Sap flow measurements in grapevines (Vitis vinifera L.) 1. Stem morphology and use of the heat balance method

The heat balance method was evaluated in detail for its use in older, mature grapevines with stems of 35 – 45 mm in diameter. Dye colouring of the xylem vessels revealed that even 21 year old grapevines did not show any development of heartwood and that xylem vessels of that age still have the capacity to transport water. A comparison of weight loss of potted vines on a balance and sap flow measurements demonstrated that the heat balance system reflected rapid changes in flow rate without any time delay. However, since even 20 year old xylem vessels of grapevines have the capacity to conduct water, the heater band was not able to heat the sap in all year rings evenly. Apparently, at low flow rates this effect was small and sap flow was calculated correctly. With increasing flow rates large thermal heterogeneities developed upsetting the calculation of the heat balance and mass flow. Consequently, actual sap flow was overestimated by 50 to 100% at high flow rates. This could be attributed to thermal gradients in these relatively thick stems excluding the use of this technique for measurements of long term as well as short term water use patterns in older grapevines. This revised version was published online in June 2006 with corrections to the Cover Date.     

应用Granier热消散探针(TDP)法测定树木的木质部液流:理论与实践

Granier热消散探针法是目前研究树木生理生态和森林水文最常用的测定整树水分利用的方法之一.然而,已有的相关综述文献中,还没有专门介绍利用Granier热消散探针研究木质部液流的综述文章.本文重点介绍了Granier热消散探针测定系统的理论基础,对有关该探针的校准和改进的最新研究进展进行了综述,并还深入探讨了零液流信号值的确定、自然热梯度、损伤效应、液流的逆格型和将木质部液流密度外推至整树蒸腾耗水量等重要的实际问题.     

Vessel-diameter distribution in roots of grapevines (Vitis vinifera L. cv. Shiraz)

The distribution frequency patterns of diameter of xylem vessels and percentage of total predicted axial conductances were studied in 190-day and 212-day-old main roots of grapevine (Vitis vinifera L. cv. Shiraz) grown under well-watered and stressed conditions. The protoxylem were the first to mature and were responsible for most of the theoretical conductance in root segments between the tip and 2.5 cm from the tip. Some large xylem vessels retained cross walls and protoplasm up to 22.5 cm from the tip. Statistical tests using the Kolmogorov-Smirnov two sample test showed that the pattern of distribution frequency of xylem vessels classified in different diameter classes varied with distance from the root tip. The distribution frequency of xylem vessels was similar in both well-watered and stressed plants from the tip up to 15 cm from the tip. At distances further from the tip the distribution frequency of xylem vessels of well-watered plants was significantly different from that of stressed plants, with the former having more larger vessels than the latter. The pattern of vessel distribution frequency was different from that of percent total axial conductance (K_h) predicted with fewer large vessels carrying most of the axial flow.     

一种测定葡萄木质部压力梯度的新方法

通过同时测定葡萄木质部导管液流平均流量和流速,应用变形的哈根-泊萧叶方程,研究了测定葡萄木质部压力梯度的新方法。结果表明,在直径分别为7mm的葡萄茎段和4mm的葡萄叶柄上,用此新方法测得的木质部压力梯度与实际加在其上的压力梯度吻合的很好,说明此新方法可用于连续、实时测定葡萄木质部压力梯度。用此新方法在离体葡萄枝上测定发现,随光照强度增强,其木质部压力梯度成线性正相关增加。     

ABA xylem concentrations determine maximum daily leaf conductance of field-grown Vitis vinifera L. plants

Differences in maximum leaf conductance in grapevine plants growing in soils with contrasting water availabilities during mid-summer in Portugal could be accounted for by differences in the concentration of ABA in xylem sap. This conclusion is reinforced by the observation that the relationship between leaf conductance and endogenous ABA concentration can be mimicked by the application of exogenous ABA to leaves detached from irrigated plants. During the day, leaf conductance decreased after a morning peak, even when the leaves remained in a constant environment at a moderate temperature and leaf-to-air vapour pressure difference. This decline in leaf conductance was not a consequence of an increase in the xylem ABA concentration or the rate of delivery of this compound by the transpiratory stream. The afternoon depression in leaf conductance was associated with an apparent limitation in stomatal opening potential, which persisted even when detached leaves were fed with water and rehydrated. The reason for this inhibition has still to be identified.     

