MICROMORPHOLOGICAL OBSERVATION OF EUCALYPTUS SEEDS, MULTIVARIATE STATISTICAL ANALYSES AND MODELING OF THEIR GERMINATION UNDER SALT STRESS AND OSMOTIC CONSTRAINT
ABSTRACT Micromorphological characters including surface, length and width of seeds were recorded for 19 species of Eucalyptus (Myrtaceae) using stereomicroscope to determine the importance of seed morphological characters as an additional tool for identification.With the aim of selecting and valorizing abiotic-stress-tolerant species with landscape and industrial values and would be a potential solution for valorizing dry arid area and development of land degradation, we launched the assessment of the performance of five Eucalyptus species (E. torquata, E. sargenti, E. gillii, E. gomphocephala x E. cornuta and E. microtheca) under salinity and osmotic potential constraints. Several NaCl concentrations (0, 3, 6, 9, 12, and 15 g.L-1) and several osmotic potentials (0, -0.03, -0.1, -0.7, -1 and -1.6 MPa) were applied to seeds cultivated in petri dishes for a period of one month. Germination rates, means time of germination and coefficent of velocity were evaluated to better understand the salt stress and osmotic potential effect on germination. Univariate and multivariate analyses were used to identify the major characteristics pertaining to salinity tolerance. Modeling of germination under both constraints saline and osmotic stress is carried out to predict the behavior of the species. The hybrid E. gomphocephala x E. cornuta was more tolerant to salt stress (15 % at 12 g.L-1) and osmotic potential (61 % at -1.6 MPa) than the others species of Eucalyptus; it showed a higher germination percentage under all tested potentials, when compared to the not hybrid species of Eucalyptus. Our analyses of seeds morphology revealed that the observations shown diversity of morphological characters in seeds. Area, length and width of seeds vary significantly between species of Eucalyptus. Micromorphological characters can provide basis for classification and delimitation of genus Eucalyptus.