ABSTRACT
We examined the role of aquaporins (AQPs) in regulating leaf hydraulic conductance (Kleaf) in Vitis vinifera L. (cv Chardonnay) by studying effects of AQP inhibitors, and AQP gene expression ...during water stress (WS) and recovery (REC). Kleaf was measured after 3 h of petiole perfusion with different solutions and to introduce inhibitors. The addition of 0.1 mm HgCl2 to 15 mm KCl reduced Kleaf compared with perfusion in 15 mM KNO3 or KCl, and these solutions were used for leaves from control, WS and REC plants. Perfusion for 3 h did not significantly alter stomatal conductance (gs) though expression of VvTIP1;1 was increased. WS decreased Kleaf by about 30% and was correlated with gs. The expression of VvTIP2;1 and VvPIP2;1 correlated with Kleaf, and VvTIP2;1 was highly correlated with gs. There was no association between the expression of particular AQPs during WS and REC and inhibition of Kleaf by HgCl2; however, HgCl2 treatment itself increased expression of VvPIP2;3 and decreased expression of VvPIP2;1. Inhibition by HgCl2 of Kleaf only at early stages of WS and then after REC suggested that apoplasmic pathways become more important during WS. This was confirmed using fluorescent dyes confined to apoplasm or preferentially accumulated in symplasm.
We examine the role of aquaporins in regulating leaf hydraulic conductance of Vitis vinifera L. (cv Chardonnay) by studying effects of aquaporin inhibitors, and aquaporin gene expression during water stress and recovery. Water stress decreased hydraulic conductance by about 30% and was correlated with stomatal conductance. The expression of two aquaporin genes correlated with hydraulic conductance, and expression of a TIP aquaporin was highly correlated with stomatal conductance. Apoplasmic pathways for water flow appeared to be more prominent during water stress.
Plant water use efficiency (WUE) is becoming a key issue in semiarid areas, where crop production relies on the use of large volumes of water. Improving WUE is necessary for securing environmental ...sustainability of food production in these areas. Given that climate change predictions include increases in temperature and drought in semiarid regions, improving crop WUE is mandatory for global food production. WUE is commonly measured at the leaf level, because portable equipment for measuring leaf gas exchange rates facilitates the simultaneous measurement of photosynthesis and transpiration. However, when those measurements are compared with daily integrals or whole-plant estimates of WUE, the two sometimes do not agree. Scaling up from single-leaf to whole-plant WUE was tested in grapevines in different experiments by comparison of daily integrals of instantaneous water use efficiency ratio between CO2 assimilation (AN) and transpiration (E); AN/E with midday AN/E measurements, showing a low correlation, being worse with increasing water stress. We sought to evaluate the importance of spatial and temporal variation in carbon and water balances at the leaf and plant levels. The leaf position (governing average light interception) in the canopy showed a marked effect on instantaneous and daily integrals of leaf WUE. Night transpiration and respiration rates were also evaluated, as well as respiration contributions to total carbon balance. Two main components were identified as filling the gap between leaf and whole plant WUE: the large effect of leaf position on daily carbon gain and water loss and the large flux of carbon losses by dark respiration. These results show that WUE evaluation among genotypes or treatments needs to be revised.
► The intention of the present review is to update the consensus knowledge on gm. ► Gaps in knowledge and research priorities are indicated for the near future. ► In particular, how has gm evolved ...among phylogenetically distant groups? ► Can gm be uncoupled from the water path regulation? ► Mechanistic models of gm incorpored in photosynthesis models are needed.
Mesophyll diffusion conductance to CO2 is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of gm, and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance.
Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted.
Background and Aim. The genetically determined characteristics of grapevine rootstocks are important factors that affect scion performance. This 3 years’ field study aimed to characterize the ...influence of four well-established 30-year-old rootstocks (110 Richter, 1103 Paulsen, 41B, and 161-49Couderc) on the Tempranillo cultivar in the semiarid wine growing region of D.O.Ca. Rioja, North-Eastern Spain. Methods and Results. Nutrient concentrations of mineral elements at flowering and veraison were determined in the vines, jointly with grapevine-water status, gas exchange, vine vigour, and chlorophyll content. Moreover, grapevine yield and grape quality were determined at harvest. The least vigorous rootstocks (41B, 161-49C) conferred drought adaptability traits by increasing water use efficiency (WUE) and decreasing whole-plant water conductance per unit leaf area (Kplant) compared to the more vigorous rootstocks (1103-P, 110-R). In contrast, the more vigorous rootstocks increased water transport capacity, which led to higher plant performance and nutrient uptake efficiency. At flowering, 1103-P and to a lesser extent, 110-R were most efficient at taking up nutrients, while 161-49C had the lowest concentrations for most nutrients. At veraison, 41B exhibited closer behaviour to 110-R than 161-49C, while 1103-P and 161-49C remained the most differentiated rootstocks, with higher and lower nutrient uptake, respectively. In addition, compared to the more vigorous rootstocks, the yield was up to 1.6 kg lower for the less vigorous rootstocks but the grape composition was improved. Notably, 161-49C led to higher total soluble solids, total acidity, and polyphenol content. Conclusions. Overall, grafting onto specific rootstocks represents a strategy to confer differential regulation of grapevine water-saving strategies, yield, berry quality, and nutrient uptake potential. Significance of the Study. This information may be useful for growers seeking to develop a site-specific selection of rootstocks for the grafted Tempranillo cv.
