Thermoluminescence (TL) glow curves were recorded from leaves of eight Vitis varieties grown in South-West India, viz. Thompson Seedless, Sonaka, Anab-E-Shahi, Kishmish Chami, Tas-A-Ganesh, Black Monuka, Bangalore Purple and American Dogridge belonging to the Vitis vinifera, V. labrusca and V. champini species. The TL peaks were analysed, using a computer-assisted model based on the general order kinetics theory, to determine thermodynamical parameters such as activation energy, entropy, frequency factor and free energy. It was observed that all six V. vinifera samples showed an entirely different TL pattern consisting of only one prominent and highly narrow peak at around -5 °C (peak II). The prominance oft this peak attributed to S2/S3 Qa· recombination suggests a modification at the plastoquinone electron acceptor sites. On the other band, the remaining two varieties Bangalore Purple and American Dogridge showed broader TL spectra consisting of a higher number of peaks. This basic difference is attributed to the difference in species of the selected varieties. Moreover, the TL recorded from Bangalore Purple resembled the standard TL spectra of spinach. The study undertaken in this paper may be relevant in grape breeding programs

Noitsakis, B.

Patakas, A.

Stavrakas, D.

English

JKI Open Journal Systems (Julius Kühn-Institut)

Vitis 36 ( 1 ), 11-14 (1997) Adaptation of leaves of Vitis vinifera L. to seasonal drought as affected by leaf age by 1) Labaratory of Viticulture , Aristotle University of Thessaloniki, Thessaloniki, Greece 2) Department of Range and Wildlife Science, Aristotle University of Thessaloniki, Thessaloniki, Greece 3) Labaratory of Viticulture, Agricultural University of Athens, Athens, Greece S u m m a r y : The airri of this study was to evaluate the water, turgor, osmotic potentials and Ieaf water content during leaf ontogeny using both the pressure vo)ume and the psychrometric techniques. The symplasmic water fraction of the total water content decreased with leaf age from 78 % in immature Ieaves to 62 % in old Ieaves. The capability for osmoregulation was almost the same in immature and mature leaves but decreased in old Ieaves. The volumetric modulus of elasticity (E) was Iower in immature Ieaves (12.7 MPa) and increased in mature (22.5 MPa) and old Ieaves (28 MPa). The high elasticity of young leaves seems tobe an important strategy for adaptation to drought. K e y w o r d s : Ieaf ontogeny, osmoregulation, tissue elasticity, water relations, water stress. Introduction The majority of vines grown in Mediterranean coun-tries are not irrigated and thus they are usua11y exposed to conditions of water stress in summer. The most obvious effect even of mild water stress is reduced growth. Cell enlargement which is particularly sensitive to water defi-cits (HsrAo et al. 1985; ScHULZE 1986) depends on turgor pressure (P) and the expansion rate was shown to be pro-portional to the extent of P over a threshold value (JONES 1986). Turgor pressure can be maintained by two strate-gies: 1) lowering of the osmotic potential (ll) by osmoti-cally active solutes or 2) increase of the elasticity of cell walls (for grapevines: DüRING 1984; ScHULTZ and MATTHEWS 1993; DüRING and DRY 1995). There is some evidence that the type and relative importance of these strategies vary among species or even within a species (PARKER and PALLARDY 1985), as well as with physiological leaf age (PATAKAS, unpubl.). The objectives of this study were to use both the pres-sure volume and the psychrometric technique to evaluate adaptational processes ofleaves during the season to drought stress. Material and methods Ten-year-old field-grown grapevines (Vitis vinifera L. cv. Roditis) grafted