Changes in photosynthesis during leaf expansion in Corymbia gummifera

2003 ◽  
Vol 51 (1) ◽  
pp. 111 ◽  
Author(s):  
J. S. Choinski Jr ◽  
P. Ralph ◽  
D. Eamus
Keyword(s):  
Stomatal Conductance ◽  
Quantum Yield ◽  
Light Exposure ◽  
New South ◽  
Carbon Assimilation ◽  
Co2 Assimilation ◽  
Anthocyanin Content ◽  
South Wales ◽  
Young Leaves ◽  
Woodland Communities

Growth, pigment levels and various photosynthesis parameters were measured in expanding leaves of Corymbia gummifera (Solander ex Gaertner) Hochreutiner. C. gummifera trees were studied growing in sandstone plateau woodland communities in Royal National Park, New South Wales, in a recently burned open habitat. Young leaves (horizontally oriented to maximise light exposure) were found to be conspicuously red until they reached approximately 75% of their full size. As the leaves expanded, anthocyanin content declined and chlorophyll levels proportionately increased. Young red leaves showed net negative carbon assimilation rates, although CO2 assimilation rate, transpiration rate, stomatal conductance, actual quantum yield of PSII (ΦPSII) and apparent electron transport rate (ETR) all increased in a similar pattern as the leaves expanded. Measurements of maximum quantum yield of dark-adapted leaves (Fv/Fm) were also correlated with leaf area. Younger leaves had lower Fv/Fm ratios than did mature leaves, whether measured at midday or 2 h after sunset, indicating that young leaves exhibited some degree of chronic photoinhibition. It is concluded that C. gummifera exhibits a transient red pattern of anthocyanin expression and that photosynthesis is limited in young leaves because of low stomatal conductance, low chlorophyll content, immature chloroplasts and an attenuation of light caused by anthocyanins.

The tree species preferences of koalas (Phascolarctos cinereus) inhabiting forest and woodland communities on Quaternary deposits in the Port Stephens area, New South Wales

2000 ◽  
Vol 27 (1) ◽  
pp. 1 ◽  
Author(s):  
Stephen Phillips ◽  
John Callaghan ◽  
Valerie Thompson
Keyword(s):  
Tree Species ◽  
New South ◽  
New South Wales ◽  
Eucalyptus Species ◽  
Quaternary Deposits ◽  
Faecal Pellets ◽  
South Wales ◽  
Species Preferences ◽  
Woodland Communities ◽  
Port Stephens

An assessment of the tree species preferences of koalas inhabiting forest and woodland communities growing on Quaternary deposits in the Port Stephens area, New South Wales, was undertaken between November 1994 and March 1996. Using a plot-based methodology, 3847 trees were sampled, comprising 15 Eucalyptus species and 17 species of non-eucalypt. Evidence of tree use by koalas, specifically the presence of koala faecal pellets, was recorded from beneath 10 Eucalyptus species and 9 species of non-eucalypt. Tree species preferences were determined by analyses of log- likelihood ratios derived from data based on the presence/absence of koala faecal pellets, rather than on gross counts. This approach confirmed significant variation in the levels of utilisation amongst and between different tree species, and that two in particular – swamp mahogany (E. robusta) and drooping red gum (E. parramattensis) – were most preferred. Increases in the levels of use of other tree species were also positively associated with the presence of E. robusta and/or E. parramattensis. Levels of utilisation of E. robusta and E. parramattensis did not alter significantly in response to changes in their respective densities, suggesting that the relative abundance of both was important in terms of understanding the carrying capacity of vegetation communities utilised by koalas. The results have established the success with which an enumerative approach to the interpretation of faecal pellet data can be utilised to clarify the tree species preferences of koalas. Application of the approach for habitat assessment and mapping purposes is also discussed.

The effects of feral goats and sheep on the shrub populations in a semi-arid woodland.

