Repair of severe winter xylem embolism supports summer water transport and carbon gain in flagged crowns of the subalpine conifer Abies veitchii

2019 ◽  
Vol 39 (10) ◽  
pp. 1725-1735 ◽  
Author(s):  
Mayumi Y Ogasa ◽  
Haruhiko Taneda ◽  
Hiroki Ooeda ◽  
Akihiro Ohtsuka ◽  
Emiko Maruta
Keyword(s):  
Leaf Nitrogen ◽  
Carbon Gain ◽  
Late Winter ◽  
Leaf Nitrogen Content ◽  
Xylem Embolism ◽  
Coniferous Species ◽  
Abies Veitchii ◽  
Individual Level ◽  
Use Efficiency ◽  
The Individual

Abstract Xylem embolism induced by winter drought is a serious dysfunction in evergreen conifers growing at wind-exposed sites in the mountains. Some coniferous species can recover from winter embolism. The aim of this study was to determine whether wind direction influences embolism formation and/or repair dynamics on short windward and long leeward branches of asymmetrical `flagged' crowns. We analyzed the effect of branch orientation on percentage loss of xylem conductive area (PLC), leaf functional traits and the xylem:leaf area ratio for subalpine, wind-exposed flagged-crown Abies veitchii trees in the northern Yatsugatake Mountains of central Japan. In late winter, the shoot water potential was below −2.5 MPa, and the PLC exceeded 80% in 2-year-old branches, independent of branch orientation within a flagged crown. Both of these parameters almost fully recovered by summer. At branch internodes 4 years of age and older, seasonal changes in PLC were not found in either windward or leeward branches, but the PLC was higher in less leafy windward branches. The leaf nitrogen content and water-use efficiency of mature leaves were comparable between windward branches and leafy leeward branches. The ratio of xylem conductive area to total leaf area was the same for windward and leeward branches. These results indicate that the repair of winter xylem embolism allows leaf physiological functions to be maintained under sufficient leaf water supply, even on winter-wind-exposed branches. This permits substantial photosynthetic carbon gain during the following growing season on both windward and leeward branches. Thus, xylem recovery from winter embolism is a key trait for the survival of harsh winters and to support productivity on the individual level in flagged-crown A. veitchii trees.

scholarly journals Adaptation to Sun and Shade: a Whole-Plant Perspective

1988 ◽  
Vol 15 (2) ◽  
pp. 63 ◽  
Author(s):  
TJ Givnish
Keyword(s):  
Biotic Interactions ◽  
Tree Height ◽  
Light Response ◽  
Leaf Nitrogen ◽  
Compensation Point ◽  
Carbon Gain ◽  
Leaf Nitrogen Content ◽  
Energy Capture ◽  
Irradiance Level ◽  
Whole Plant

Whole-plant energy capture depends not only on the photosynthetic response of individual leaves, but also on their integration into an effective canopy, and on the costs of producing and maintaining their photosynthetic capacity. This paper explores adaptation to irradiance level in this context, focusing on traits whose significance would be elusive if considered in terms of their impact at the leaf level alone. I review traditional approaches used to demonstrate or suggest adaptation to irradiance level, and outline three energetic tradeoffs likely to shape such adaptation, involving the economics of gas exchange, support, and biotic interactions. Recent models using these tradeoffs to account for trends in leaf nitrogen content, stornatal conductance, phyllotaxis, and defensive allocations in sun v. shade are evaluated. A re-evaluation of the classic study of acclimation of the photosynthetic light response in Atriplex, crucial to interpreting adaptation to irradiance in many traits, shows that it does not completely support the central dogma of adaptation to sun v. shade unless the results are analysed in terms of whole-plant energy capture. Calculations for Liriodendron show that the traditional light compensation point has little meaning for net carbon gain, and that the effective compensation point is profoundly influenced by the costs of night leaf respiration, leaf construction, and the construction of associated support and root tissue. The costs of support tissue are especially important, raising the effective compensation point by 140 �mol m-2 s-1 in trees 1 m tall, and by nearly 1350 �mol m-2 s-1 in trees 30 m tall. Effective compensation points give maximum tree heights as a function of irradiance, and shade tolerance as a function of tree height; calculations of maximum permissible height in Liriodendron correspond roughly with the height of the tallest known individual. Finally, new models for the evolution of canopy width/height ratio in response to irradiance and coverage within a tree stratum, and for the evolution of mottled leaves as a defensive measure in understory herbs, are outlined.

