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Alfalfa (Medicago sativa L.) is a nutritious forage plant in dryland regions with strong drought tolerance and broad adaptability. To understand the architectural characters and physiological functions of the root systems in response to different drought stress and rehydration, two experiments were conducted in a glasshouse. Experiment 1 used three alfalfa cultivars and four soil moisture treatments in a split-plot design with four replicates to investigate the response of root systems of different alfalfa cultivars to drought stress and subsequent rehydration. Experiment 2 used one alfalfa cultivar and four soil moisture treatments in a randomized complete block (RCB) design with three replicates to measure reactive oxidant species and antioxidant defense systems of alfalfa root. The soil moisture treatments included (1) 75&ndash, 80% of the water-holding capacity (CK), (2) 60&ndash, 65% of the water-holding capacity and subsequent rehydration to 75&ndash, 80% of the water-holding capacity, (3) 45&ndash, 50% of the water-holding capacity and subsequent rehydration to 60&ndash, 65% and 75&ndash, and (4) 30&ndash, 35% of the water-holding capacity and subsequent rehydration to 45&ndash, 50%, 60&ndash, 80% of the water-holding capacity. Our results demonstrated that plants had higher root biomasses (mean = 0.77 g), fractal dimensions (1.47), fractal abundances (3.84), and branching ratios (0.39) under severe water deficit and rehydration than under less stressful soil moisture conditions. Plant root systems tended to exhibit herringbone branching (Topological Index = 0.63) when soil moisture was at 60&ndash, 65% water-holding capacity with the soil being then rehydrated, whereas they tended to have a smaller lateral root length, root surface area, root volume, and branching ratio and larger root diameter under more favorable soil moisture conditions for less stressful soil moisture treatments. Severe water stress and subsequent considerably improved superoxide (O2&minus, ) generation rate, the content of hydrogen peroxide (H2O2) and Malondialdehyde (MDA), and non-enzyme antioxidant glutathione (GSH), and reduced the content of ascorbate (AsA) and activity of catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX). It is concluded that Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) exhibited higher drought resistances than cv Golden empress (GE) using topological and fractal analyses. This could be a key contributor to altering optimum soil moisture conditions and screening alfalfa cultivars based on root system architecture and antioxidant defense systems. The molecular functions warrant further investigation which could help explain the observed root phenotypes after drought conditions and rehydration.

Lucerne (Medicago sativa L.) persistence is important for farming systems in south east Australia. Defoliation of lucerne that is too frequent (arguably more than once every six weeks) reduces yield and accelerates stand decline. Three experiments were conducted in south east Australia (Burraja, New South Wales, Rutherglen and Hamilton, Victoria) to investigate different cutting regimes on lucerne persistence. At Burraja lucerne was cut 16 (lax) or 33 (severe) times over three years at different plant densities. At Rutherglen and Hamilton lucerne was cut every 21 days (short rotation), every 42 days (long rotation), when new shoots (2.5 cm long) emerged (new shoots) or cutting when new shoots emerged but allowing the lucerne to flower in autumn (new shoots flowering). It was hypothesised that the frequent cutting of lucerne would result in lower plant densities. At Burraja there was little difference between treatments at any density or assessment. At Hamilton, apart from the assessment in June 2016, there was no difference (p &gt, 0.1) between treatments. At Rutherglen, there was no difference (p &gt, 0.1) between treatments at any assessment although plant numbers declined in 2016 from waterlogging. The results provide evidence that lucerne has intrinsic mechanisms that protect it from cutting, often at short intervals, thus promoting its persistence over three to four-year periods.

Anemone flaccida Fr. Schmidt is a traditional medicinal herb in southwestern China and has multiple pharmacological effects on bruise injuries and rheumatoid arthritis (RA). A new drug with a good curative effect on RA has recently been developed from the extract of A. flaccida rhizomes, of which the main medicinal ingredients are triterpenoid saponins. Due to excessive exploitation, the wild population has been scarce and endangered in a few of its natural habitats and research on the cultivation of the plant commenced. Studies on the gene expressions related to the biosynthesis of triterpenoid saponins are not only helpful for understanding the effects of environmental factors on the medicinal ingredient accumulations but also necessary for monitoring the herb quality of the cultivated plants. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) as a sensitive and powerful technique has been widely used to detect gene expression across tissues in plants at different stages, however, its accuracy and reliability depend largely on the reference gene selection. In this study, the expressions of 10 candidate reference genes were evaluated in various organs of the wild and cultivated plants at different stages, using the algorithms of geNorm, NormFinder and BestKeeper, respectively. The purpose of this study was to identify the suitable reference genes for RT-qPCR detection in A. flaccida. The results showed that two reference genes were sufficient for RT-qPCR data normalization in A. flaccida. PUBQ and ETIF1a can be used as suitable reference genes in most organs at various stages because of their expression stabilitywhereas the PUBQ and EF1Α genes were desirable in the rhizomes of the plant at the vegetative stage.

