WE ARE rushing through second decade of 21st century where problems are different and complex. Most of the intellectuals of the past indicated that human survival during this era will be a challenge. Present day social and economic issues of the world are justifying those alarming predictions. All the threatening forecasts are being realized in a very drastic manner. Focusing the trembling economies of modern world and devastating environmental regimes, it becomes painfully clear that humanity is at the verge of destruction. A huge portion of human population is devoid of basic needs like food, clothes and shelter. Every person with all his senses working properly can figure out that these needs are primarily based on agriculture. No matter where we are standing in economic race or modernization quest, the base is and will remain the agriculture directly or indirectly. Although both of its parts, animals and crops, are equally important but the widespread nature of crops make them worth considerable. Search and research on the crop production systems, cropping patterns, cropping rotations and land management has been done intensively. So many landmarks had been achieved by the great scientists who ensured the food security of the globe. However, the race between population and food production is now getting very serious as humans seem to be more concerned about exploiting the resources rather than improving the production lines.

Crop production is an important aspect of agriculture and the yield improvement is the prime task for scientific as well as farming communities. It has been long time since when people are focusing the domestic crops to improve their yield levels through number of management options. In a wider frame crop yields are dependent upon genetic factors, environmental factors and management factors. Environment change is very clear and anthropogenic activities of human race are the biggest cause for it. But as a matter of fact it is happening at a rate beyond all the predictions and cure efforts just playing havoc all around. Very minor contributions in terms to stop or reduce its damages are actually proving fruitful. On the other hand, a lot of restriction is present in the way to improve genetic makeup of crops. This particular aspect has been revolutionized previously through breeding efforts and recently through charismatic advances of biotechnology. This tier was most focused and due to these improvements we are still being fed. But such improvement and breakthroughs also have certain limitations and saturation points and may be at moment scientific community has reached that particular level. So now the responsibility to take charge and set the momentum is of managerial hierarchy. Each and every person involved in food production chain has to play a vital and significant role in this regard. Scientists have to explore options and managers and farmers have to validate and evaluate those thorough practicing at field. Besides all other options supreme slot is of crop growth promotion and crop protection.

Plants are living organisms and they have a variety of lively responses and actions. Whenever circumstances are not suitable for their growth and development they undergo certain adaptive mechanisms. They use to develop different morphological, physiological and biochemical strategies to make sure their survival. Being critical observers of nature many researchers may have noticed the thick cuticle, waxy leaf layers or sunken stomata of desert plants keeping them safe from hot weather. It is just one example how plants respond to changes in their environment. This particular response is morphological and quite visible but more interestingly there is wide range of very unique responses which are hidden often but exist and prevails in ecosystems. One of the most significant physiological cum biological responses is exudation of lethal chemicals into environments. A large number of plants release different types of chemicals in their surroundings under different environmental conditions. Plants produce some chemicals during different physiological processes like photosynthesis, respiration, translocation, and nutrient metabolism. Most of these chemicals are used directly or indirectly for structural formation and other functions but some of them are precursors of metabolic functions to be taken place at later stages. Some others are produced as if they have no visual use in plant body and scientifically they are known as secondary metabolites. These are actually poisons which may destruct the plant itself if retained inside the plant body so that plants have to get rid of these lethal chemicals. They use to release them from roots and aerial parts through exudation, volatilization, decomposition and leaching. In this form these are called allelochemicals. Anyways in more understanding way they can be said as phytoweapons. Yes, weapons! They can play great role in plant survival and performance.

Changing climate and vicious human activities are enhancing the occurrence of variety of stresses. Major environmental catastrophes are heat, cold, drought, salinity and waterlogging. These stresses impose negative effects on plants. Plants use to synthesize secondary metabolites in higher amounts as compared to normal conditions under stress. These chemicals help them to induce oxidative stress. Each and every stress in plant leads to a secondary stress which is oxidative stress. It is actually the production of Reactive Oxygen Species (ROS) which are harmful to plant parts but by the biosynthesis of secondary metabolites as an adaptive mechanism is triggered and signals are transducted across the plant body which efficiently acts to scavenge all the ROS by producing antioxidants. The whole mechanism is very crucial in plant defense and the pivotal role is played by these phytoweapons. In this way plants are well able to withstand and tolerate the unwanted changes in environment.

The similar trend is adopted by plats in case of living hazards and biotic stresses. They can easily overcome insect pests, diseases, rodents and predators. By using allelochemicals many insects are repelled by plants. It is well evident through scientific research that plants interact with algae, fungi and bacteria by releasing allelochemicals and offering resistant to their attacks. Nematodes and other problematic microorganisms are also controlled and resisted by plants through these potent chemicals. Many of the herbs and wild shrubs are even more resistant against different grazing animals and rodents because of high levels of allelochemicals production. Domestic crops, herbs and tress are very important part of agriculture. A varying degree of allelopathic potential has been observed in different crops and plants. Such plants have ability to release allelochemicals in root zone and atmosphere. In this way they are able to better compete with weeds because such chemicals drastically suppress the growth and vigor of other plants in vicinity. This particular fact is very encouraging and has been exploited for organic weed management in agro-ecosystems.

Plants release secondary metabolites/allelochemicals in their surroundings to ensure their survival naturally. These potent chemicals have stringent role in adaptive mechanisms and plant defense. Phytoweapons act naturally and the whole process is denoted as allelopathy but the very same process can be used against biotic as well as abiotic constraints to crop production as management tool. It is a bright approach to screen, isolate and evaluate such crops having this peculiar feature to assess their ability of tolerance/resistance against stresses. It is need of the hour to motivate scientific community to commence a comprehensive research program to screen, optimize and evaluate these useful chemicals through different means.

Agronomists have already taken the charge by initiating research towards finding allelopathic crops, allelopathic interactions prevailing in ecosystems and their role as potential defense molecules. Further emphasis is inevitable to integrate the multi disciplines for a complementary organization of subject knowledge and practical implication. Everyone has to realize his role and to take part in an efficient manner and of course sharing these facts is also very vital. So, I hope these lines have something to provoke awareness about the fact stated. In the long run it will help to sustain the agricultural production.

The writers are associated with the Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.

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