on 110 Richter CV. rupestris x V. berlandieri) rootstocks near the experimental station of the University of Thessaloniki were used. According to their age leaves were classified in 4 groups: 18-d-old still expanding young leaves (L1); 35-d-old fully ex-panded, mature leaves (L2); 80-d-old mature leaves (L3); 120-d-old leaves without any signs of senescence (L4). Irrigation had not been applied and no rainfall was re-corded 5 weeks be-fore and during the experiment. The experimentwas repeated 4 x in August 1994. No signifi-cant differences between measurements on single days were obtained. Predawn leaf water potential of 3 mature leaves (L2) was measured using the psychrometric technique (WILSON et al. 1979). Measurements were made at 10-d-intervals starting in May 1994. Diurnal changes of leaf conductance to water vapour (Cw) were determined on 7 leaves per age group. Cw was measured approximately hourly from 06.00 to 20.00 h us-ing a steady state porometer (Li-1600, Li-Cor, Nebraska, USA). Leaf water potential (\jl) as weil as the osmotic poten-tial (TI) were measured hourly from 06.00 to 18.00 h on 5 leaves per age group using the psychrometric technique (WILSON et al. 1979). Three pairs of 6 mm discs were punched from each leaf. The first pair of discs was used for the determination of the leaf water potential while the second was used for measurements of the osmotic poten-tial (KmoE et al.1991 ). Turgor potential was calculated as the difference between 'V and rr. Concomitant measurements of the relative water con-tent (RWC) were made on the third pair of discs obtained from the same leaf that was used for the determination of the water potential components. After determination of fresh weight (FW), leaf discs were placed in distilled wa-ter for 10 h and the turgid weight (TW) was measured. The discs were then dried at 80 °C for 24 h and their dry weight (DW) was recorded. According to KoiDE et al. (1991) RWC of leaves was calculated by the formula: FW-DW RWC = x 100 (1) TW-DW The net solute increase in leaves of different age groups was calculated relating n to water volume (Vw) (HsrAo et al. 1985): n = RTnJ(Vw) (2) where ns is the number of moles of solutes, R the gas con-stant and T the absolute temperature. Changes in water potential components in relation to a relative lowering of symplasmic water (RLSW) were de-Correspondence to: Prof. B. NotTSAKts, Department ofRange and Wildlife Science, Aristotle University ofThessaloniki, P.O. Box: 236, Thessaloniki, Greece. Fax: (31) 998886. 12 A. PATAKAS, B. NoiTSAKIS and D. STAVRAKAS termined on 5 leaves per age group using the pressure cham-ber (SCHOLANDER et al. 1964; CHEUNG et al. 1975). RLSW was calculated as water loss expressed as percentage of the symplasmic water content at full turgor (W 0), i.e. W-W 0 RLSW = --- x 100 (3) wo where W 0 is calculated from the intercept of the straight part ofthe pressure-volume curve with the abscissa (TYREE and KARAMANOS 1980) and W is the actual weight of symplasmic water after pressurization. The bulk modulus of elasticity (E) was calculated ac-cording to TURNER (1981): E = I:!.PI!.WJ!!.W (4) The value of e obtained near maximum turgor (Emax) of leaves at different ages was compared. Changes in the symplasmic water fraction (SWF) as a percentage of the total water content were calculated ac-cording to PAVLIK (1984): wo SWF = --- x 100 (5) TW-DW Results Predawn \jl values declined continuously from -0.25 MPa in May to -0.55 MPa in August. Diurnal changes of \jl vs. RWC for allleaf ages are shown in Fig. 1. Young leaves (L1) presented lower RWC values at 0600 h than mature and old leaves ( L2, L3, L4). The decrease in RWC tended to be smaller in old leaves (L4) compared