Abiotic stresses are one of the major constraints to crop production and food security worldwide. The situation has aggravated due to the drastic and rapid changes in global climate. Heat and drought are undoubtedly the two most important stresses having huge impact on growth and productivity of the crops. It is very important to understand the physiological, biochemical, and ecological interventions related to these stresses for better management. A wide range of plant responses to these stresses could be generalized into morphological, physiological, and biochemical responses. Interestingly, this review provides a detailed account of plant responses to heat and drought stresses with special focus on highlighting the commonalities and differences. Crop growth and yields are negatively affected by sub-optimal water supply and abnormal temperatures due to physical damages, physiological disruptions, and biochemical changes. Both these stresses have multi-lateral impacts and therefore, complex in mechanistic action. A better understanding of plant responses to these stresses has pragmatic implication for remedies and management. A comprehensive account of conventional as well as modern approaches to deal with heat and drought stresses have also been presented here. A side-by-side critical discussion on salient responses and management strategies for these two important abiotic stresses provides a unique insight into the phenomena. A holistic approach taking into account the different management options to deal with heat and drought stress simultaneously could be a win-win approach in future.

Summary1. Acacia nilotica is a spinescent woody legume that has become highly invasive in several parts of the world, including Australia where it has been declared a weed of national significance. Understanding the likely potential distribution of this notorious plant under current and future climate scenarios will enable policy makers and land managers to prepare appropriate strategies to manage the invasion. 2. CLIMEX was used to synthesize available information from diverse sources to model the invasion potential of A. nilotica and gain insights into the climatic factors limiting its range expansion. The model identified areas at risk of further invasion so that early preventative or ameliorative measures could be undertaken in a timely manner. 3. The potential distribution of A. nilotica in Australia under current climatic conditions is vast, and far greater than the current distribution. 4. Global climate change is likely to increase markedly the potential distribution of A. nilotica in Australia, significantly increasing the area at risk of invasion. The factors of most importance are the expected increases in water-use efficiency of A. nilotica due to increased atmospheric CO 2 concentrations, allowing it to invade more xeric sites further inland, and increased temperatures, allowing it to complete its reproductive life cycle further southward (poleward). Synthesis and applications.Simple paddock quarantine procedures may provide a means of limiting the range of A. nilotica within its potential distribution under current, as well as future, climate scenarios. The projected increased growth potential of A . nilotica throughout its current range suggests that if future management patterns result in seed pods lying unconsumed on the ground, heightened vigilance may be required to identify and eradicate new invasion foci arising from flood dispersal. The increased growth potential may also result in an alteration of the economic balance, in favour of harvesting A. nilotica for agroforestry or local bioenergy projects. A crucial component in containing this invasion will be raising public awareness of the invasion threat posed by A. nilotica , its identification and suitable control techniques.

Grass weed populations resistant to aryloxyphenoxypropionate (APP) and cyclohexanedione herbicides that inhibit acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) represent a major problem for sustainable agriculture. We investigated the molecular basis of resistance to ACCase-inhibiting herbicides for nine wild oat (Avena sterilis ssp. ludoviciana Durieu) populations from the northern grain-growing region of Australia. Five amino acid substitutions in plastid ACCase were correlated with herbicide resistance: Ile-1,781-Leu, Trp-1,999-Cys, Trp-2,027-Cys, Ile-2,041-Asn, and Asp-2,078-Gly (numbered according to the Alopecurus myosuroides plastid ACCase). An allele-specific PCR test was designed to determine the prevalence of these five mutations in wild oat populations suspected of harboring ACCase-related resistance with the result that, in most but not all cases, plant resistance was correlated with one (and only one) of the five mutations. We then showed, using a yeast gene-replacement system, that these single-site mutations also confer herbicide resistance to wheat plastid ACCase: Ile-1,781-Leu and Asp-2,078-Gly confer resistance to APPs and cyclohexanediones, Trp-2,027-Cys and Ile-2,041-Asn confer resistance to APPs, and Trp-1,999-Cys confers resistance only to fenoxaprop. These mutations are very likely to confer resistance to any grass weed species under selection imposed by the extensive agricultural use of the herbicides.aryloxyphenoxypropionate ͉ Avena ͉ cyclohexanedione

Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening natural ecosystems and agroecosystems in over 30 countries worldwide. Parthenium weed causes losses of crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and resulting in serious economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (namely cultural, mechanical, chemical and biological control) have been used to minimise losses caused by this weed, but most of these approaches are ineffective and uneconomical and/or have limitations. Although chemical control using herbicides and biological control utilising exotic insects and pathogens have been found to contribute to the management of the weed, the weed nevertheless remains a significant problem. An integrated management approach is proposed here for the effective management of parthenium weed on a sustainable basis.