1979 ◽  
Vol 1 (4) ◽  
pp. 334 ◽  
Author(s):  
G Harrington
Keyword(s):  
Carrying Capacity ◽  
Seedling Establishment ◽  
New South ◽  
Herb Layer ◽  
South Wales ◽  
Broad Leaf ◽  
Shrub Clearing ◽  
Woodland Communities ◽  
Semi Arid

Shrubs are increasing in density in extensive areas of semi-arid woodland in Queenstand and New South Wales, reducing their carrying capacity for stock and increasing the difficulty of sheep management. A case study is reported in which an area exclosed from grazing increased from 6000 to 9000 shrubslha in 3 years. Grazing by sheep or goats both reduced the establishment ofAcacia aneura (mulga) and Dodonaea 11iscosa (broad-leaf hopbush) seedlings. Cassia spp. (punty and silver cassia), Eremophila sturtii (turpentine), E. rnitchellii (budda) and Geijera parviflora (wilga) were not reduced. Sheep did not affect mature shrubs to any extent. Extremely heavy goat pressure destroyed several problem shrubs, including Acacia arzeura and Dodorzaea viscosa, and reduced Cassia spp. Mechanical shrub-clearing is often followed by sprouting from the roots of some species. Moderate goat pressure failed to control such sprouts; heavy goat pressure eliminated sprouts from E. rnitchellii and G. parviflora but E. sturtii was not eaten, probably because of its higher oilcontent, and increased to 166% of its preclearing density in two years. Mechanical clearing increased shrub seedling establishment four-fold. Future increases in shrub density may be expected in semi-arid woodland communities and goats do not offer an answer to the problem because they are selective between species and because managerially significant reductions in shrub populations can only be achieved at extremely high stocking pressures. The expense of fencing for such a treatment, the damage to the herb layer and the lack of a post treatment management, that would prevent the replacement of palatable shrubs by unpalatable ones, makes it an unsuitable technique for extensively grazed properties.

Temperature Dependence of Whole-Leaf Photosynthesis in Eucalyptus pauciflora Sieb. Ex Spreng

1984 ◽  
Vol 11 (6) ◽  
pp. 519 ◽  
Author(s):  
MUF Kirschbaum ◽  
GD Farquhar
Keyword(s):  
Electron Transport ◽  
Stomatal Conductance ◽  
Temperature Dependence ◽  
Carbon Assimilation ◽  
Co2 Assimilation ◽  
Net Assimilation Rate ◽  
Assimilation Rate ◽  
Component Processes ◽  
Net Assimilation ◽  
Photosynthetic Assimilation

The temperature dependence of net photosynthetic assimilation of CO2 by snowgum (Eucalyptus pauciflora Sieb. ex Spreng.) was investigated. CO2 assimilation was divided into its component processes, stomatal and biochemical. The biochemical limitation was investigated with gas-exchange techniques and found to conform well to a recent model of C3 photosynthesis. In line with the model, net assimilation was further divided into ribulose 1,5-bisphosphate (RuP2) regeneration or electron-transport/photophosphorylation limitation, limitation by RuP2 carboxylase/oxygenase (Rubisco; EC 4.1.1.39) activity, together with loss of CO2 in non-photorespiratory respiration. The estimated temperature dependence of electron transport agreed well with one published for uncoupled electron transport, while the estimated temperature dependence of the catalytic activity of Rubisco was slightly less than that reported from biochemical determinations. The estimated rate of non-photorespiratory respiration was about 0.6 times the rate of respiration at night and appeared to have the same temperature dependence. With this information the temperature dependence of the biochemical limitation was modelled. Stomatal conductance was assumed to follow the theory of constant marginal water cost of carbon assimilation (δE/δA) and net assimilation rate at ambient concentration of CO2 was predicted. It was concluded that, for a given Rubisco activity and RuP2-regeneration capacity, both temperature optimum and net assimilation rate at the optimum temperature increased with increasing stomatal conductance.

