The effect of wind gusts on leaf growth and foliar water relations of aspen

Oecologia ◽  
1978 ◽  
Vol 34 (1) ◽  
pp. 101-106 ◽  
Author(s):  
W. Flückiger ◽  
J. J. Oertli ◽  
H. Flückiger-Keller
Keyword(s):  
Water Relations ◽  
Leaf Growth ◽  
Wind Gusts

THE WATER RELATIONS OF RUBBER (HEVEA BRASILIENSIS): A REVIEW

2011 ◽  
Vol 48 (2) ◽  
pp. 176-193 ◽  
Author(s):  
M. K. V. CARR
Keyword(s):  
East Asia ◽  
Water Relations ◽  
Leaf Growth ◽  
Water Productivity ◽  
Stomatal Closure ◽  
Rubber Tree ◽  
Background Information ◽  
South East Asia ◽  
Water Requirements ◽  
Water Potentials

SUMMARYThe results of research done on water relations of rubber are collated and summarised in an attempt to link fundamental studies on crop physiology to crop management practices. Background information is given on the centres of origin (Amazon Basin) and production of rubber (humid tropics; south-east Asia), but the crop is now being grown in drier regions. The effects of water stress on the development processes of the crop are summarised, followed by reviews of its water relations, water requirements and water productivity. The majority of the recent research published in the international literature has been conducted in south-east Asia. The rubber tree has a single straight trunk, the growth of which is restricted by ‘tapping’ for latex. Increase in stem height is discontinuous, a period of elongation being followed by a ‘rest’ period during which emergence of leaves takes place. Leaves are produced in tiers separated by lengths of bare stem. Trees older than three to four years shed senescent leaves (a process known as ‘wintering’). ‘Wintering’ is induced by dry, or less wet, weather; trees may remain (nearly) leafless for up to four weeks. The more pronounced the dry season the shorter the period of defoliation. Re-foliation begins before the rains start. The supply of latex is dependent on the pressure potential in the latex vessels, whereas the rate of flow is negatively correlated with the saturation deficit of the air. Radial growth of the stem declines in tapped trees relative to untapped trees within two weeks of the start of tapping. Roots can extend in depth to more than 4 m and laterally more than 9 m from the trunk. The majority of roots are found within 0.3 m of the soil surface. Root elongation is depressed during leaf growth, while root branching is enhanced. Stomata are only found on the lower surface of the leaf, at densities from 280 to 700 mm−2. The xylem vessels of rubber trees under drought stress are vulnerable to cavitation, particularly in the leaf petiole. By closing, the stomata play an essential role in limiting cavitation. Clones differ in their susceptibility to cavitation, which occurs at xylem water potentials in the range of −1.8 to −2.0 MPa. Clone RRII 105 is capable of maintaining higher leaf water potentials than other clones because of stomatal closure, supporting its reputation for drought tolerance. Clones differ in their photosynthetic rates. Light inhibition of photosynthesis can occur, particularly in young plants, when shade can be beneficial. Girth measurements have been used to identify drought-tolerant clones. Very little research on the water requirements of rubber has been reported, and it is difficult to judge the validity of the assumptions made in some of the methodologies described. The actual evapotranspiration rates reported are generally lower than might be expected for a tree crop growing in the tropics (<3 mm d−1). Virtually no research on the yield responses to water has been reported and, with the crop now being grown in drier regions, this is surprising. In these areas, irrigation can reduce the immaturity period from more than 10 years to six years. The important role that rubber plays in the livelihoods of smallholders, and in the integrated farming systems practised in south-east Asia, is summarized.

scholarly journals WATER RELATIONS AND LEAF GROWTH

1985 ◽  
pp. 131-138 ◽  
Author(s):  
G. Taylor ◽  
W.J. Davies
Keyword(s):  
Water Relations ◽  
Leaf Growth

Water Relations of Expanding Leaves

1986 ◽  
Vol 13 (1) ◽  
pp. 45 ◽  
Author(s):  
EWR Barlow
Keyword(s):  
Water Stress ◽  
Water Relations ◽  
Leaf Development ◽  
Leaf Growth ◽  
Water Status ◽  
Morphological Difference ◽  
Growth Patterns ◽  
Expansion Phase ◽  
Turgor Maintenance ◽  
Yield Threshold

The reactivity of leaf growth to changes in plant water status has been analysed in terms of leaf development, water transport and turgor. The different growth patterns of monocotyledonous and dicotyledonous leaves result in fundamental differences in the water relations of expanding leaves. Most monocotyledonous leaf cells complete their expansion phase within the protective older leaf bases, while the majority of dicotyledonous leaf cells expand in an exposed evaporative environment. The consequence of this morphological difference is that expanding monocotyledonous leaves behave similarly to other enclosed tissue during water stress by exhibiting turgor maintenance through osmotic adjustment. Expanding dicotyledonous leaves do not exhibit this response. The maintenance of turgor in monocotyledons in the absence of leaf expansion suggests that growth is controlled by the yield threshold of the cell wall during episodes of water stress.