Integrated crop-livestock systems (ICL) have played an important role in human civilisation and have dominated the broadacre agricultural production system in the wheat-sheep zone of Australia. Over the past couple of decades, an increase in grain prices and decline in wool prices have led to the expansion of cropping into the high rainfall zone (HRZ) in southern Australia. While there has been a great deal of research into integrated crop-livestock systems for the medium to low rainfall environments in the wheat-sheep zone, there is much less information and many challenges confronting farmers to effectively integrate crops into the grazing systems in the high rainfall zone due to climatic and environmental differences and the complexity of the systems in Australia. This paper reviews the benefits of integrated crop-livestock systems and the challenges in implementing and managing these systems based on current Australian and international knowledge. The concept, types and terminology of integrated crop-livestock systems are discussed to provide greater clarity. Plant species, particularly annual and perennial legumes, are reviewed to find species with potential for use in integrated crop-livestock systems. Major gaps and opportunities for further research and development are identified, and recommendations proposed for developing effective integrated crop-livestock systems for the HRZ. These include: 1) Targeted RD 2) Biophysical and bio-economic modelling using current knowledge from the HRZ and other environments to guide future research; 3) Studies on N fixation, transfer and losses to develop strategies to balance N cycling and reduce N losses; 4) Development of compatible species/cultivars for ICL systems in the HRZ; 5) Management of waterlogging through ICL in the HRZ; 6) Effective stubble management to minimise the negative impact on crops and pastures; 7) Integrated research on grain yield reduction in crop-pasture intercropping, a potentially major type of ICL systems in the HRZ; and 8) Effective control of weeds, pests and diseases in ICL systems for the HRZ.

Cocksfoot (Dactylis glomerata L.) is a widely grown temperate perennial grass for livestock production worldwide. Recent studies have observed that cocksfoot plants inhibit the growth and development of companion and volunteer species. However, there has been little research on how this inhibitory effect happens and whether it occurs widely or on a limited number of species only. The aim of the study was to quantify the inhibitory or allelopathic effect and its possible role in the effect of cocksfoot on the growth and seed germination of a range of grass, legume and volunteer species. Three experiments were conducted: Experiment 1 was a greenhouse experiment that used 4 grass and legume monocultures and 9 mixtures with 3 mixtures ratios; Experiment 2 was a lab experiment that used different concentrations of cocksfoot rhizosphere extracts to test the germination and seedling growth of 5 commonly sown pasture species; Experiment 3 was a field experiment to validate the inhibitory effects of cocksfoot as shown in Experiments 1 and 2 under field conditions. The results demonstrated that cocksfoot had strong inhibitory effects on all the species tested in this study although the magnitude varied between species. On average, the cocksfoot percentage in mixtures was increased by 120% for herbage accumulation, and 168% for tiller density relative to its designed proportions in mixtures under field conditions. Cocksfoot rhizosphere extracts considerably reduced the germination and seedling growth of all tested species except lucerne that had lower seedling vigour. It is concluded that cocksfoot roots may have produced metabolites that inhibit the seed germination and plant growth of companion or volunteer species. This could be a contributor to the superior persistence of the species and have significant practical implications on weed control. The biochemical compounds of cocksfoot root metabolites and their functions deserve further investigation.

Australia is one of the hottest and driest continents in the world in terms of duration/ intensity of heat and annual rainfall. Extreme air temperatures (> 45°C) have been recorded at almost all stations more than 150 km from the coast and in many areas on the northwest and southern coasts (NATMAP, 1986). Half of Australia’s total land area has an average annual rainfall of < 300 mm (Fig. 15.1); consequently, a large part of central Australia is desert or semi-arid. The northern part of the continent is largely tropical rainforests, tropical and sub-tropical grasslands and desert. The more intensive farming systems are applied in the coastal regions and the south-east and south-west corners of Australia with a temperate climate (Nie and Norton, 2009; Nie et al., 2016).