Diagnostic leaf nutrient standards for low-chill peaches in subtropical Australia

1997 ◽  
Vol 37 (1) ◽  
pp. 119 ◽  
Author(s):  
D. O. Huett ◽  
A. P. George ◽  
J. M. Slack ◽  
S. C. Morris
Keyword(s):  
New South ◽  
New South Wales ◽  
Leaf Age ◽  
Chemical Properties ◽  
Nutrient Concentrations ◽  
Mature Leaves ◽  
South Wales ◽  
Leaf Nutrient Concentrations ◽  
Young Leaves ◽  
Main Effects

Summary. A leaf nutrient survey was conducted of the low-chill peach cultivars, Flordaprince (October maturing) and Flordagold (mid November–early December maturing) at 3 commercial sites in both northern New South Wales and southern Queensland. Recently mature leaves from the middle third of a current season’s fruiting lateral (spring flush) were sampled at stone hardening and 2-weeks postharvest and of a non-fruiting lateral at maturity of the summer flush (after summer pruning) during the 1992–93 and 1993–94 seasons. At an additional site in New South Wales (Alstonville), leaf nutrient concentrations were also determined on cv. Flordagem (early November maturing) at 2-week intervals during both seasons. Soil (0–30 cm) chemical determinations were conducted at all sites at 2-weeks postharvest Seasonal trends in leaf nutrient composition were associated with a leaf age–maturity effect. As flush leaves matured during spring, and as mature leaves aged after hardening of the summer flush, nitrogen (N) concentration declined and calcium (Ca) concentration increased. Nitrogen and Ca concentrations increased when young leaves produced from the summer flush were sampled. Time of sampling produced the most consistently significant (P<0.05) main effects on leaf nutrient concentration. The 2-week postharvest period was selected as a convenient time to sample—when leaves were of a consistent age and maturity, and the effect of crop load on tree nutrient reserves was still present. Paclobutrazol, which reduces vegetative growth in stonefruit, was applied to all Queensland sites and, as a consequence, mid lateral leaves contained higher (P<0.05) Ca, magnesium (Mg) and chloride (Cl) and lower (P<0.05) N and phosphorus (P) concentrations than leaves from New South Wales sites. State effects can therefore be interpreted as paclobutrazol effects. Cultivar effects (P<0.05) occurred for many leaf nutrients, however, at the 2-week postharvest sampling, concentrations were sufficiently similar to combine as a narrow adequate concentration range for both cultivars. The diagnostic adequate leaf nutrient concentrations were within the range developed for high-chill peaches (Leece et al. 1971) with the exception of lower Ca, lower Mg for New South Wales (both cultivars), lower iron for Flordaprince (both states), higher P for Flordaprince in New South Wales and higher manganese values for Queensland (both cultivars). Regression analyses were conducted between leaf and fruit nutrient concentrations and soil chemical properties. The only consistent result demonstrated that as the soil Ca : Mg ratio increased, leaf Mg concentration decreased exponentially (P<0.001), indicating that the practice of heavy annual agricultural limestone or gypsum applications in the absence of Mg fertiliser, which had been adopted by several growers in the survey, is associated with lower leaf Mg concentrations.

Selection of Grasses With Different Carbon Assimilation Pathways Under Different Sheep Stocking Pressures.

1993 ◽  
Vol 41 (3) ◽  
pp. 327 ◽  
Author(s):  
RW Rogers
Keyword(s):  
Relative Frequency ◽  
New South ◽  
New South Wales ◽  
Carbon Assimilation ◽  
South Wales ◽  
C3 Species ◽  
Stocking Rates ◽  
Selection Of

The path of carbon assimilation was noted for 30 common grasses from unfertilized sheep pastures of the Northern Tablelands of New South Wales. These grasses were then grouped according to their susceptibility to stocking pressure and the frequency and relative frequency of 16 of these related to apparent intensity of stocking about a sheep camp. C3 grass frequency was independent of stocking pressure, but under heavy stocking introduced C3 species replaced native C3 species. C4 NADME species showed an increase in occurrence under high stocking rates, whereas C4 NADPME species showed a decrease in occurrence under high stocking intensity. It is suggested that response to grazing may have been a factor in the evolution of different pathways of carbon assimilation.

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