Crop Physiology

In this chapter, we review the physiology of switchgrass from seed dormancy till the effects of water and nutrients stress on grown plants. These characteristics are presented and discussed mainly at the canopy and whole-plant level with emphasis on the agro-physiology of the species in view of the possible contribution of crop physiology to agricultural development. Switchgrass is noted for the variable degrees of seed dormancy regulated by endogenous and exogenous factors that determine the successful seedling establishment. Plant growth rates are determined by temperature while the reproductive phase is controlled mainly by photoperiod. There is also evidence that some physiological attributes, such as photosynthesis, transpiration, and water use efficiency differ between tetraploid, hexaploid and octaploid ecotypes. But despite these differences, in general switchgrass combines important attributes of efficient use of nutrients and water with high yields thanks to its ability to acquire resources from extended soil volumes, especially at deep layers. Moreover at canopy level, resources capture and conservation are determined by morpho-physiological characteristics (C{sub 4} photosynthetic pathway, stomatal control of transpiration, high leaf area index, low light extinction coefficient) that enhance radiation use efficiency and reduce carbon losses. However, specific information on switchgrass physiology is still missing, in particular deeper understanding of physiological principles controlling the water and nutrients acquisition mechanisms and allocation under suboptimal growing conditions. The physiology of tillering and root respiration are also factors that need further investigation