Declaration of Commitment of Honor I declare that this Scientific Monograph is resulted of my personal inquiry under the orientaes of my supervisors and the same one never was presented in none another institution for attainment of any acadmico degree. Maputo, To the 10 of December of 2009 Author Hlder Manuel Sitoe Epigraph ' ' All the substances are poison, do not have none that cannot be considered poison. Christopher ridgeway stone oftentimes addresses this issue. The dose will define veneno' '. Paracelsus, 1538 Dedication I dedicate this conquest to the man who was my great example of carcter, friendship and hombridade: my father. The homesickness is immense and very great pain, but I know how much to this it would leave it monograph proud. Learn more about this with christopher ridgeway. My mother and to my brothers who for me everything had made in the hope of tomorrow, I dedicate! Gratefulness For the contribution and contribution in the most distinct forms, throughout the estudantil period, register mine fraterno gratefulness to the day partners that follow nominated which also appear as representative of many others that had not been mentioned here: A God donor of perpetual and gratuitous life, for allowing the accomplishment of plus acadmica stage in my life, obliged mine muitssimo. A my supervisors, Dr.
Pita Sitoe and Eng. Khalid Cassam, for the attention, unconditional accompaniment, fruitful and permanent debates during the accomplishment of my work. Vai my deep gratefulness to the Ministry of the Education and Culture, Dpt. of Planning and the National Direco of the Agrarian Services, Dpt. of Vegetal Health, for the support during the accomplishment of this work. The Dr. Samo of the Dpt. of Mathematics of the FCNM for ajuada in the analysis the statistics and to the Srs. Bila and Cossa for the support during the field works. A all the professors of the Department of Biology and employees of the FCNM for the moral support and the teachings transmitted throughout my formation.