Osmoregulation in water stressed roots: Responses of leaf conductance and photosynthesis

Kober 5 BB vines were subjected to either moderate and slow soil dehydration or to repeated, severe and rapid stress and irrigation cycles. Moderate soil dehydration to 50 % of the soil water capacity led to a small but significant decrease of the osmotic potential at RWC = 100 %, i.e. to osmoregulation in root tips, but not in other parts of the roots. Osmoregulation was associated with the maintenance of a high water status in the root tips and high rates of leaf gas exchange. In a second experiment three severe and rapid drying cycles led to a decrease of the osmotic potential at RWC = 100 % in root tips as well as in unsuberised and suberised roots, the maximum rate being 2.3 bar. In this experiment osmoregulation in roots contributed to a partial increase of the root water status. The observation that, despite a low soil moisture content, leaf conductance and rate of photosynthesis had slightly recovered is discussed

Grapevine shoot growth and stomatal conductance are reduced when part of the root system is dried

Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on shoot growth and stomatal conductance of grape cultivars Chardonnay and Shiraz (syn. Syrah). When part of the root system was allowed to dry while the other part was well-watered, shoot growth was significantly reduced. Changes in both shoot growth and stomatal conductance in response to half-drying took place in the absence of any change in shoot water status suggesting the involvement of a non-hydraulic signal in mediating this response. Recovery of both shoot growth rate and stomatal conductance appeared to start before rewatering of the dried half of the root system, and coincided with the time when there was no further decrease of soil water content in the dried container. This appears to be first report of a significant decrease in shoot growth in response to partial drying of the root system of grapevines

Primary bud-axis necrosis of grapevines. I. Natural incidence and correlation with vigour

The incidence of primary bud-axis necrosis (PBN) was studied from 1980 to 1985 in Australian vineyards of varying vigour. Fifteen cultivars of Vitis vinifera L. were initially examined for the presence of PBN and, because Shiraz (syn. Syrah) proved to have the highest incidence, subsequent work emphasized this cultivar. Compound buds at nodes 2 to 9 from the base of the shoot (node 9 being the most distal node) were scored for the presence of PBN. PBN was found to be a significant cause of unfruitfulness in the Australian vineyards examined. Incidence was higher in seeded compared with seedless cultivars. Shiraz had the highest incidence but not as great as for other cultivars reported in Israel, Japan, Chile and USA. PBN incidence was highest in the basal nodes of thick shoots, especially if the node bore a lateral shoot. Buds with PBN produced more shoots but fewer bunches. Thinning of shoots ten days before and after flowering increased both shoot vigour and PBN incidence. This association was attributed to the greater vigour per se and not to any change in canopy light environment. PBN-caused loss of primary shoots is concluded to be a major cause of unfruitfulness in basal nodes of grapevine

Partial drying of the rootzone of grape. I. Transient changes in shoot growth and gas exchange

Split-root  plants, where  the  root  system was  divided between  two containers, were used  to  study  the effect  of  partial  drying  of  the  root  system  on  shoot growth and gas exchange of Shiraz  (syn. Syrah)  (Vitis vinifera), Kober 5 BB  (Vitis berlandieri x Vitis  riparia) and 110 Richter (Vitis berlandieri x Vitis rupestris). The initial decrease  in both shoot growth rate and gas exchange  in  response  to half-drying  coincided with  the decrease  in  soil water content of  the dried half of  the root  system. Recovery  of  shoot  function  of half-dried grapevines  occurred without  rewatering  of  the dried half  of  the  root  system,  and  commenced when  there was no  further decrease  in  soil water  content. There was no effect of half-drying on  leaf water potential at the  times  of  greatest  inhibition  of  shoot  growth  rate and stomatal conductance relative to control; this suggests  the  involvement of a non-hydraulic  signal originating  from  the  roots  in drying  soil. Changes  in  stomatal  conductance  in  response  to  half-drying were strongly  correlated with  shoot  growth  rate

Partial drying of the rootzone of grape. II. Changes in the pattern of root development

Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on gas exchange and root growth of 110 Richter (Vitis berlandieri x Vitis rupestris). The initial decrease in gas exchange in response to half-drying coincided with the decrease in soil water content of the dried half of the root system. Recovery of gas exchange of half-dried grapevines occurred without any further change in soil water content of the dried half of the root system, and coincided with the point at which there was no further decrease in soil water content. For half-dried plants, there was a relative increase in root development in moist soil layers, both in the wet container as a whole or in the lower part of the dry container. Recovery of gas exchange of half-dried plants occurred at the time when there were no more roots dried in the dry container. We propose that, for half-dried plants, the part of the root system in dry soil can survive because water moves from wet roots to dry roots

Effect of rootstock on nutrition, pollination and fertilisation in 'Shiraz' (Vitis vinifera L.)