Plants of Potamogeton crispus, a submersed macrophyte, were cultivated in the water free of algae and containing different concentrations of inorganic nitrogen (0.2 and 20 mg N L−1) and phosphorus (0.02 and 2.0 mg P L−1). The changes in plant growth and turion formation and the carbohydrate contents in plants and turions were investigated, and the endogenous abscisic acid (ABA) levels and the expressions of ABA biosynthetic genes in the stem apices analysed. The purpose of this study was to clarify the effects of water N and P levels on the plant growth and propagation capacity of P. crispus and to reveal whether ABA metabolism is involved in the turion formation of the plant under different ambient nutritional conditions. Finding the biomass of plants was not affected by the water N and P concentrations, except for those grown in water with low N and high P that had higher biomass accumulation and carbohydrate contents. Higher P promoted plant N uptake from the water, but higher N inhibited plant P uptake from the water with high P. High water N significantly delayed the turion initiation of P. crispus. Plants formed more apical turions with a greater size and more carbohydrate reserves when grown in water containing low N and low P, which leads to higher propagation of the plant population. The combination of high N and high P in water inhibited the formation and growth of turions, resulting in significant attenuation of the propagation capacity. High N combinated with low P or high P combinated with low N promoted the formation of more axillary turions and total turions but inhibited the turion growth. ABA levels and the expressions of ABA biosynthetic genes in stem apices at the turion initiation were changed by water N and P levels. The elevated ABA levels were consistent with the increased total turion number per plant when grown in the water with low N and/ or low P. The up-regulation of ZEP (zeaxanthin epoxidase) or NCED6 (9-cis-epoxycarotenoid dioxygenase6) may account for the ABA accumulation in the stem apices. The involvement of ABA metabolism in the turion formation relies on varying gene expression patterns when the plant grows in water containing different N and P concentrations.

Direct sown oilseed rape has been rapidly developed in recent years due to increasing shortage of labor force in the winter oilseed rape ( Brassica napus L.) region of Yangtze River Basin. However, the appropriate nitrogen management of the crop has not yet been established, resulting in poor seed yield. Two experiments were conducted, including a pot trial to elucidate the N utilization in different growth periods under sufficient supplies of N and other nutrients, and a field experiment to study the effects of N application rates at different stages on plant development, biomass production, seed yield and N use efficiency of direct sown oilseed rape. The results showed that N applications at different stages extended the growth period of the crop. The vegetative growth was extended more than the reproductive growth by N applied at early stages. Nitrogen application promoted the plant growth center/s leading to high biomass accumulations in different periods. Higher pre-sowing N rates prolonged the fast biomass accumulation period and increased the fastest accumulation speed. The seed yield and NUE of the crop were improved by N applied prior to sowing and at the initiation of stem elongation. The results suggest that, relatively high N rate but not exceeding 135 kg N ha −1 applied at pre-sowing, 67.5–90 kg N ha −1 at the initiation of stem elongation, and appropriate rates depending on the seedling growth at 5-leaf stage were optimum N fertilizer strategies to achieve high production for the direct sown winter oilseed rape in Yangtze River Basin.

A field grazing experiment was conducted in Jingtai County, Gansu Province, China, from 2003 to 2010. The grazing intensity treatments included light grazing (LG, 0.45 sheep unit/ha), moderate grazing (MG, 0.75 sheep unit/ha), heavy grazing (HG, 1.50 sheep unit/ha), and no grazing (NG). Soil physical, chemical, and biological properties were measured. The results showed that, with increasing grazing intensities, the concentrations of total nitrogen, available nitrogen, organic matter, available phosphorus, available potassium, urease, catalase, and alkaline phosphatase in the soil decreased significantly with LG being mostly the greatest (P

Soil phosphorus (P) fractions and runoff P concentration were measured to understand the fate of soil P entering surface runoff water during summer cropping season of different double cropping systems under two fertilizer regimes. The dominant form of runoff P was particulate P (PP). Runoff total P (TP) was higher at the vegetative growth stage and lower at the crop reproductive stage. TP and PP were derived mainly from soil Olsen-P, Al-P and Fe-P and amounts increased with sediment content in runoff water. Runoff P discharge was closely related to the changes in soil P forms. Soil Olsen-P, mainly consisting of some Ca2-P and Al-P, was increased by elevating fertilizer rate. Along with crop growth, there were active interconversions among Olsen-P, Org-P, Fe-P and O-Al-P in the soil, and some available P converted into Ca10-P, with O-Fe-P possibly being a transitional form for this conversion. The oilseed rape/corn system had less runoff TP at the early stage, and wheat/sweet potato system had a lower runoff P at the late stage. Intercropping corn with sweet potato in the field with oilseed rape as a previous crop may be helpful for alleviating runoff P load during the summer in this region.

The vegetative growth and turion formation of Potamogeton crispus, a submersed aquatic macrophyte, was investigated under a range of phosphorus (P) concentrations (0.025, 0.25, 2.5 and 25 mg P L−1) in the ambient water free of algae, aiming to identify the responses of submersed aquatic macrophytes to nutrient enrichment, a common eutrophication problem in China and worldwide. Plant growth was not affected by different P concentrations in terms of biomass accumulation of stems and leaves. However, the contents of chlorophyll a and starch in plants decreased with increasing water P levels, whereas chlorophyll b and carotenoids declined with P level ranging from 0.025 to 2.5 mg P L−1. The soluble sugar content decreased when water P concentration increased up to 2.5 mg L−1. The P content in plants increased with increasing water P levels, whereas plant N content decreased and soluble protein increased when water P concentration increased over 0.25 mg L−1, implying that P. crispus may have modified its metabolism to adapt to water P availability. When P concentration increased to 25 mg L−1, the number and dry matter production of turions per plant decreased significantly. Meanwhile, there was a significant reduction in turion weight and the accumulations of soluble sugar and starch in turion, when water P concentration was over 0.25 mg L−1. The results suggest that turion formation in P. crispus is sensitive to P concentration in the ambient water, and high P levels may lead to decreases in P. crispus populations due to the decline in turion production.