Time Trends for Change in Osmotic Adjustment and Water Relations of Leaves of Cenchrus ciliaris During and After Water Stress

1983 ◽  
Vol 10 (1) ◽  
pp. 15 ◽  
Author(s):  
JR Wilson ◽  
MM Ludlow
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Water Relations ◽  
Osmotic Adjustment ◽  
Leaf Growth ◽  
Weight Ratio ◽  
Bound Water ◽  
Arid Environment ◽  
Leaf Water ◽  
Buffel Grass

Buffel grass was subjected to a soil drying cycle for 5 weeks in a semi-arid environment. As water stress developed, the leaf water relations characteristics of these plants (Dry treatment) were compared with those of irrigated plants (Wet treatment). Leaf water potential (Ψ) of the Dry treatment measured at 1400 h decreased to a minimum of -6.9 MPa. The stressed leaves adjusted osmotically, with the osmotic potential at full turgor (Ψπ100) decreasing (becoming more negative) linearly with time (0.017 MPa day-1) and with decreasing water potential measured at 1400 h (0.11 MPa per 1 MPa decrease in Ψ). Maximum osmotic adjustment (Ψπ100 Wet -Ψπ100 Dry) was 0.66 MPa, and this change together with lower cell wall elasticity decreased by 1.03 MPa the water potential (Ψ0) at which the stressed leaves lost turgor. Differences between the stress- acclimated Dry leaves and the Wet leaves in bound water, turgid weight:dry weight ratio and the relative water content at which they reached zero turgor were small and inconsistent. At 18 days after rewatering, the Ψπ100 value of acclimated leaves was still 0.18 MPa lower than that of the control leaves. The substantial shift in Ψ0 gained the stress-acclimated leaves only one extra day before they lost turgor at 1400 h, and only 2.5 extra days before being permanently wilted. This small gain in time and the rapid cessation of leaf growth even before positive turgor was completely lost suggests that osmotic adjustment may not contribute greatly to continued leaf growth in water-stressed plants of buffel grass.

scholarly journals Water relations and leaf growth rate of three Agropyron genotypes under water stress

BIOCELL ◽  
2002 ◽  
Vol 26 (3) ◽  
pp. 309-317 ◽  
Author(s):  
MAR虯 G. GARC虯 ◽  
CARLOS A. BUSSO ◽  
PABLO POLCI ◽  
NORBERTO L. GARC虯 GIROU ◽  
VIVIANA ECHENIQUE
Keyword(s):  
Growth Rate ◽  
Water Stress ◽  
Water Relations ◽  
Leaf Growth

The Influence of Salinity on Growth, Water Relations and Photosynthesis in Diplachne fusca (L.) P. Beauv. Ex Roemer & Schultes

1990 ◽  
Vol 17 (6) ◽  
pp. 675 ◽  
Author(s):  
BA Myers ◽  
TF Neales ◽  
MB Jones
Keyword(s):  
Growth Rate ◽  
Water Relations ◽  
Growth Rates ◽  
High Salinity ◽  
Leaf Growth ◽  
Intercellular Co2 Concentration ◽  
Carboxylation Efficiency ◽  
Initial Slope ◽  
Leaf Photosynthesis ◽  
Salinity Levels

The responses to increasing salintiy (in the range 0-420 mol m-3 NaCl) of an Australian accession of the halophytic grass, Diplachne fusca, have been studied in two experiments; in terms of growth, water relations, ion uptake and leaf photosynthesis. Twenty-one to 41 days after salinisation, plant dry weight, leaf area and relative growth rate were decreased at salinities at and above 300 mol m-3. Although salinity in the range 0-200 mol m-3 did not significantly affect growth rate, the highest value was at 200 mol m-3. Towards the end of the sampling period, a recovery of leaf growth rates was greater in plants at salinity levels of 90-200 mol m-3. The salt tolerance of this accession is similar to that reported for other populations of this species. As salinity in the root environment was increased, the osmotic potential of the leaf sap (Ψs) and the difference between leaf water potential and Ψs increased progressively with each harvest. There was no evidence that a lack of a capacity to adjust osmotically was related to the observed inhibition of growth at high salinity levels. It was confirmed that D. fusca possessed a C4 mode of leaf photosynthesis: the maximum assimilation rate (A) observed was high (>50 μmol m-2 s-1), the operating intercellular CO2 concentration (Ci) was approximately 140 μmol mol-1, the initial slope of the A v. CI curve ('carboxylation efficiency') was steep (1.24 μmol m-2 s-1) and the optimum leaf temperature for photosynthesis was approximately 45°C. At high salinities leaf conductance (g) was reduced by 78%. Using an analysis of A v. I and A v. CI relationships, the components of the 'photosynthetic capacity' of the mesophyll reduced by high salinity were Amax, carboxylation efficiency and photorespiration rate. There was no consistent relationship, at three salinity levels, between growth rates and Amax and carboxylation efficiency. It appears unlikely, therefore, that the primary inhibitory effects of salinity on growth are attributable to effects on leaf photosynthetic processes.

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