to young leaves (L). Furthermore young leaves exhibited lower values of RWC at the same value of \jl. In allleaves the \jl value at 06.00 h (-0.6 MPa) was similar tothat at 15.00 h; it decreased to about -1.4 MPa in both mature and young leaves and to -1.1 MPa in old leaves. Old leaves (L4) had a lower stomatal conductance than mature (L2, L3) and young leaves (L1) regardless of the time of day (Fig. 2). Stomatal closure seemed to start at higher values of 'I' (-0.85 MPa) in old leaves compared to mature leaves ( -1.3 MPa). The symplasmic water fraction (SWF) decreased with leaf age from ca. 78 % in young leaves (L1) to ca. 62 % in old leaves (L4) (Table). Significant changes in 'I' and its components, P and n, were observed during leaf ontogeny (Fig. 3). In particular, n at full turgor (llo) decreased with leaf age .from -1.35 MPa in young leaves (L1) to -1.5 MPa in L2, -1.6 MPa in L3 and to -1.7 MPa in L4 leaves. Also the RLSW values at incipient plasmolysis (i.e. at P=O) decreased during leaf ontogeny from 17 % in young leaves to 11.2 % in old leaves indicating more rigid cell walls. Furthermore, changes of dP vs. dRLSW seem to be lower in young compared to mature and old leaves. Thus, for a 5 % water loss dP was 0.58 MPa in L 1 leaves compared to 0.86 MPa in L2, 1.01 MPa in L3 and 1.19 MPa in L4 leaves. The e value at full turgor (Emax) increased significantly with leaf age from 12.7 MPa in young leaves to 22.5 MPa 1 L1 L2 ~ ~0 0 0.5 -: ~ :! c !!! •1. 0 .. 1 ~ ~ . 5 u -0.5 0.5 ~ -~ ··-'--.a 1 1 L3 L4 .Ii ö ~ 0. 5~ 0 0 ~ 0.5 5 ~ :~ ·0. ·1 t281808Q88878885 QSQ4Q3Q2Q11108Q88 R.W.C ('llo) ..... wat.r potential-+ turoor potential -4- oemollc potenttaJ ·1 Fig.l: Leaf water potential components in relation to relative water content (RWC) of leaves differing in their age. Bars indi-cate the standard error of the mean of 5 replicates. LI' L2, L3, 00.5 Cl> ~ E () 0.4 -Cl> () c:: ~ 0.3 () ~ "0 c:: 0 () 0.2 CU -CU g 0.1 -(/} L4: see Table. o+-------.------.-------.------.--J -1.6 -1.3 -1 -0.7 -0.4 Water Potential (MPa) --a- L 1 ........_ L2 --9- L3 -a- L4 Fig. 2: Diurnal changes in stomatal conductance in relation to the water potential of leaves differing in their age. Bars indicate the standard error of the mean of 7 replicates. LI' L2, L3, L4: see Table. and 25 MPa in L2 and L3 leaves (Table). Old leaves (L4) showed even higher Emax values of 28 MPa. Adaptation to seasonal drought 13 Tab I e Values of symplasmic water fraction (SWF), relative lowering of symplasmic water (RLSW) and bulk modulus of elasticity (Emax) of leaves differing in their age. Different letters within columns indicate significant differences at the 5% Ievel. L1: young Leaf age LI Lz L3 L4 leaves; L2, L3: mature leaves; L4: old leaves (see Material and methods) SWF (%) RLSW (%) Emax (MPa) 78 a 17 a 12.7 a 69 b 14.5 b 22.5 b 66 b 12 c 25 b 62 c 11.2 c 28 c L.S.D (a=0.05) 3.21 1.43 2.72 L1 L2 'ii' ~ ~ t:;i 11? 10 15 10 15 RLSW(%) 1.5 0.5 1.5 0.5 Fig.3: Changes in water potential ('Jf), osmotic potential (TI), and turgor potential (P) in relation to relative lowering of sym-plasmic water (RLSW) of leaves differing in their age. L1, L2, L3, L4: see Table. The diumal decrease of n as affected by water loss tended to be greater in young and mature leaves compared to old leaves (Fig. 1). A more detailed description of os-motic changes requires a distinction between changes due to the removal of water from the tissue symplasm ("con-centration effect") and those due to an accumulation of solutes. Comparing the net increase of solutes in leaves of different age, the ability of the leaves to osmoregulate can be deterrnined (HSIAO et a/. 