scholarly journals Effect of Long-Term vs. Short-Term Ambient Ozone Exposure on Radial Stem Growth, Sap Flux and Xylem Morphology of O3-Sensitive Poplar Trees

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 396 ◽  
Author(s):  
Alessio Giovannelli ◽  
Maria Laura Traversi ◽  
Monica Anichini ◽  
Yasutomo Hoshika ◽  
Silvano Fares ◽  
...  
Keyword(s):  
Water Use ◽  
Sap Flow ◽  
Stem Growth ◽  
Ozone Exposure ◽  
Compensatory Mechanisms ◽  
Planted Forests ◽  
Evaporative Demand ◽  
Huber Value ◽  
Stem Water

High ozone (O3) pollution impairs the carbon and water balance of trees, which is of special interest in planted forests. However, the effect of long-term O3 exposure on tree growth and water use, little remains known. In this study, we analysed the relationships of intra-annual stem growth pattern, seasonal sap flow dynamics and xylem morphology to assess the effect of long term O3 exposure of mature O3-sensitive hybrid poplars (‘Oxford’ clone). Rooted cuttings were planted in autumn 2007 and drip irrigated with 2 liters of water as ambient O3 treatment, or 450 ppm ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N0-phenylurea, abbreviated as EDU) solution as O3 protection treatment over all growing seasons. During 2013, point dendrometers and heat pulses were installed to monitor radial growth, stem water relations and sap flow. Ambient O3 did not affect growth rates, even if the seasonal culmination point was 20 days earlier on average than that recorded in the O3 protected trees. Under ambient O3, trees showed reduced seasonal sap flow, however, the lower water use was due to a decrease of Huber value (decrease of leaf area for sapwood unit) rather than to a change in xylem morphology or due to a direct effect of sluggish stomatal responses on transpiration. Under high evaporative demand and ambient O3 concentrations, trees showed a high use of internal stem water resources modulated by stomatal sluggishness, thus predisposing them to be more sensitive water deficit during summer. The results of this study help untangle the compensatory mechanisms involved in the acclimation processes of forest species to long-term O3 exposure in a context of global change.

scholarly journals Coordination of leaf area, sapwood area and canopy conductance leads to species convergence of tree water use in a remnant evergreen woodland

2008 ◽  
Vol 56 (2) ◽  
pp. 97 ◽  
Author(s):  
Melanie Zeppel ◽  
Derek Eamus
Keyword(s):  
Leaf Area ◽  
Water Use ◽  
Canopy Conductance ◽  
Evaporative Demand ◽  
Sapwood Area ◽  
Huber Value ◽  
Tree Water Use ◽  
Decoupling Coefficient ◽  
The Relationship ◽  
Daily Total

This paper compares rates of tree water use, Huber value, canopy conductance and canopy decoupling of two disparate, co-occurring tree species, in a stand of remnant native vegetation in temperate Australia in order to compare their relative behaviour seasonally and during and after a drought. The study site was an open woodland dominated by Eucalyptus crebra F.Muell. (a broad-leaved species) and Callitris glaucophylla J.Thompson & L.A.S. Johnson (a needle-leaved tree species). Tree water use was measured with sapflow sensors and leaf area and sapwood area were measured destructively on felled trees. The Huber value was calculated as the ratio of sapwood area to leaf area. Diameter at breast height (DBH) of the stem was used as a measure of tree size. Canopy conductance was calculated with an inversion of the Penman–Monteith equation, whereas canopy decoupling) was calculated as described by Lu et al. (2003). The relationship between DBH and daily total water use varied during the four measurement periods, with largest rates of water use observed in summer 2003–2004, following a large rainfall event and the smallest maximum water use observed in winter 2003 when monthly rainfall was much less than the long-term mean for those months. Despite differences in the relationship between sapwood area and DBH for the two species, the relationship between daily total water use and DBH did not differ between species at any time. The same rates of water use for the two species across sampling periods arose through different mechanisms; the eucalypt underwent significant changes in leaf area whereas the Callitris displayed large changes in canopy conductance, such that tree water use remained the same for both species during the 2-year period. Canopy conductance and the decoupling coefficient were both significantly larger in winter than summer in both years. The generally low decoupling coefficient (0.05–0.34) reflects the low leaf area index of the site. When evaporative demand was small (winter), the degree of stomatal control was small and the decoupling coefficient was large. There was no relationship between tree size and either canopy conductance or the decoupling coefficient. Transpiration rates generally showed little variation between seasons and between species because of the balance between changes in leaf area, canopy conductance and evaporative demand. The occurrence of a significant drought did not appear to prevent these coordinated changes from occurring, with the result that convergence in water use was observed for these two disparate species.

Sap velocity as an indicator of diurnal and long-term hydraulic resistance changes in mature ‘Walker’ hybrid poplar treesThis article is one of a selection of papers published in the Special Issue on Poplar Research in Canada.

