الفهرس 
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Abstract
Family Salicaceae (Salicales) is among the primitive woody dicotyledons. It represented in Egypt by two genera {Populus and Salix). During the last decades woody species of the Egyptian flora are exposed to human overexploitation. In addition to, the scarcity of rainfall and lack of species control. Accordingly this work was focused on the status of family salicaceae in Egypt.
this study aimed to: 1- clarify the distribution of Salix and Populus in Egypt. 2- revise the taxonomic status of the wild Salicaceae , 3- identify the factors controlling the species distribution. 4- inter-lecific1 affinities between Salix species will be studied based on pollen grain isozymes and Random Amplification Polymorphic DNA (RAPD)., with a special reference to sex separation and the problem of seed formation in Egypt.
This work based on both of field study where specimens were collected from 46 localities and Egyptian herbaria. The fresh and herbarium specimens were subjected to taxonomic revision according to morphological characters. The morphological characters including plant height, length and width of leaf blade, length of leaf petiole, in addition to the catkines, female and male flowers characteristics. Soil supporting the studied localities was collected from the tree rhizosphere at 20 - 40 cm. Climatic data in the investigated sites are cited based on meteorological authority data.
Pollen grains of the Salix species under investigation were prepared for scanning electron and examined by a JOEL JSM 5400 LV SEM microscope. Isozyme study was carried out on juvenile Salix leaves, esterase(EST), glutamate oxalo-acetate transaminase (GOT), and peroxidase (PRX). RAPD analysis was carried out on male and female Salix specimens collected from varied localities. DNA samples were extracted from 50 mg of juvenile leaf tissues in each sample. The amplification was done with random synthetic-16-oligonucleotide primers of 10 bases.
The taxonomic revision revealed that genus Salix in Egypt represented by two wild species (S. mucronata Thunb. and S. tetrasperma Roxb.). Female S. mucronata trees were distributed along Nile valley and delta and extended eastward to Ismailia. While, a few male S. mucronata trees were traced only in Fayium region. While, S. tetrasperma was traced only as male trees; female trees never traced in Egypt.
Salix mucronata can be distinguished morphologically from S. tetrasperma as follows: leaves of S. mucronata not exceeding 3.5 cm diameter, while S, tetrasperma leaves generally more than 6.0 cm diameter. Male inflorescence of S. tetrasperma is up to 11 cm long, while that of S. mucronata not exceeding 4.5 cm long. Similarly female inflorescence of S. tetrasperma is up to 12 cm long while that of S. mucronata not exceeding 3.0 cm long.
Salix species is colonizing the floodpiain, along the irrigation canals of the Nile valley. It grows quickly, produces a massive root system. The results demonstrated that most Salix species collected from soils of moderate soil texture where moisture content and soil texture are the most important factors affecting Salix growth.
The present study showed that temperature is a limiting factor for S. tetrasperma. It grows in a habitat characterized by low temperature in lower Egypt and absent from Upper Egypt of high temperature.
The SEM investigations carried out on two Salix species, revealed a tricolpate, reticulate elliptical pollen grains. Pollen of S. tetrasperma has a smaller size (E x P: 13.33 x 15.50 µm) and granulate lumen sculpture. While, S. mucronata possesses a larger grain size (ExP: 11.51 x 19.31µm) and psilolumina lumen sculpture.
The developed zymograms demonstreted the presence of sex differential and sex - linked bands in case of esterase and peroxidase isozymes, Accordingly, esterase and peroxidase enzymes can be used to prove sex identification. The retrieved isozyme results also reflected a correlation between the concentration of isozyme bands with soil pH and EC.
Within the studied male and female Salix genotypes in this study, there are RAPD bands appeared to be sex-related DNA bands; similarly as retrieved from isozyme study. Accordingly, RAPD technique also can be used to prove sex identificatjbn of Salix species.
populus euphratica Oliv. is the third wild species of family Salicaceae in Egypt. The species traced as female tree endemic to Siwa Oasis. The area characterized by very low rainfall, high evaporation, high summer temperature, in addition to high soil salinity
Sex segregation is the common phenomenon observed in wild salicaceae grow in Egypt; seeds not formed in these species. P. euphratica naturalized as female tree only; Salix tetrasperma was represented as male trees only. Despite of Salix mucronata dominant as female trees while male trees traced in Fayium region, the plant also, never forming seeds in this area. This may be attributed to absence of pollinator vector.
Based on the above species features, Salicaceae is an endangered family In Egypt. All the species are characterized by critically low breeding capacity and lack of genetic diversity. In addition to human overexploitation of these wood trees. Accordingly Salicaceae in Egypt treated as endangered species; germplasm collection, conservation and propagation protocols must be addressed to these species for its future sustainability.