Potassium nutrition of Cabernet Sauvignon grapevines (Vitis vinifera L.) as affected by shoot trimming

As potassium (K) requirement of grapevine (Vitis viniferaL.) berries is high and phloem translocation from mature leaves to developing organs is well established, it was posited that shoot trimming, a widely applied technique which alters the source-sink balance and the mature-to-immature foliage ratio of a canopy, may influence K deficiency. Six-year-old Cabernet Sauvignon grapevines were grown in 0.045 m³ pots (one plant per pot) filled with a soil sampled from a vineyard previously displaying K deficiency symptoms. Two levels of K supply (K₀, no K added; K_1, 25 g K per pot added in five splits from bloom to post veraison) were tested on vines that for each level were left (a) untrimmed and trimmed at ten main leaves with (b) or without (c) maintenance of lateral shoots in a split-plot design. Potassium concentration of leaf blades, berries and canes, vegetative growth and leaf gas exchange were recorded throughout the season; yield, grape quality and must characteristics were determined at fruit maturity. While adding potassium to the soil resulted in higher K concentration in blades of both main and lateral shoots and berries at harvest, trimming with removal of lateral shoots resulted in lower blade K concentration of the main leaves at harvest and more severe K deficiency symptoms regardless of K soil availability. Berry K concentration and the fraction of whole-plant K partitioned to clusters were not significantly affected by trimming. Gas-exchange, vegetative growth, yield and grape quality were not affected by the seasonal K fertilization, whereas the latter was impaired when trimming with excision of lateral shoots was applied. The results indicate that if shoot trimming is not followed by an adequate regrowth of secondary shoots an excessive depletion of potassium from the retained old basal leaves occurs during fruit maturity and increases the risk of leaf K deficiency, particularly in the K₀ treatment.     

Sap flow in wheat under free-air CO2 enrichment

The effects of elevated carbon dioxide (CO₂) concentration on plant water use are best evaluated on plants grown under field conditions and with measurement techniques that do not disturb the natural function of the plant. Heat balance sap flow gauges were used on individual main stems of wheat (Triticum aestivum L. cv Yecora rojo) grown under normal ambient conditions (control) and in a free-air CO₂ enrichment (FACE) system in Arizona with either high (control + high H₂O = CW; FACE + high H₂O = FW) or low (control + low H₂O = CD; FACE + low H₂O = FD) irrigation regimens. Over a 30d period (stem elongation to anthesis), combinations of treatments were monitored with,10–40 gauges per treatment. The effects of increased CO₂ on tiller water use were inconsistent in both the diurnal patterns of sap flow and the statistical analyses of daily sap flow (F_tot). Initial results suggested that the reductions in F_tot, from CO₂ enrichment were small (,0–10%) in relation to the H₂O treatment effect (,20–30%). For a 3d period, F_tot of FW was,19–26% less than that of CW (P = 0.10). Examination of the different sources of variation in the study revealed that the location of gauges within the experimental plots influenced the variance of the sap flow measurements. This variation was probably related to positional variation in subsurface drip lines used to irrigate plots. A sampling design was proposed for use of sap flow gauges in FACE systems with subsurface irrigation that takes into account the main treatment effects of CO₂ enrichment and the other sources of variation identified in this study. Despite the small and often statistically non-significant differences in F_tot between the CW and FW treatments, cumulative water use of the FW treatment at the end of the first three test periods ranged from 7 to 23% lower than that of the CW treatment. Differences in sap flow between FW and CW compared well with treatment differences in evapotranspiration. The results of the study, based on the first reported sap flow measurements of wheat, suggest that irrigation requirements for wheat production, in the present climatic regimen of the south-western US, may be predicted to decrease slightly because of increasing atmospheric CO₂.     

