Climate changes the major highlighted issue in the world. Pakistan being a developing country and its agriculture affected badly by the unsteady climate. Dynamic climate temperature playing a key role in poignant agriculture and plant production.
By Anam Saira, Samina Tanveer
The extent to increase in temperature and the potential of more extreme events associated with climate change making the agricultural productivity at a risk. Although, all the crops being cultivated comparatively sensitive to this activity but Maize among the most important crops being sensitive and its productivity reduced to a greater extent. The Maize enjoying an outsized role in the gross domestic product comes at third place in production after wheat and rice in Pakistan growing on a large area with the majority of farmers adapting to cultivate maize. In Pakistan maize planted doubly a year with two growing seasons mainly the summer and spring.
“Climate change increase in carbon dioxide emissions in the coming decades, the global average temperature will rise between 4 and 6 degrees Celsius, with a near doubling of atmospheric CO2 by century’s end. Those hotter, CO2-rich future conditions are akin to turning up the heat and pumping CO2 into a greenhouse. The likely result, assuming no other limiting factors such as lack of nutrients, is an explosion of plant life”.
Temperature and Heat Sensitivity:
Maize being a temperature and droughty sensitive crop badly affected by temperature rise in both the seasons but the major damage cause in spring season which suddenly rises in temperature after mid of March affects crop productivity. Warmer temperature affects the maize productivity directly generally in two ways. Higher temperature increases the crop growth rates by shortening their life-span through the process of bolting. This ends up in less and reduced time period crop to grain development affecting the crop yield potential.
The tasseling and pollination stage both affects equally by rise in temperature as the temperature increased the male pollen become sterile due to excessive water loss and the accumulation of assimilates produced as a result of photosynthesis reduced. Fertilization in maize occur when the pollen fallen from the tassel of the maize plant received by the silk. Increased temperature above 32C greatly reduce the ability of the pollen to attach to the silk and the occurrence of silk on the cob also delayed which reduce the period of co-occurrence of both the pollen and the cob. The increase air temperature also affects the maize pollen to become sterile and non-sticky to the cob because of the loss of water from the pollen during its flight. Pollen desiccated to 20% of its original water content is still capable of germination. The reduction in pollen water content under heat stress is unlikely to be the main reason of reduced pollen viability. The location of the tassel on the maize plant also provides maximum exposure to extreme temperatures increasing the probability of pollen damage as a result of heat stress.
Reduced Plant Cycle:
The overall reduced period of plant lifecycle adversely affects the interception of solar-radiations results in less production of photosynthates resulting in production of smaller cobs with lesser and smaller number of grains. The lesser and smaller number of grain production mainly due to the lesser amount of starch production for the grain filling of maize and incomplete or sterile pollens which results in crinkled seeds having only the seed coat with no or lesser weight reducing the overall production. On kernel development and final kernel mass due to a reduction in the number or size of endosperm cells formed thereby reducing sink capacity of maize cob. During this stage heat stress affects cell division, sugar metabolism, and starch biosynthesis, reducing subsequent dry matter accumulation within kernels. The time duration of the grain filling process (35 days) is the longest physiological process during the reproductive stage, increasing the probability of experiencing high temperature during this stage.
Heat stress during grain filling reduces endosperm starch content, the primary constituent of kernels. Maize kernel weight is the product of the rate and duration of grain filling, both of which are affected by temperature. High temperature during this period is associated with a reduction in the duration of grain filling. On an average 7% yield decline occur in maize per day when the temperature increased during the tasseling stage. In maize productivity is the count of number and weight of seeds per cob the lesser the number of seeds less production and hence poor yield.
Mitigation of Climate Change:
The solution to these problems lies with in the development of such new varieties which not only have the capability to cope with heat and drought stresses but also have a shorter life span to mitigate the heat stress with no effect on yield. On the basis of management, it can be mitigated using application of nitrogen and magnesium which helps to reduce the effect of heat stress in maize plant. Light but frequent irrigation may help to reduce the effect of heat on the maize plant. There should be a variety development program that not only emphasizes on yield of the crop but also addresses the problems related to the changing climate and the challenges related to it.
Farmer should also emphasize on the new technology to improve its per acre yield by becoming not reluctant in adopting wise and safe agriculture and clean environment which has a lesser impact on the environment. New agricultural practices will not only have to prevent heat stress but also improve the resilience of the system while reducing production costs. The government should conduct such programs that not only make agriculture friendly to the environment but a check balance should be created to check and forecast the climate change strategy and the crop planting time should be forecasted to the farmers which help them to mitigate such problems associated with the changing and damaging climate to the crop productivity.
Authors : Anam Saira, Samina Tanveer Department of Botany, University of Agriculture Faisalabad.