2007 ◽  
Vol 85 (11) ◽  
pp. 1033-1041 ◽  
Author(s):  
J. Kort ◽  
T.J. Blake
Keyword(s):  
Water Potential ◽  
Hydraulic Resistance ◽  
Water Use ◽  
Sap Flow ◽  
Hybrid Poplar ◽  
Thermal Dissipation ◽  
Use Patterns ◽  
Poplar Trees ◽  
Water Use Patterns

Hydraulic resistance directly limits sap flow in trees so that understanding water-use patterns in poplar trees requires knowledge about diurnal and long-term changes in resistances in the soil–plant–atmosphere continuum. Granier thermal dissipation probes were used for continuous measurements of sap velocity (V) changes over time and whole-tree water-use patterns in the main stems of ‘Walker’ hybrid poplar trees. When atmospheric demand was low, V depended only on solar radiation (Rg) and vapour pressure difference (VPD). However, on warm, sunny days, midday V decreased, despite a constant leaf water potential (Ψl) of –1.5 MPa. Because bulk soil water potential (Ψs) did not change significantly, the constant Ψl implied that the water potential difference (ΔΨ) remained diurnally constant. Although stomatal control would explain changes in V when VPD was low, an increase in hydraulic resistance was required to explain the decrease in V when VPD was high. Xylem cavitation was ruled out as a cause because the apparent increase in resistance reversed in late afternoon, while VPD was still high. Mid-August irrigation immediately increased daily V, which was attributed to a change in ΔΨ because of less negative Ψs. A gradual increase in sap flow over two weeks following irrigation implied a decrease in plant hydraulic resistance, most likely attributable to new root growth. It was concluded that hydraulic resistance changes, both diurnal and in the longer term, occurred primarily at the rhizosphere or root level.

Xylem sap flow, growth and flower production of cultivated Geraldton wax with different vigour under semi-arid conditions

1995 ◽  
Vol 46 (3) ◽  
pp. 581
Author(s):  
K Akilan ◽  
JA Considine ◽  
JK Marshall
Keyword(s):  
Water Use ◽  
Sap Flow ◽  
Xylem Sap ◽  
Root Systems ◽  
Stem Length ◽  
Growth Responses ◽  
Evaporative Demand ◽  
Flower Production ◽  
Arid Conditions ◽  
Semi Arid

Diurnal and seasonal water use and the effects of different levels of irrigation on growth and flower production were studied using commercially cultivated Geraldton wax (Chamelaucium uncinatum Schauer cv. Purple Pride) under semi-arid conditions. Water use and growth responses to increased irrigation differed widely with vigour. Vigorous plants had extensive root systems and used more water than less vigorous plants whether irrigated or unirrigated and responded to increased irrigation by producing more shoots, secondary stems and flowers. In vigorous plants, marketable stem length and flower number were increased from 63 to 89 cm and 61 to 226 when irrigation was increased from 25 to 75% of pan replacement respectively. Less vigorous plants had distorted root systems (i.e. curling and circling) and showed no significant growth response to increased irrigation. Increase of stem length to a desirable length of 90 cm in less vigorous plants, which are wide-spread in commercial plantings, was unlikely. The results highlight the significance of good propagation and establishment techniques to aid vigorous growth. The sap flow study shows that Geraldton wax is a high water using species. A single plant can use in excess of 20 L per day under high evaporative demand when root growth is not limiting.

scholarly journals Overexpression of MdATG8i improves water use efficiency in transgenic apple by modulating photosynthesis, osmotic balance, and autophagic activity under moderate water deficit

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xin Jia ◽  
Ke Mao ◽  
Ping Wang ◽  
Yu Wang ◽  
Xumei Jia ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Deficit ◽  
Water Use ◽  
Photosynthetic Capacity ◽  
Critical Role ◽  
Drought Conditions ◽  
Moderate Drought ◽  
Use Efficiency ◽  
Autophagic Activity

AbstractWater deficit is one of the major limiting factors for apple (Malus domestica) production on the Loess Plateau, a major apple cultivation area in China. The identification of genes related to the regulation of water use efficiency (WUE) is a crucial aspect of crop breeding programs. As a conserved degradation and recycling mechanism in eukaryotes, autophagy has been reported to participate in various stress responses. However, the relationship between autophagy and WUE regulation has not been explored. We have shown that a crucial autophagy protein in apple, MdATG8i, plays a role in improving salt tolerance. Here, we explored its biological function in response to long-term moderate drought stress. The results showed that MdATG8i-overexpressing (MdATG8i-OE) apple plants exhibited higher WUE than wild-type (WT) plants under long-term moderate drought conditions. Plant WUE can be increased by improving photosynthetic efficiency. Osmoregulation plays a critical role in plant stress resistance and adaptation. Under long-term drought conditions, the photosynthetic capacity and accumulation of sugar and amino acids were higher in MdATG8i-OE plants than in WT plants. The increased photosynthetic capacity in the OE plants could be attributed to their ability to maintain optimal stomatal aperture, organized chloroplasts, and strong antioxidant activity. MdATG8i overexpression also promoted autophagic activity, which was likely related to the changes described above. In summary, our results demonstrate that MdATG8i-OE apple lines exhibited higher WUE than WT under long-term moderate drought conditions because they maintained robust photosynthesis, effective osmotic adjustment processes, and strong autophagic activity.

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