Sap flow rates and sapwood density are critical factors in within- and between-tree variation in CO2 efflux from stems of mature Dacrydium cupressinum trees

Measurements of CO2 efflux from stems and branches, sap velocity, and respiratory activity of excised wood cores were conducted in Dacrydium cupressinum trees that differed in diameter, age, and canopy emergence. The objective of this study was to determine if consistent linkages exist among respiratory production of CO2 within stems, xylem transport of CO2, and the rate of CO2 diffusing from stem surfaces. Stem CO2 efflux was depressed during periods of sap flow compared with the efflux rate expected for a given stem temperature and was positively correlated with sapwood density. By contrast, no significant relationships were observed between CO2 efflux and the respiratory activity of wood tissues. Between 86 and 91% of woody tissue respiration diffused to the atmosphere over a 24-h period. However, at certain times of the day, xylem transport and internal storage of CO2 may account for up to 13-38% and 12-18%, respectively, of woody tissue respiration. These results demonstrate that differences in sap flow rates and xylem anatomy are critically important for explaining within- and between-tree variation in CO2 efflux from stems.     

Measurement of stem respiration of sycamore (Platanus occidentalis L.) trees involves internal and external fluxes of CO2 and possible transport of CO2 from roots

CO(2) released by respiring cells in tree stems can either diffuse to the atmosphere or dissolve in xylem sap. In this study, the internal and external fluxes of CO(2) released from respiring stems of five sycamore (Platanus occidentalis L.) trees were calculated. Mean rates of stem respiration were highest in mid-afternoon and lowest at night, and were positively correlated with air temperature. Over a 24 h period, on average 34% of the CO(2) released by respiring cells in the measured stem segment remained within the tree. CO(2) efflux to the atmosphere consisted of similar proportions of CO(2) derived from local respiring cells (55%) and CO(2) that had been transported in the xylem (45%), indicating that CO(2) efflux does not accurately estimate respiration. A portion of the efflux of transported CO(2) appeared to have originated in the root system. A modification of the method for calculating stem respiration based on internal and external fluxes of CO(2) was developed to separate efflux due to local respiration from efflux of transported CO(2).     

Anthocyanin production in selected cell lines of grape (Vitis vinifera L.)

Summary Anthocyanin production of two lines ofVitis vinifera cell cultures, i.e., 5.4 and 13.1, which were obtained from the same starting material after 20 and 37 mo. of clonal selection, respectively, was investigated. Cell suspension cultures of lines 5.4 and 13.1 maintained an anthocyanin content of 0.44 ± 0.15 and 1.02 ± 0.31 mg·g⁻¹ fresh weight during 50 and 32 weekly maintenance subcultures, respectively. Under anthocyanin-promoting culture conditions, both lines showed an enhancement of their anthocyanin level by approximately fourfold. While line 5.4 accumulated peonidin 3-glucoside and cyanidin 3-glucoside in decreasing order, line 13.1 accumulated primarily peonidin 3-p-coumaroylglucoside with lesser amounts of malvidin monoglucoside. Results show that while the anthocyanin content was improved during the course of repeated selections, the anthocyanin composition was modified markedly favoring the accumulation of more metabolically-advanced anthocyanins.     

Phenology of flowering and starch accumulation in grape (Vitis vinifera L.) cuttings and vines

BACKGROUND AND AIMS: A reliable protocol for flowering and fruiting in cuttings was developed with the aim of (a) studying inflorescence and flower development in grapevine cuttings and field plants, and (b) assisting haploid plant production. METHODS: Inflorescence and flower development was studied in 'Gewurztraminer' (GW) and 'Pinot Noir' (PN) grape vines and cuttings grown in a glasshouse, along with variations in starch in the flowers. As there is a strong relationship between flower development and starch, the starch content of reproductive structures was estimated. KEY RESULTS: Inflorescence and flower development were similar in the vines and cuttings with consistent differences between the two cultivars. Indeed, the ontogenesis of male and female organs is not synchronous in GW and PN, with both female and male meiosis occurring earlier in PN than in GW. Moreover, changes of starch reserves were similar in the two plant types. CONCLUSIONS: Cuttings have a similar reproductive physiology to vines, and can be used to study grape physiology and to develop haploid plants.     

Cellular expansion and gene expression in the developing grape (Vitis vinifera L.)