While the responses of photosynthesis to water stress have been widely studied, acclimation to sustained water stress and recovery after re-watering is poorly understood. In particular, the factors ...limiting photosynthesis under these conditions, and their possible interactions with other environmental conditions, are unknown. To assess these issues, changes of photosynthetic CO₂ assimilation (AN) and its underlying limitations were followed during prolonged water stress and subsequent re-watering in tobacco (Nicotiana sylvestris) plants growing under three different climatic conditions: outdoors in summer, outdoors in spring, and indoors in a growth chamber. In particular, the regulation of stomatal conductance (gs), mesophyll conductance to CO₂ (gm), leaf photochemistry (chlorophyll fluorescence), and biochemistry (Vc,max) were assessed. Leaf gas exchange and chlorophyll fluorescence data revealed that water stress induced a similar degree of stomatal closure and decreased AN under all three conditions, while Vc,max was unaffected. However, the behaviour of gm differed depending on the climatic conditions. In outdoor plants, gm strongly declined with water stress, but it recovered rapidly (1-2 d) after re-watering in spring while it remained low many days after re-watering in summer. In indoor plants, gm initially declined with water stress, but then recovered to control values during the acclimation period. These differences were reflected in different velocities of recovery of AN after re-watering, being the slowest in outdoor summer plants and the fastest in indoor plants. It is suggested that these differences among the experiments are related to the prevailing climatic conditions, i.e. to the fact that stress factors other than water stress have been superimposed (e.g. excessive light and elevated temperature). In conclusion, besides gs, gm contributes greatly to the limitation of photosynthesis during water stress and during recovery from water stress, but its role is strongly dependent on the impact of additional environmental factors.
ABSTRACT
Leaf water gets isotopically enriched through transpiration, and diffusion of enriched water through the leaf depends on transpiration flow and the effective path length (L). The aim of this ...work was to relate L with physiological variables likely to respond to similar processes. We studied the response to drought and vein severing of leaf lamina hydraulic conductance (Klamina), mesophyll conductance for CO2 (gm) and leaf water isotope enrichment in Vitis vinifera L cv. Grenache. We hypothesized that restrictions in water pathways would reduce Klamina and increase L. As a secondary hypothesis, we proposed that, given the common pathways for water and CO2 involved, a similar response should be found in gm. Our results showed that L was strongly related to mesophyll variables, such as Klamina or gm across experimental drought and vein‐cutting treatments, showing stronger relationships than with variables included as input parameters for the models, such as transpiration. Our findings were further supported by a literature survey showing a close link between L and leaf hydraulic conductance (Kleaf = 31.5 × L−0.43, r2 = 0.60, n = 24). The strong correlation found between L, Klamina and gm supports the idea that water and CO2 share an important part of their diffusion pathways through the mesophyll.
Effective pathlength (L) is a parameter of leaf water enrichment model, theoretically related to water pathways from veins to evaporative sites. This work relates for the first time L with measurable mesophyll variables, such as leaf lamina hydraulic conductance (Klam) or mesophyll conductance for CO2 (gm). The study combines experimental drought and vein cutting treatments in Grenache grapevine with a meta‐analysis on published data of L and hydraulic conductance. The strong correlation found between L, Klamina and gm supports the idea that water and CO2 share an important part of their diffusion pathways through the mesophyll.