Rootstocks have previously been shown to alter reproductive performance in grapevines. The concentration of nutrients associated with pollination and fertilisation in grapevines such as boron, calcium, zinc and molybdenum were determined in petiole and pollen tissue from vines from a 'Shiraz' (Vitis vinifera L.) rootstock trial at flowering. 'Shiraz' on own roots had a higher calcium concentration in the petioles across the three seasons than the rootstock treatments. This coincided with higher seeded berry number, total number of berries per bunch and berry weight compared to rootstock treatments. '1103 Paulsen' had a significantly higher amount of boron and a lower number of seedless berries and a lower millerandage index (MI). Zinc deficiency was observed for '110 Richter' and '140 Ruggeri' across the three seasons and when zinc was found to be deficient, coulure index (CI) was increased. In the third and final year of the analysis pollen nutrition was incorporated into the analysis. Deficiency of molybdenum in both pollen and petiole analysis resulted in reduced berry weight due to stenospermocarpy or seed shrivel. Rootstocks with the highest number of pollen grains on the stigma also had the highest number of ovules fertilised. Calcium, zinc, boron and molybdenum are nutrients essential for pollination and fertilisation in grapevines and rootstocks were found to affect the sequestration of nutrients which affected reproductive performance.

Revealing Correlation of Valence State with Nanoporous Structure in Cobalt Catalyst Nanoparticles by in Situ Environmental TEM

Simultaneously probing the electronic structure and morphology of materials at the nanometer or atomic scale while a chemical reaction proceeds is significant for understanding the underlying reaction mechanisms and optimizing a materials design. This is especially important in the study of nanoparticle catalysts, yet such experiments have rarely been achieved. Utilizing an environmental transmission electron microscope (ETEM) equipped with a differentially pumped gas cell, we are able to conduct nanoscopic imaging and electron energy loss spectroscopy (EELS) in situ for cobalt catalysts under reaction conditions. Analysis revealed quantitative correlation of the cobalt valence states to the particles' nanoporous structures. The in situ experiments were performed on nanoporous cobalt particles coated with silica while a 15 mTorr hydrogen environment was maintained at various temperatures (300-600\degreeC). When the nanoporous particles were reduced, the valence state changed from cobalt oxide to metallic cobalt and concurrent structural coarsening was observed. In situ mapping of the valence state and the corresponding nanoporous structures allows quantitatively analysis necessary for understanding and improving the mass activity and lifetime of cobalt-based catalysts, i.e., for Fischer-Tropsch synthesis that converts carbon monoxide and hydrogen into fuels, and uncovering the catalyst optimization mechanisms.Comment: ACS Nano, accepte

Ultrabithorax confers spatial identity in a context-specific manner in the Drosophila postembryonic ventral nervous system.

BACKGROUND: In holometabolous insects such as Drosophila melanogaster, neuroblasts produce an initial population of diverse neurons during embryogenesis and a much larger set of adult-specific neurons during larval life. In the ventral CNS, many of these secondary neuronal lineages differ significantly from one body segment to another, suggesting a role for anteroposterior patterning genes. RESULTS: Here we systematically characterize the expression pattern and function of the Hox gene Ultrabithorax (Ubx) in all 25 postembryonic lineages. We find that Ubx is expressed in a segment-, lineage-, and hemilineage-specific manner in the thoracic and anterior abdominal segments. When Ubx is removed from neuroblasts via mitotic recombination, neurons in these segments exhibit the morphologies and survival patterns of their anterior thoracic counterparts. Conversely, when Ubx is ectopically expressed in anterior thoracic segments, neurons exhibit complementary posterior transformation phenotypes. CONCLUSION: Our findings demonstrate that Ubx plays a critical role in conferring segment-appropriate morphology and survival on individual neurons in the adult-specific ventral CNS. Moreover, while always conferring spatial identity in some sense, Ubx has been co-opted during evolution for distinct and even opposite functions in different neuronal hemilineages