Summary. Expression profiles of genes involved in cell wall metabolism and water transport were compared with changes in grape (Vitis vinifera L.) berry growth, basic chemical composition, and the shape, size, and wall thickness of cells within tissues of the berry pericarp. Expression of cell wall-modifying and aquaporin genes in berry pericarp tissues generally followed a bimodal expression profile with high levels of expression coinciding with the two periods of rapid berry growth, stages I and III, and low levels of expression corresponding to the slow-growth period, stage II. Cellular expansion was observed throughout all tissues during stage I, and only mesocarp cellular expansion was observed during stage III. Expansion of only exocarp cells was evident during transition between stages II and III. Cell wall-modifying and aquaporin gene expression profiles followed similar trends in exocarp and mesocarp tissues throughout berry development, with the exception of the up-regulation of pectin methylesterase, pectate lyase, two aquaporin genes (AQ1 and AQ2), and two expansin genes (EXP3 and EXPL) during stage II, which was delayed in the exocarp tissue compared with mesocarp tissue. Exocarp endo-(1→3)-β-glucanase and expansin-like gene expression was concurrent with increases in epidermal and hypodermal cell wall thickness. These results indicate a potential role of the grape berry skin in modulating grape berry growth. Correspondence: P. Bowen, Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC V0H 1Z0, Canada     

QTLs for muscat flavor and monoterpenic odorant content in grapevine (Vitis vinifera L.)

Little is known about the genetic determinism of muscat flavor in grape, although this trait is of major importance for table grape breeding. We therefore performed a search for QTLs (Quantitative Trait Loci) of both muscat score and berry content in the three main free monoterpene alcohols potentially involved, linalool, nerol and geraniol, based on two years of measures. Parental and consensus framework genetic maps of the cross MTP2687-85 (Olivette × Ribol) × Muscat of Hamburg were built after genotyping the 174 offspring for 139 well-scattered SSR markers. The female, male and consensus framework maps spanned 935, 1365 and 1267 cM, respectively. For QTL detection, simple and composite interval mapping were performed, as well as non parametric Kruskal–Wallis tests. QTLs for muscat score were found on linkage groups (LGs) 1, 5 and 7. For the three ln-transformed monoterpene contents, QTLs with major effects (explaining 17–55 % of total phenotypic variance) were found to be colocated on LG 5, on the male and consensus maps in both years. One additional QTL was found for linalool on LG 2, on female and consensus maps, as well as other colocated ones for nerol and geraniol on LG 13, on male and consensus maps. These additional QTLs had lower effects (9–25%). The contribution of these results to the knowledge of muscat aroma genetic determinism is discussed, as well as their potential usefulness for marker assisted breeding of new aromatic grape varieties.     

Partitioning and mobilization of starch and N reserves in grapevine (Vitis vinifera L.)

We followed C and N reserves of grapevines grown in trenches under semi-controlled conditions over a 3-year period after planting. Temporal mobilization of stored C and N and subsequent distribution of reserve materials within the vines were described in parallel with 15N uptake, particularly during the third growing season. Storage C in the perennial tissues (roots, trunk, canes) was mainly made of starch, which accumulated in the ray parenchyma of the wood. In the permanent tissues, starch and total nitrogen contents were found to decrease early in the development (bleeding sap, budbreak) whereas, on a concentration basis, they decreased only after stage 7 (first leaf fully expanded). Starch started to accumulate again in the perennial tissues during flowering. The same observation was made with total nitrogen, although N levels were much lower than those of starch. The 15N study showed that N uptake by the roots started at budbreak and increased with vine development, becoming predominant over reserve mobilization only after the onset of flowering. Taken together, these results indicate that the spring growth period can be divided into three main phases: In the first (dormancy to budbreak), significant losses of C and N proceed mainly via root necrosis. In the second period (first leaf to the onset of bloom), a strong mobilization of starch (and, to a lower extent, of N) occurred for supporting vegetative and reproductive growth. At that point, most of the C and N reserves used on the spring flush were those of the roots, rather than those of the old wood (trunk, canes). In the third period (bloom and early berry development), the mobilization process became low and was relieved by N uptake (and CO2 assimilation) supplying nutrients to the sink structures.     

Relationships between plant and soil water status in vine (Vitis vinifera L.)