The significantly lower annual rainfall experienced in Australia over the past decade together with projections of long-term climate change has placed increased emphasis on the use of pasture plants with superior tolerance to environmental stress, particularly drought, to ensure persistence for the grazing industries. Summer dormancy is one of the more important traits that grasses have to adapt to environments where there is little, variable, or no summer rainfall. In this article, the role that the summer dormancy trait has played in enhancing the survival of temperate perennial grasses in Australia is reviewed with special reference to orchardgrass (cocksfoot; Dactylis glomerata L.) and tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]. The performance of cultivars and populations with this trait is assessed in comparison to germplasm without the trait. Other major factors such as the contribution of rooting depth to stress tolerance and their possible relationship with summer dormancy are documented and evaluated. Current knowledge of the physiological basis by which summer dormancy improves survival of summer drought is also summarized.

Grasslands and rangelands occupy over 70% of the earth’s land area (Holechek et al., 2004; World Resource Institute, 2000), and are a major source of meat, milk and fibre production in the world. The rising demand for meat and milk in the past 30 – 40 years and the adverse impact from climate varibility have placed great pressure on the productive and sustainable use of grazing lands (Delgado, 2005; Nie & Norton, 2009). By 2020, it is predicted that developing countries will consume 72 m tons more meat and 152 m tons more milk compared to 2002/03 whereas developed countries’ increases will be 9 and 18 m tons for meat and milk, respectively (Delgado, 2005). Australia is the world’s driest inhabited continent. Half of its total land area has an average annual rainfall (AAR) of less than 300 mm. Around 60% is used for agriculture, of which over 90% is used for grazing (Peeters, 2008). A particular feature of the continent is the high rainfall variability which makes selecting the right pasture species/cultivars, optimising pasture and grazing management and avoiding overgrazing very challenging. About 5% of Australia’s grazing lands have been sown to introduced plant species and these improved pastures support a large proportion of the domestic livestock. The improved pasture species are productive and generally have high nutritive characteristics; however, their persistence is often poor due to the limited capacity to sustain a suite of varying soil, climatic and management conditions. A pasture survey in south west Victoria revealed that the majority of pastures were dominated by low-producing, ‘unimproved’ grass species (Quigley et al., 1992), and similar results were found in southern New South Wales (NSW; Virgona & Hildebrand, 2007). The main perennial pasture grasses sown in southern Australia are perennial ryegrass (Lolium perenne), phalaris (Phalaris aquatica), tall fescue (Festuca arundinaceum syn. Lolium arundinaceum), and cocksfoot (Dactylis glomerata) (Reed, 1996). These grasses differ in their requirements of rainfall, temperature and soil type and fertility for growth, therefore have a varying degree of adaptation in different regions. Plant breeders have developed new cultivars to improve one or more attributes for each of the grasses. Agronomists working with other specialists such as animal and soil scientists have developed management systems to accommodate the expression of the attributes from the new cultivars. At present there are large variations between cultivars within each species, not to mention between species.

A single functional leaf is usually sampled to evaluate the growth and photosynthetic assimilation of crops. However, there is large variation between leaves in winter oilseed rape (Brassica napus L.) at seedling stage. In this study, the morphological and physiological characteristics of various functional leaves were compared with characteristics of the whole plant at seedling stage for 2 years by using the oilseed rape cultivars Huaza 9 and Huaza 62 as plant material. The aim of this study was to identify a leaf that can represent the whole plant for assimilate accumulation characteristics at the seedling stage of the crop. The results showed that the photosynthetic rate and the contents of non-structural carbohydrates, nutrients and soluble proteins in fourth and fifth leaf of a plant were most closely related to those of the whole plant. The area and dry matter (DM) of all functional leaves were well correlated with those of whole plant, with the fifth leaf having the highest correlations. It is therefore recommended that the fifth leaf is most suitable to represent the whole plant for evaluation of growth and assimilate accumulation for winter oilseed rape at the seedling stage. The following regression equations for whole plant (y) and fifth leaf (x, dry matter or length × width) can be used to predict (1) DM accumulation (g) and (2) total leaf area (cm2) of the whole plant: (1) y = 3.32x + 1.51 (R2 = 0.88, P