Photosynthesis - stomatal conductance model LEAFC3-N: specification for barley, generalised nitrogen relations, and aspects of model application

2008 ◽  
Vol 35 (10) ◽  
pp. 797 ◽  
Author(s):  
Johannes Müller ◽  
Henning Braune ◽  
Wulf Diepenbrock
Keyword(s):  
Stomatal Conductance ◽  
Growth Models ◽  
Leaf Nitrogen ◽  
Carbon Gain ◽  
Model Parameters ◽  
Leaf Nitrogen Content ◽  
Time Step ◽  
Close Range ◽  
Crop Growth Models ◽  
Parameter Values

We discuss a generalised formulation of the nitrogen-sensitive photosynthesis−stomatal conductance model LEAFC3-N to be used as a submodel of functional–structural plant models (FSPMs) or traditional crop growth models for C3-crops. Based on a parameterisation study for barley, we demonstrate that the large variation of characteristics related to potential leaf photosynthesis and stomatal conductance, along with different factors, can be accounted for by introducing functions that relate parameter values to nitrogen contents. These relationships follow the same pattern for different C3 crops, and their parameters are in close range. The accuracy of the parameters and the minimum simulation time step required for reliable predictions of the integrated diurnal carbon gain (IDC) is assessed. For IDC predictions with an accuracy of about ±5%, the accuracy of the slope of the relationship between maximum carboxylation rate and leaf nitrogen content should be of similar order. For other key model parameters, an error of ±20% or even greater may be tolerated. A time step of 1–2 h will be sufficient to predict IDC with an accuracy of about ±5%.

Leaf Photosynthesis and Drought Adaptation in Field-Grown Oilseed Rape (Brassica napus L.)

1996 ◽  
Vol 23 (5) ◽  
pp. 631 ◽  
Author(s):  
CR Jensen ◽  
VO Mogensen ◽  
G Mortensen ◽  
MN Andersen ◽  
JK Schjoerring ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Nitrogen Content ◽  
Leaf Area ◽  
Leaf Nitrogen ◽  
C3 Plants ◽  
Soil Drying ◽  
Leaf Nitrogen Content ◽  
Drought Adaptation ◽  
Brassica Napus L ◽  
Use Efficiency

Photosynthesis and drought adaptation in leaves of field grown rape (Brassica napus L. cv. Global) were investigated in 1992 under temperate climatic conditions in plants grown in lysimeters in a sand and in a loam soil. Light-saturated net photosynthesis (Amax), leaf conductance to water vapour (ge), leaf water potential (Ψe), leaf osmotic potential at full turgor (Ψπ100), specific leaf area (SLA), spectral reflection index (RI) used as a measure of leaf area, and leaf nitrogen content, were determined in irrigated plants and in plants exposed to soil drying. In the early growth stages before flowering, Amax was 35-45 μmol m-2 s-1 and ge was 1-1.5 mol m-2 s-1. Maximum rates of CO2 assimilation greater than 30 μmol m-2 s-1 were obseved for up to 19 days. Stomata partly closed in ageing leaves maintaining a constant CI/Ca ratio. Both photosynthetic nitrogen use efficiency (NUE; Amax per unit of nitrogen) and photosynthetic water use efficiency (WUE; Amax/ge) were high compared with efficiencies of stems and husks and of other C3 plants. In bracts Amax and ge were 10-15 μmol m-2 s-1 and 0.2-0.7 mol mol m-2 s-1, respectively. Both Amax and ge varied linearly with leaf nitrogen content. When soil water was depleted, both Ψπ100 and RI decreased relative to controls on both soil types before any significant decrease in Ψπ occurred. On loam with slow soil drying SLA, ge and Amax decreased before any significant decrease in Ψe occurred. We suggest that these responses might have been triggered by a non-hydraulic signal transmitted from the roots. When water was more depleted, rape maintained positive turgor down to Ψe of -1.6 MPa. Rape had a high TW/DW ratio (9-11) and a 6 limited ability to adjust osmotically, ΔΨe100 being at most 0.3-0.4 MPa.

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