Soil water status and its effect on plant water status are commonly evaluated for water stress diagnosis in annual crops. We investigated the application of this method to vineyards, using the fraction of transpirable soil water (FTSW) to characterise the soil water deficit experienced by the plant. The stability of the relationship between FTSW and predawn leaf water potential (Ψp) was analysed over two years (2000–2001), in two contrasted soils in vineyards in south eastern France, both planted with the cultivar Syrah, but grafted on different rootstocks (SO4 and 140Ru). FTSW was determined from soil moisture measurements performed with a neutron probe down to 2.5 m, under the rows and between the rows (3 replicates in each case). Vertical and horizontal variations in soil water content were analysed and the upper and lower limits of total vine’s transpirable soil water (TTSW) were calculated for each soil. The lower limit was also compared with the value of soil moisture content determined at −1.5 MPa in the laboratory. FTSW could be calculated for the soil depth analysed, without distinguishing horizontal position (row or inter-row). The lower limit of TTSW for vine was higher than the soil water content at −1.5 MPa, except in the upper horizons (0–0.2 m) which are prone to soil evaporation. A single relationship between Ψp and FTSW was obtained for the two vineyards and for the two years of measurement. This relationship was similar to that established by Lebon et al. (2003) on Gewürztraminer/SO4 in a vineyard in northern France. FTSW can therefore be used as an indicator of the water deficit experienced in vineyards, provided that TTSW is correctly estimated.     

Hydraulic limitation not declining nitrogen availability causes the age‐related photosynthetic decline in loblolly pine (Pinus taeda L.)

Declining net primary production (NPP) with forest age is often attributed to a corresponding decline in gross primary production (GPP). We tested two hypotheses explaining the decline of GPP in ageing stands (14–115 years old) of Pinus taeda L.: (1) increasing N limitation limits photosynthetic capacity and thus decreases GPP with increasing age; and (2) hydraulic limitations increasingly induce stomatal closure, reducing GPP with increasing age. We tested these hypotheses using measurements of foliar nitrogen, photosynthesis, sap‐flow and dendroclimatological techniques. Hypothesis (1) was not supported; foliar N retranslocation did not increase and declines were not observed in foliar N, leaf area per tree or photosynthetic capacity. Hypothesis (2) was supported; declines were observed in light‐saturated photosynthesis, leaf‐ and canopy‐level stomatal conductance, concentration of CO₂ inside leaf air‐spaces (corroborated by an increase in wood δ¹³C) and specific leaf area (SLA), while stomatal limitation and the ratio of sapwood area (SA) to leaf area increased. The sensitivity of radial growth to inter‐annual variation in temperature and drought decreased with age, suggesting that tree water use becomes increasingly conservative with age. We conclude that hydraulic limitation increasingly limits the photosynthetic rates of ageing loblolly pine trees, possibly explaining the observed reduction of NPP.     

葡萄胚胎发育与败育过程中胚珠的多胺含量变化

花后40~60d期间,种子败育型无核葡萄胚珠的3种多胺含量明显低于有核葡萄,据此认为无核葡萄胚珠中多胺含量急剧下降和较低的多胺水平可能是导致葡萄胚胎败育的重要原因。(Spd Spm)/Put和Spm/PAs比值变化与葡萄胚胎发育密切相关,较低的比值不利于胚胎的正常分化。     

Dynamic changes in petiole specific conductivity in red maple (Acer rubrum L.), tulip tree (Liriodendron tulipifera L.) and northern fox grape (Vitis labrusca L.)

Diurnal variation in petiole specific hydraulic conductivity and simultaneous measurements of leaf water potential were recorded in red maple, tulip tree and fox grape. Petiole specific conductivity was determined from in situ measurements of water flow into the distal (leaf‐bearing) end of an attached petiole as a function of applied hydrostatic pressure and petiole dimensions. The hydraulic properties of the petiole dominated the measurements, indicating that this technique can be used for rapid estimates of petiole hydraulic conductivity. There was a significant decrease in petiole specific conductivity associated with increasingly more negative leaf water potentials in maple and tulip tree, but not in grape. Petiole specific conductivity increased during the afternoon while the plant was actively transpiring and the xylem sap was under tension. The recovery of petiole conductivity during the afternoon suggests that hydraulic conductivity reflects a dynamic balance between a loss of hydraulic conductivity with increasing water stress, and its restoration as tension within the xylem decreases. Three experimental manipulations were applied to red maple and tulip tree to examine the sensitivity of diurnal changes in petiole conductivity to various physiological perturbations. Both phloem girdling and application of HgCl₂ to the transpiration stream resulted in a marked decrease in the degree to which petiole specific conductivity recovered as xylem tension relaxed during the afternoon. Delivery of a surfactant to the xylem, however, did not significantly alter the relation between leaf water potential and petiole hydraulic conductivity.