1985; NOITSAKIS and TSIOUVARAS 1990). The calculated net increase of solutes in cells was significantly higher in mature (16 %) and young leaves (14 %) than in old leaves (1.8 %). Discussion About 31-34 % of the water in mature leaves is lo-cated outside the plasmalemma. The values reported for a number of species using the pressure-volume technique have all been in the range from 5 to 45 % (Vos and ÜYARTZUN 1988; ANDERSEN et al. 1991 ). Values of the apoplasmic and symplasmic fractions seem to be strongly related to leaf age. Fully expanded and old leaves showed significant lower values compared to young leaves both in the symplasmic water fraction and in the fraction of water lost to reach turgor zero (Table). This suggests that water moves out from the symplasm into apoplasm as leaves get older. This change in the allocation of water will increase the concentration of solutes in the symplasm and therefore will result in a decrease of n even without changes of the amount of net solutes. This suggestion would explain the lower values in "' and n at full turgor and along the whole range of tissue dehydration to turgor zero of mature and old leaves (Fig. 3). Of greater interest are the diurnal changes in n which are quite large in mature and young leaves when measured by thermocouple psychrometry (Fig. 1). The diurnal re-duction in osmotic potential was not only due to a passive "concentration effect" as cell water decreased but it was also due to an accumulation of solutes. The accumulation of solutes in old leaves was very low. These results indi-cate that the ability to osmoregulate is reduced with in-creasing leaf age (SMART and CooMBE 1983, DüRING 1984). Compared to mature and young leaves older leaves (L4) showed higher RWC values. This can be attributed to their significantly lower transpiration rates (Fig. 2). Simi-lar results were reported for various plant species (DuFRENE and SAUGIER 1993). In addition, stomatal closure started at higher values of 'I' in old leaves thereby restricting water loss effectively, a fact that contributes to turgor mainte-nance under water stress conditions. We expected that the higher RWC values in mature leaves (L2, L3) compared to young leaves (L1) were due to reduced stomatal conductance (Fig. 1). However, mature leaves exhibited higher stomatal conductance than young leaves (Fig. 2). This response might be explained by the greater changes in 'I' probably due to greater changes in P and/or n. Since the ability to osmoregulato was almost the same in mature and young leaves, the greater changes in 'I' in mature leaves could be attributed to the higher changes in P in relation to water loss. Assuming that the elasticity of cell walls determines the rate of change in turgor pres-sure in relation to water loss, higher values of E in mature leaves are responsible for the higher changes in P in rela-tion to relative symplasmic water loss. Cell wall rigidity increased almost 2-fold from an in-termediate stage of leaf development (L1) to leaf maturity (L2, L3). This considerable increase of E could be inter-preted as a physiological mechanism which enables the mature vine leaves to change rapidly their water potential (high d'lf) in response to small leaf water Iosses (low dRWC). Furthermore, the drastic decrease in 'I' in mature leaves could help to maintain water uptake from drying 14 A. PATAKAS, B. NOITSAKIS and D. STAVRAKAS soil without undergoing a large tissue water deficit (ABRAMS and MENGES 1992). Conversely, young vine leaves are characterized by more elastic cell walls. Lower E in young leaves resulted in the maintenance of a positive cell turgor at lower values of leaf water content than in mature leaves. The mainte-nance of turgor in still expanding leaves is very important for plant growth (BOYER 1988; MATSUDA