Abstract

In the present investigation, the major chemical constituents in leaf and stem of alfalfa (Medicago sativa L.) cv Elena at three different stages of maturity were studied. The experiment was designed as a randomized block replicated three times. During growth and development, crude protein content decreased and cell wall constituents (Neutral Detergent Fiber-NDF, Acid Detergent Fiber-ADF and ADL- Acid Detergent Lignin) increased in both plant anatomical fraction of alfalfa. Lignin is a poorly characterized polymer and its exact properties vary depending on both the species of the plant and its location within the plant. Three stages of maturity taken from alfalfa leaf and stem were examined. The investigation was concentrated on the determination of chemical changes in the lignin during growth and development by the Attenuated Total Reflectance-Furior Transform Infrared (ATR-FTIR) spectrometric technique. The predominant component of lignin from alfalfa leaf was guaiacyl-type lignin. Despite the leaf, the predominant component of lignin from alfalfa stem was guaiacyl-syringyl-type lignin. A comparison between the signals from lignin in different development stages revealed the appearance of new peaks, which are indications of new bonds and changes in the structure of the lignin.

Key words: Alfalfa, cell-wall, lignin, attenuated total reflectance-furior transform infrared (ATR-FTIR) spectroscopy.