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

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

Erratum

Adaptation of leaves of Vitis vinifera L to seasonal drought as affected by leaf ageVitis 36 (1), 1114 (1997

Midday measurements of leaf water potential and stomatal conductance are highly correlated with daily water use of Thompson Seedless grapevines

A study was conducted to determine the relationship between midday measurements of vine water status and daily water use of grapevines measured with a weighing lysimeter. Water applications to the vines were terminated on August 24th for 9 days and again on September 14th for 22 days. Daily water use of the vines in the lysimeter (ETLYS) was approximately 40 L vine−1 (5.3 mm) prior to turning the pump off, and it decreased to 22.3 L vine−1 by September 2nd. Pre-dawn leaf water potential (ΨPD) and midday Ψl on August 24th were −0.075 and −0.76 MPa, respectively, with midday Ψl decreasing to −1.28 MPa on September 2nd. Leaf g s decreased from ~500 to ~200 mmol m−2 s−1 during the two dry-down periods. Midday measurements of g s and Ψl were significantly correlated with one another (r = 0.96) and both with ETLYS/ETo (r = ~0.9). The decreases in Ψl, g s, and ETLYS/ETo in this study were also a linear function of the decrease in volumetric soil water content. The results indicate that even modest water stress can greatly reduce grapevine water use and that short-term measures of vine water status taken at midday are a reflection of daily grapevine water us

Influence of soil water content and atmospheric conditions on leaf water potential in cv. "Touriga Nacional" deep-rooted vineyards

Abstract In this study, the influence of soil and atmosphere conditions on noon and basal leaf water potential of vines ‘‘Touriga Nacional’’ in the Da˜o region submitted to different irrigation treatments is analysed. Both indicators showed to be dependent on environmental conditions at the time of measurement. Leaf water potential at noon of fully watered plants was linearly related with atmospheric conditions, with values registered when vapour pressure deficit (VPD) was higher than approximately 3 kPa being no different from the values registered in stressed plants. Therefore, this indicator cannot be reliably used to distinguish different plant water stress levels when atmospheric conditions induce high evaporative demands. The basal leaf water potential (wb) was also influenced by VPD at the time of measurement for all soil water conditions. In well irrigated plants, it was even possible to establish a baseline that can therefore be used to identify nonwater stressed conditions (wb (MPa) = -0.062–0.0972 VPD (kPa), r2 = 0.78). A good correlation was found between soil humidity and wb. However, more than the average value of the whole thickness of soil monitored, the wb values were dependent on the distribution of soil humidity, with the plants responding to the presence of wet layers

Ubiquitous LEA29Y Expression Blocks T Cell Co-Stimulation but Permits Sexual Reproduction in Genetically Modified Pigs

We have successfully established and characterized a genetically modified pig line with ubiquitous expression of LEA29Y, a human CTLA4-Ig derivate. LEA29Y binds human B7.1/CD80 and B7.2/CD86 with high affinity and is thus a potent inhibitor of T cell co-stimulation via this pathway. We have characterized the expression pattern and the biological function of the transgene as well as its impact on the porcine immune system and have evaluated the potential of these transgenic pigs to propagate via assisted breeding methods. The analysis of LEA29Y expression in serum and multiple organs of CAG-LEA transgenic pigs revealed that these animals produce a biologically active transgenic product at a considerable level. They present with an immune system affected by transgene expression, but can be maintained until sexual maturity and propagated by assisted reproduction techniques. Based on previous experience with pancreatic islets expressing LEA29Y, tissues from CAG-LEA29Y transgenic pigs should be protected against rejection by human T cells. Furthermore, their immune-compromised phenotype makes CAG-LEA29Y transgenic pigs an interesting large animal model for testing human cell therapies and will provide an important tool for further clarifying the LEA29Y mode of action

Water relation parameters in Vitis vinifera L in drought period. Effects of leaf age

The aim of this study was to evaluate the influence of leaf age on physiological mechanims adopted by grape vines (Vitis vinifera L) in order to sustain a favourable growth and production under drought conditions. The relationships between the water, turgor, osmotic potentials and leaf water content were studied during leaf ontogeny using both the pressure/volume and the psychometric technique. The symplasmic water fraction of the total water content decreased with leaf age. The capability for osmoregulation was almost the same in immature and mature leaves but decreased in old leaves. The calculated volumetric modulus of elasticity increased rapidly with leaf maturity and seems to be the dominant strategy for adaptation to drought conditions.Relations hydriques chez Vitis vinifera L soumise à la sécheresse. Effet de l'âge des feuilles. Le but de cette étude est d'évaluer l'influence de l'âge des feuilles sur les mécanismes physiologiques manifestés par la vigne (Vitis vinifera L) afin de maintenir une bonne production en condition de sécheresse. Les relations hydriques dans les feuilles ont été étudiées au cours de leur ontogenèse par l'établissement de courbes pression-volume et l'utilisation de la méthode psychométrique. L'eau symplasmique comme fonction du volume total de l'eau tissulaire diminue en fonction de l'âge des feuilles. La capacité d'osmorégulation paraît avoir les mêmes valeurs chez les feuilles adultes que chez les feuilles jeunes mais elle est fortement diminuée chez les feuilles âgées. Le module d'élasticité volumique calculé augmente rapidement avec l'âge et il semble être le mécanisme prépondérant de l'adaptation à la sécheresse chez la vigne