Influence of light availability on leaf structure and growth of two Eucalyptus globulus ssp. globulus provenances.

Light availability strongly affects leaf structure of the distinctive ontogenetic leaf forms of Eucalyptus globulus Labill. ssp. globulus. Late-maturing plants from St. Marys, Tasmania and early maturing plants from Wilsons Promontory, Victoria (hereafter referred to as Wilsons Prom.) were grown for 9 months in 100, 50 or 10% sunlight. Growth, biomass and leaf area were significantly reduced when plants were grown in 10% sunlight. Provenance differences were minimal despite retention of the juvenile leaf form by the Tasmanian plants throughout the study. The time taken for initiation of vegetative phase change by the Wilsons Prom. saplings increased with decreasing light availability, but the nodal position of change on the main stem remained the same. Both juvenile and adult leaves remained horizontal in low light conditions, but became vertical with high irradiance. Leaf dimensions changed with ontogenetic development, but were unaffected by light availability. Juvenile leaves retained a dorsiventral anatomy and adult Wilsons Prom. leaves retained an isobilateral structure despite a tenfold difference in light availability. Stomatal density and distribution showed ontogenetic and treatment differences. At all irradiances, juvenile leaves produced the smallest stomata and adult leaves the largest stomata. Amphistomy decreased with decreasing irradiance. Detrended, correspondence analysis ordination highlighted the structural changes influenced by ontogenetic development and light availability. Adult leaves had characteristics similar to the xeromorphic, sun-leaf type found in arid, high-light conditions. Although juvenile leaves had characteristics typical of mesomorphic leaves, several structural features suggest that these leaves are more sun-adapted than adult leaves.

Gas exchange responses of two Eucalyptus species to salinity and waterlogging.

The effects of salinity and waterlogging on stomatal conductance, net photosynthesis and transpiration of 3-month-old Eucalyptus camaldulensis Dehnh. and Eucalyptus lesouefii Maiden seedlings were studied under greenhouse conditions. Under non-saline conditions, waterlogging induced stomatal closure in both species. However, the stomata of E. camaldulensis reopened after five weeks, when adventitious roots were produced. Relative to that of controls, height growth of waterlogged seedlings was greater in E. camaldulensis than in E. lesouefii, as were rates of photosynthesis and transpiration. In a freely drained medium, high salinity reduced rates of seedling height growth and photosynthesis, relative to those in controls, less in E. lesouefii than in E. camaldulensis. In both species, height growth, stomatal conductance and photosynthetic rate were lowest under conditions of saline waterlogging.

Experimental assessment of wind erosion after soil stabilization treatments at Eneabba, Western Australia.

Wind tunnel experiments on rehabilitation surfaces at Eneabba, Western Australia evaluated the techniques used by Associated Minerals Consolidated Ltd. (AMC) and Allied Eneabba Ltd. (AEL) to stabilize regions being revegetated following heavy mineral sand mining.Newly landscaped areas proved to be the most erodible, beginning to erode at 9 m sec(-1) and producing a soil flux of 10 kg m(-1) min(-1) at 18 m sec(-1) wind speeds. Sandier, more organically-rich, surfaces in the rehabilitation areas were somewhat less erodible with losses of only 2 kg m(-1) min(-1) at wind speeds of 18 m sec(-1).The mining companies use various nurse crops and top dressing mulch for surface stabilization. Rows of oats, sparse plantings of the grass cultivar "SUDAX" (Dekalb ST6) supplied by Westfarmers Ltd. and applications of Terolas, a cold, bituminous surface binding material supplied by Shell Co. of Australia Ltd., all proved successful in reducing wind erosion in this semi-arid region where more than 25% of summer days experience winds greater than 8 m sec(-1).

Native legume establishment on acidic coal mining overburden at Collie, Western Australia.

Nitrogen is often provided to impoverished overburden dumps through the establishment of legumes. Low indigenous soil nutrient levels, summer drought conditions and an acidic mining overburden represent major obstacles to successful rehabilitation of open-cut coal mining at Collie in southwest Western Australia. In this study,Acacia pulchella, a native Western Australian species often used in rehabilitation of mined lands, was shown to nodulate and grow in coal mining overburden with pH values less than 4.0 under glasshouse conditions. Plant growth (both top and root dry weight), nodule fresh weight, and nodulation success was best at a pH near 5.0, a value only slightly lower than the typical soil pH of the native jarrah (Eucalyptus marginata) forest. Acetylene reduction rates were reduced by acidity and ranged from 8.2 µm C2H4g(-1)hr(-1) at pH 6.77 to 3.0 µm C2H4g(-1)hr(-1) at a pH of 3.98. Four additional plant species were found to occur and to nodulate on acid overburden material at Collie.

Composition and protein quality of honeybee-collected pollen of Eucalyptus marginata and Eucalyptus calophylla.

The composition and protein quality of the two most important Western Australian export-quality pollens were investigated. Crude pollen protein content was 20.6% and 27.9% for Jarrah (Eucalyptus marginata) and Marri (Eucalyptus calophylla), respectively. Lysine was the limiting amino acid relative to the FAO protein scoring pattern (Food and Agriculture Organization of the United Nations), and the amino acid scores were 0.73 and 0.66 for Jarrah and Marri pollen, respectively. Apparent biological value (BV) was 61.7 for Jarrah pollen, 66.9 for Marri pollen and 71.4 for the casein controls. Adjusted protein efficiency ratio (PER) values were 2.5, 1.2 and 1.1 for casein and Jarrah and Marri pollens, respectively. Apparent net protein utilization (NPU) was significantly reduced for both pollens (32.8 for Jarrah and 39.5 for Marri) compared to casein (63.6). The low apparent NPU values result from the relatively low digestibility of pollens. Apparent digestibility was 52 and 59% for Jarrah and Marri pollen compared to 89% for casein. Although both Jarrah and Marri pollen are relatively high in protein and have favorable amino acid patterns, their relatively low digestibility will be a limiting factor in their usefulness as a food for humans and monogastric animals. The proximate analysis and mineral content of the pollens are also presented.

The effects of drought stress on respiration of isolated corn mitochondria.

Mitochondria were isolated from etiolated corn shoots (Zea mays L.) that were stressed to a measured water potential. The rates of mitochondrial respiration in state III, state IV, and without phosphate or ADP on a milligram protein basis decreased as water stress increased with succinate, malatepyruvate, or reduced nicotinamide adenine dinucleotide as substrates. Coupling (as determined by respiratory control and ADP/O ratios) did not decrease with increasing water stress. At water potentials greater than -35 bars all respiration had ceased.