Effects of drought and high temperature on grain growth

Abstract The effects of two levels of temperature and of water supply on grain development of wheat (cv. Warigal) were studied by imposing treatments during the early or late period of cell division. High temperature (28OC day/2O0C night) accelerated development of the grain. Dry matter accumulation and cell division proceeded at a higher rate but had a shorter duration in the high temperature treatments. Maximum cell number, final cell size and the number of large starch granules per cell were not significantly reduced by high temperature. Drought and drought X high temperature reduced the storage capacity of the grain, with a decrease in number of cells and starch granules in the endosperm. Cell size was also reduced when treatments were imposed late during cell division. Duration of dry matter accumulation and cell division was reduced in the drought and drought X high temperature treatments. The combined effects of drought and high temperature were much more severe than those of each separate treatment. The amount of sucrose per cell was similar in all treatments. It appears unlikely that the supply of sucrose to the endosperm cells is the main limiting factor of dry matter accumulation in both drought and high temperature treatments

Identifying allelopathic compounds emitted by Pittosporum undulatum in Eucalypt forests

Changing climatic conditions played a major role in plants evolution and could modify the composition, structure and functionality of native plant communities, favoring invasive species. Studies conducted in south-eastern Australia have reported Pittosporum undulatum, a native tree, to be an aggressive invader of Eucalyptus forests. We tested the hypothesis that its negative impact on floristic diversity is due to the release of allelopathic compounds inhibiting the germination and growth of other plants. Thus, we compared the germination of Pittosporum undulatum, Eucalyptus ovata and lettuce on different substrates. Seeds were watered with leachates made from fresh P. undulatum leaves, litter collected from underneath P. undulatum or Eucalyptus trees, or distilled water.P. undulatum seeds germinated more slowly than the other two species, however showed faster growth rates. E. ovata mortality rates seedlings were very high immediately after germination. While there were no significant treatment effects on germination rates, there were differences in morphology. The root system, in lettuce and E. ovata, was short and damaged when watered with fresh P. undulatum leaves extract.Additionally, we investigated the possible emission of specific Biogenic Volatile Organic Compounds (BVOCs) which could have ecological functions or increase P. undulatum stress resistance. Using Solid Phase Microextraction (SPME) fibers, BVOCs were collected and analysed using Gas chromatography-mass spectrometry (GC-MS) to compare the emissions in eucalypt forests with and without P. undulatum. The main difference between the two sites was the higher D-limonene and α-pinene aerial concentration in P. undulatum infested sites.Our results suggest that the high invasiveness of P. undulatum is mainly related to morphological and physiological characteristics rather than to allelopathic compounds emitted by this species. Additionally, the greater emission of D-limonene and α-pinene from P. undulatum compared to eucalypts could increase the resistance to abiotic stresses, such as drought or ozone

Design for learning - a case study of blended learning in a science unit

Making material available through learning management systems is standard practice in most universities, but this is generally seen as an adjunct to the ‘real’ teaching, that takes place in face-to-face classes. Lecture attendance is poor, and it is becoming increasingly difficult to engage students, both in the material being taught and campus life. This paper describes the redevelopment of a large course in scientific practice and communication that is compulsory for all science students studying at our Melbourne and Malaysian campuses, or by distance education. Working with an educational designer, a blended learning methodology was developed, converting the environment provided by the learning management system into a teaching space, rather than a filing system. To ensure focus, topics are clustered into themes with a ‘question of the week’, a pre-class stimulus and follow up activities. The content of the course did not change, but by restructuring the delivery using educationally relevant design techniques, the content was contextualised resulting in an integrated learning experience. Students are more engaged intellectually, and lecture attendance has improved. The approach we describe here is a simple and effective approach to bringing this university’s teaching and learning into the 21st century

Changes in Nutritional Value of Cyanogenic Trifolium Repens Grown at Elevated Atmospheric CO2

Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric carbon dioxide on the toxicity of the important pasture crop, Trifolium repens L. (clover). Shoots of T. repens contain cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. The ability of animals to tolerate cyanogenic compounds is dependent, in part, on their overall protein intake. We grew T. repens communities at ambient and approximately twice-ambient CO2 in a controlled environment greenhouse experiment. We found that the ratio of total cyanogenic glycosides to total protein ratio was nearly two times higher in leaves of T. repens grown at elevated CO2. This study highlights the importance of assessing the nutritive value of this and other plants in response to rising CO2 so that steps can be taken to address any adverse consequences for herbivores

Effects of Salinity on the Growth and Nutrition of Taro (Colocasia esculenta): Implications for Food Security