and RAYAN 1990). The higher cell wall elasticity of young leaves enables the vines to maintain a positive pressure in cells, large enough to sustain enlargement and thus plant growth under mild water stress conditions. References ABRAMS, M. D.; MENGES, E. S.; 1992: Leaf ageing and plateau effects on seasonal pressure volume relationships in three sclerophyllous Quercus species in south eastem USA. Functional Ecol. 6, 353-360. ANDERSEN, N.; 1ENSEN, R.; LOSCH, R.; 1991: Derivation ofpressure vo!ume curves by a non-linear regression procedure and determination of apoplastic water. 1. Exp. Bot. 42, 159-165. BaYER, 1. S.; 1988: Cell enlargement and growth -induced water potentials. Physiol. Plant. 73,311-316. CHEUNG, Y. S.; TYREE; M. T.; DAINTY, J.; 1975: Water relations parameters on sing1e leaves obtained in a pressure bomb and some ecological interpretations. Can. 1. Bot. 53, 1342-1346. DüRING, H.; 1984: Evidence for osmotic adjustment to drought in grape-vines (Wtis vinifera L.). Vitis 23, 1-10. --;DRY, P. R.; 1995: Osmoregulation in water-stressed roots: Responses of leaf conductance and photosynthesis. Vitis 34, 15-17. DuFRENE, E.; SAUGIER, B.; 1993: Gasexchange in oil palm in relation to light, vapour pressure deficit, temperature and leaf age. Functional Ecol. 7,97-104. HsrAo, T. C.; SILK, W. K.; 1ING, 1.; 1985: Leaf growth and water deficits: Biophysical effects. In: BAKER, N. R.; DAVIES, W. 1.; ÜNG, C. K. (Eds.): Control of Leaf Growth, 239-266. Univ. Cambridge. JoNES, H. G.; 1986: Plantsand Microclimate. Univ. Cambridge, 213-223. KomE, R. T.; RosrcHAUX, R. H.; MoRsE, S. R.; SMITH, C. M.; 1991: Plant water status, hydraulic resistance and capacitance. In: PEARCY, R. W.; EHLERINGER, 1.; MooNEY, H. A.; RuNDER, P. W. (Eds.): Plant Physio1ogi-cal Eco1ogy, 161-183. Chapman and Hall, London, New York. MATSUDA, K.; RAYAN, A.; 1990: A key factor regu1ating plant tissue re-sponse to water stress. In: KATTERMAN, F. (Eds.): Environmental In-jury to Plants, 63-87. Academic press. NorTSAKIS, B.; TsrouVARAS, C.; 1990: Seasona1 changes in components of leaf water potential and 1eaf area growth rate in kermes oak. Acta Oeco1ogica 11, 419-427. PARKER, W. C.; PALLARDY, S. G.; 1985: Genotypic variation in tissue water relations of leaves and roots of b1ack wall nut (lug/ans nigra) seed-lings. Physiol. Plant. 64, 105-110. PAVLIK, B. 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Plant and Soil 58, 339-366. TYREE, M. T.; KARAMANOS, A. 1.; 1980: Water stress as an ecological factor. In: GRACE, 1.; FoRD, E. D.; 1ARVIS, P. G. (Eds.): Plantsand their Atrnos-pheric Environment, 237-261. Blackwell, Oxford. Vos, 1.; ÜYARTZUN, 1.; 1988: Water re1ations of potato leaves. li. Pressure vo1ume analysis and inferences about constancy of the apoplastic fraction. Ann. Bot. 62, 449-454. WrLSON, 1. R.; FrsHER, M. J.; ScHULZE, E. D.; DoLBY, G. R.; Luoww, M. M.; 1979: Comparison between pressure-volume and dew point-hygro-metry techniques for determining water relations characteristics of grass and Iegurne leaves. Oecologia 41, 77-88. Received May 23, 1996 Vitis 36 (2), 102 ( 1997) In the paper Erratum Adaptation of leaves of Vitis vinifera L. to seasonal drought as affected by leaf age by A. PATAKAS, B. NoiTSAKIS and D. STAVRAKAS Vitis 36 (1), 11-14 (1997) the term "Relative lowering of symplasmic water (RLSW)" (see text, Table and Fig. 3) was misnamed and should be replaced by "Relative symplasmic water loss (RSWL)". 

Adaptation of leaves of Vitis vinifera L. to seasonal drought as affected by leaf age

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Adaptation of leaves of Vitis vinifera L. to seasonal drought as affected by leaf age

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