Due to the drastic reduction in the stratospheric ozone layer over the last two decades, investigations on the potentially destructive and inhibitory effects of UV-B radiation on plants have received ever greater attention. It must not be forgotten that the level of UV-B radiation at various points on the Earth's surface is rising not only due to the thinning of the ozone layer, but is also influenced by global climate change, the magnitude of cloud cover and snow cover, the quantity of pollutants in the atmosphere and the use of aerosols. From the point of view of world food supplies it is important to know how crops are capable of coping with the joint effect of factors causing climate change (CO2 content, temperature, rainfall, ozone) and the increase in UV-B radiation under growth conditions, especially in the regions where UV-B radiation has increased to the greatest extent over the last decade, such as South America, South East Asia, Australia, and even in the United States. Over the last twenty years the greatest quantity of information on the sensitivity of plants to UV-B radiation and on their defence mechanisms has been provided by experiments carried out in greenhouses and phytotron chambers. Although these experiments are of assistance in understanding the changes and phenomena observed in natural systems and under farm conditions, they only allow limited conclusions to be drawn on the actual effects of UV-B in the field, since a number of examinations have indicated that at the ecosystem level the effect of UV-B radiation is not necessarily inhibitory or damaging, but has more of a regulatory nature. Under field conditions the physiological processes of the crops are influenced by many simultaneous environmental factors, which may make the plants either more resistant or more sensitive to possible changes in the UV-B radiation level. In perennial plants the effects of UV-B may accumulate. An important consideration is the ability of genotypes in natural and artificial systems to keep up with rapid changes in the UV-B radiation level or in other environmental factors. The results of tests over the last twenty years indicate that the most frequent effect of UV-B in plants is an increase in the quantity of pigments that filter UV-B and the evolution of a pigment composition characteristic of the species, which may provide efficient protection to sensitive plant organs. This form of defence can be rapidly activated and covers a wide range, but varies from one species to another, so the damaging effect of UV-B on the growth, photosynthetic processes and photosynthetic pigment concentrations of plants cannot always be unequivocally demonstrated. In recent years investigations have concentrated mainly on crops grown in potentially endangered regions (rice, soya, wheat) in order to select the genotypes most resistant to UV-B radiation (and to other environmental factors). This could be critical for world food supplies. The results achieved so far suggest that a knowledge of the changes that can be expected at various trophic levels and in the relationships between these levels is essential for understanding the possible effects of UV-B radiation on agricultural crops. At present it can be said that in the northern temperate zone it is not an increase in the level of UV-B radiation that has the greatest effect on crop productivity, but the existence of other environmental limitations (e.g. drought, nutrient deficiency, etc.), which, however, influence the response of crops to UV-B radiation.
|Number of pages||20|
|Publication status||Published - Dec 1 2005|
ASJC Scopus subject areas
- Agronomy and Crop Science