Taro (Colocasia esculenta (L.) Schott) is a staple food crop in the Asia-Pacific region in areas where rising sea levels are threatening agricultural production. However, little is known about its response to salinity. In this study, we investigated the effects of salinity on the growth, morphology, physiology, and chemical traits of taro to predict the impacts of rising sea levels on taro production and nutritional value in the Pacific. We grew taro (approximately 4 months old) with a range of NaCl treatments (0–200 mM) for 12 weeks. Full nutrient, micronutrient, and secondary metabolite analyses were conducted, including measures of calcium oxalate (CaOx), an irritant that reduces palatability. Significant reductions in growth and biomass were observed at and above 100 mM NaCl. Concentrations of macro- and micronutrients, including sodium, were higher on a per mass basis in corms of plants experiencing salt stress. Foliar sodium concentrations remained stable, indicating that taro may utilize a salt exclusion mechanism. There was a large amount of individual variation in the concentrations of oxalate and phenolics, but overall, the concentrations were similar in the plants grown with different levels of salt. The total contents of CaOx and phenolics decreased in plants experiencing salt stress. Taro’s ability to survive and produce corms when watered with a 200 mM NaCl solution places it among the salt-tolerant non-halophytes. The nutritional quality of the crop is only marginally affected by salt stress. Taro is, therefore, likely to remain a useful staple in the Pacific region in the future

Cyanide Content of Cassava Food Products Available in Australia

In 2009, Food Standards Australia New Zealand set a total cyanide content limit of 10 ppm for ready-to-eat cassava products to address food safety concerns about cyanogenic glucosides in cassava. This study surveys a range of cassava food products available in Melbourne, Australia, ten years after the implementation of these regulations. Of all the products tested, the mean cyanide content was greatest in ready-to-eat cassava chips (48.4 ppm), although imported ready-to-eat products had a higher mean cyanide content (95.9 ppm) than those manufactured in Australia (1.0 ppm). Cyanide was detected in frozen cassava products (grated mean = 12.9 ppm; whole root mean = 19.8 ppm), but was significantly reduced through processing according to packet instructions in both product types. Three methods were used to quantify total cyanide content: the evolved cyanide method, the picrate absorbance method and the picrate chart method, with satisfactory agreement between methods. The picrate absorbance and chart methods reported mean cyanide contents 13.7 ppm and 23.1 ppm higher, respectively, than the evolved cyanide method. Our results reaffirm the need for the ongoing testing of cassava food products, especially ready-to-eat products whose cyanide content will not be reduced before consumption

Effects of Salinity on the Growth and Nutrition of Taro (<i>Colocasia esculenta</i>): Implications for Food Security

Taro (Colocasia esculenta (L.) Schott) is a staple food crop in the Asia-Pacific region in areas where rising sea levels are threatening agricultural production. However, little is known about its response to salinity. In this study, we investigated the effects of salinity on the growth, morphology, physiology, and chemical traits of taro to predict the impacts of rising sea levels on taro production and nutritional value in the Pacific. We grew taro (approximately 4 months old) with a range of NaCl treatments (0–200 mM) for 12 weeks. Full nutrient, micronutrient, and secondary metabolite analyses were conducted, including measures of calcium oxalate (CaOx), an irritant that reduces palatability. Significant reductions in growth and biomass were observed at and above 100 mM NaCl. Concentrations of macro- and micronutrients, including sodium, were higher on a per mass basis in corms of plants experiencing salt stress. Foliar sodium concentrations remained stable, indicating that taro may utilize a salt exclusion mechanism. There was a large amount of individual variation in the concentrations of oxalate and phenolics, but overall, the concentrations were similar in the plants grown with different levels of salt. The total contents of CaOx and phenolics decreased in plants experiencing salt stress. Taro’s ability to survive and produce corms when watered with a 200 mM NaCl solution places it among the salt-tolerant non-halophytes. The nutritional quality of the crop is only marginally affected by salt stress. Taro is, therefore, likely to remain a useful staple in the Pacific region in the future

Integrating the Passenger-Driver hypothesis and plant community functional traits to the restoration of lands degraded by invasive trees

Our study examined the response of ten plant communities across Victoria, Australia to the infestation and subsequent removal of Pittosporum undulatum, a tree native to south Eastern Australia that is increasingly viewed as an invader within and particularly beyond its native range. At sites where P. undulatum removal has occurred over a 1–14 year period, species richness, canopy cover and functionality were compared against nearby invaded and remnant temperate Eucalyptus bushland, so as to gauge the direction and magnitude of community change over time. There are four main findings: (1) Low levels of native and non-native species richness and canopy cover were recorded at communities impacted by dense P. undulatum populations; (2) very low densities of P. undulatum at all cleared areas after removal; (3) removing P. undulatum caused an increase in species richness, particularly for native species; and (4) over time, management intervention lead to increasing similarity in community composition and function between cleared areas and remnant controls. Our case study demonstrates how the Passenger-Driver hypothesis (PDH) can be used effectively to understand the mechanisms at play between native and exotic drivers of community composition and function. Results are discussed in relation to how ecological theory can be applied to inform and improve invasive species management and restorative actions