amido, açúcares solúveis e atividades de invertases em explantes de soja sob várias concentrações de sacarose e diferentes fontes de nitrogênio. Revista Brasileira de Fisiologia Vegetal. 10:125-130. Souza, C.R., Maroco, J.P., Santos, T., Rodrigues, M.L., Lopes, C., Pereira, J.S. and Chaves, M.M. 2005. Control of stomatal aperture and carbon uptake by deficit irrigation in two grapevines cultivars. Agri. Ecosys. Environ. 106:261-274. Souza, C.R., Maroco, J.P., Santos, T., Rodrigues, M.L., Lopes, C., Pereira, J.S. and Chaves, M.M., 2003. Partial rootzone-drying: regulation of stomatal aperture and carbon assimilation in field grown grapevines (Vitis vinifera cv Moscatel). Funct. Plant Biol. 30:653-662. Stoll, M., Loveys, B. and Dry, P. 2000. Hormonal changes induced by partial rootzone drying of irrigate grapevine. J. Exp. Bot. 51:1627-1634. Yemm, E.W. and Willis, A.J. 1954. The estimation of carbohydrates in plants extracts by anthrone. Biochem. J. 57:508-514. Zhang, D.P., Lu, M.Y., Wang, Y.Z., Duan, C.Q. and Yan, H.Y. 2001. Acid invertase is predominantly localized to cell wall of both the practically symplasmically isolated sieve element/companion cell complex and parenchyma cells in developing apple fruits. Plant Cell Environ. 24:691-702. Figurese 0.0
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Fig. 7. Cytosolic neutral invertase activity in leaves of ‘Syrah’ (PS a, b, c) and ‘Moscato Canelli’ (MC, d, e, f) vines, on rootstocks (1103 Paulsen and IAC 572) and irrigation strategies (PRD, partial rootzone drying; RDI, regulated deficit irrigation; FI, fully irrigated plants before PRD and RDI treatments) during the phenological phases: bloom (a,d), veraison (b, e) and ripe fruits (c, f).
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