The European grapevine moth (EGVM) Lobesia botrana (Lepidoptera: Tortricidae) is a relevant pest in the Palearctic region vineyards and is present in the Americas. Their management using biological ...control agents and environmentally friendly biotechnical tools would reduce intensive pesticide use. The entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are well-known virulent agents against arthropod pests thanks to symbiotic bacteria in the genera Xenorhabdus and Photorhabdus (respectively) that produce natural products with insecticidal potential. Novel technological advances allow field applications of EPNs and those bioactive compounds as powerful bio-tools against aerial insect pests. This study aimed to determine the viability of four EPN species (Steinernema feltiae, S. carpocapsae, S. riojaense, and Heterorhabditis bacteriophora) as biological control agents against EGVM larval instars (L1, L3, and L5) and pupae. Additionally, the bioactive compounds from their four symbiotic bacteria (Xenorhabdus bovienii, X. nematophila, X. kozodoii, and Photorhabdus laumondii subsp. laumondii, respectively) were tested as unfiltered ferment (UF) and cell-free supernatant (CFS) against the EGVM larval instars L1 and L3. All of the EPN species showed the capability of killing EGVM during the larval and pupal stages, particularly S. carpocapsae (mortalities of ~50% for L1 and >75% for L3 and L5 in only two days), followed by efficacy by S. feltiae. Similarly, the bacterial bioactive compounds produced higher larval mortality at three days against L1 (>90%) than L3 (~50%), making the application of UF more virulent than the application of CFS. Our findings indicate that both steinernematid species and their symbiotic bacterial bioactive compounds could be considered for a novel agro-technological approach to control L. botrana in vineyards. Further research into co-formulation with adjuvants is required to expand their viability when implemented for aboveground grapevine application.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Water scarcity is a main challenge in vineyards sustainability in most of the grapevine areas now and even more in near future due to climatic change perspectives. In consequence, water use ...efficiency (WUE) measurements are of the highest interest to improve the sustainability of this crop. The vast majority of WUE measurements relays on measurements of leaf carbon and water fluxes at leaf-level. However, less data are available at the whole-plant level, and for the moment those data are not totally coincident with conclusions reached at leaf scale. In this study, we used whole-plant chambers able to enclose an entire plant of 12 years old to measure at the same time water and carbon fluxes under realistic field grown conditions. The main objectives were to identify the technical issues interfering the whole-plant measurements and track the environmental and other abiotic factors that can affect water and carbon balance, i.e., WUE at the whole-plant scale. To achieve those objectives, we measured whole-plant water and carbon fluxes in grapevine exposed to two different water regimes at three phenological stages pea size (July), ripening (August), and harvest (September). In September, measurements were repeated under high CO
to also check its effect at the whole-plant scale. The results indicate that water and carbon fluxes are well coordinated under both water availability treatments. Under drought conditions, both fluxes were drastically reduced, but surprisingly the estimated WUE resulted not improved but decreased, contrarily to what is shown at the leaf scale. The phenology (September) also strongly decreased both water and carbon fluxes when compared to measurements in July. We hypostatized that harvest load respiration rates could have an important weight on the whole-plant net carbon exchange (NCE). Finally, high CO
measurements, after correction for leaks, indicated an increase of whole-plant NCE as well as increased whole-plant WUE, as expected. Several technical issues were identified, like 1/instability of CO
during the night period that prevent robust estimation of whole-plant respiration and 2/condensation during last night and sun-rise hours which may affect the estimation of daily plant transpiration.
Water limitation is one of the major threats affecting grapevine production. Thus, improving water‐use efficiency (WUE) is crucial for a sustainable viticulture industry in Mediterranean regions. ...Under field conditions, water stress (WS) is often combined with viral infections as those are present in major grape‐growing areas worldwide. Grapevine leafroll‐associated virus 3 (GLRaV‐3) is one of the most important viruses affecting grapevines. Indeed, the optimization of water use in a real context of virus infection is an important topic that needs to be understood. In this work, we have focused our attention on determining the interaction of biotic and abiotic stresses on WUE and hydraulic conductance (Kh) parameters in two white grapevine cultivars (Malvasia de Banyalbufar and Giró Ros). Under well‐watered (WW) conditions, virus infection provokes a strong reduction (P < 0.001) in Kpetiole in both cultivars; however, Kleaf was only reduced in Malvasia de Banyalbufar. Moreover, the presence of virus also reduced whole‐plant hydraulic conductance (Khplant) in 2013 and 2014 for Malvasia de Banyalbufar and in 2014 for Giró Ros. Thus, the effect of virus infection on water flow might explain the imposed stomatal limitation. Under WS conditions, the virus effect on Kplant was negligible, because of the bigger effect of WS than virus infection. Whole‐plant WUE (WUEWP) was not affected by the presence of virus neither under WW nor under WS conditions, indicating that plants may adjust their physiology to counteract the virus infection by maintaining a tight stomatal control and by sustaining a balanced carbon change.
The meadow spittlebug
(Hemiptera: Aphrophoridae) is the primary vector of
(Proteobacteria: Xanthomonadaceae) in Europe, a pest-disease complex of economically relevant crops such as olives, almonds, ...and grapevine, managed mainly through the use of broad-spectrum pesticides. Providing environmentally sound alternatives to reduce the reliance on chemical control is a primary challenge in the control of
and, hence, in the protection of crops against the expansion of its associated bacterial pathogen. Entomopathogenic nematodes (EPNs) are well-known biocontrol agents of soil-dwelling arthropods. Recent technological advances in field applications, including improvements in obtaining cell-free supernatant from their symbiotic bacteria, allow their successful implementation against aerial pests. Thus, this study aimed to evaluate, for the first time, the efficacy of EPN applications against nymphal instars of
We tested four EPN species and the cell-free supernatant of their corresponding symbiotic bacteria:
-
,
-
,
-
, and
-
subsp.
. First, we showed that 24 and 72 h exposure to the foam produced by
nymphs did not affect
virulence. The direct application of steinernematid EPNs provided promising results, reaching 90, 78, and 53% nymphal mortality rates after five days of exposure for
,
, and
, respectively. Conversely, the application of the cell-free supernatant from
resulted in nymphal mortalities of 64%, significantly higher than observed for
species after five days of exposure. Overall, we demonstrated the great potential of the application of specific EPNs and cell-free supernatant of their symbiont bacteria against
, introducing new opportunities to develop them as biopesticides for integrated management practices or organic vineyard production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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