The genus Smilax Linnaeus, 1753 (Smilacaceae) is a large genus of dioecious plants distributed in tropical, subtropical and temperate regions. Some Smilax species have medicinal importance and their identification is important for the control of raw material used in the manufacture of phytotherapeutical products. The karyotypes of seven Brazilian Smilax species were investigated. Mitotic metaphases of roots from young plants were analysed in Feulgen-stained preparations. The karyotypes were asymmetric and modal with 2n = 2x = 32 chromosomes gradually decreasing in size. In S. goyazana A De Candolle & C De Candolle, 1878, a polyploid species, 2n = 4x = 64. In all the species, the large and medium-sized chromosomes were subtelocentric and submetacentric and the small chromosomes were submetacentric or metacentric. Their karyotypes were quite similar, with differences in the arm ratio of some chromosomes. S. fluminensis Steudel, 1841 differed from the other species by having a large metacentric chromosome 1. These findings suggest that evolution occurred without drastic changes in the chromosomal structure in the species analyzed. Terminal secondary constrictions were visualized on the short arm of some chromosomes, but they were detected only in one homologue of each pair. Due to the terminal location and the degree of chromosome condensation, secondary constrictions were not visualized in some species. The nucleolus organizer regions (NORs) were mapped by silver-staining and fluorescent in situ hybridization (FISH) in S. rufescens Grisebach, 1842 and S. fluminensis. Silver-staining and FISH signals were colocalized on the short arms of six chromosomes in S. rufescens and four chromosomes in S. fluminensis. In FISH preparations, one of the largest chromosomes had the secondary constrictions highly decondensed in some cells. This finding and the heteromorphism observed in Feulgen-stained chromosomes suggest that differential rRNA gene expression between homologous rDNA loci can occur in some cells, resulting in different degrees of ribosomal chromatin decondensation. The presence of a heteromorphic chromosome pair in S. rufescens, S. polyantha Grisebach, 1842 and S. goyazana suggests a chromosomal sex determination in these dioecious species.

中文翻译：

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1753种巴西S（Smilacaceae）的核型结构和NOR活性。

Smilax Linnaeus，1753（Smilacaceae）属是雌雄异株的大型属，分布在热带，亚热带和温带地区。一些S目具有药用重要性，其鉴定对于控制植物治疗产品生产中所用原料的控制很重要。研究了七个巴西S的核型。在Feulgen染色的制剂中分析了幼株根的有丝分裂中期。核型是不对称的和模态的，2n = 2x = 32条染色体的大小逐渐减小。在S. goyazana A De Candolle和C De Candolle（1878年）中，有一个多倍体物种，2n = 4x =64。在所有物种中，大中型染色体为亚远心和亚超中心，小染色体为亚近中心或超中心。它们的核型非常相似，但某些染色体的臂比不同。S. fluminensis Steudel，1841与其他物种的不同之处在于，它具有较大的亚中心染色体1。这些发现表明，在所分析的物种中，进化并未发生染色体结构的剧烈变化。在某些染色体的短臂上可以看到末端的次要收缩，但仅在每对的一个同源物中才检测到。由于末端位置和染色体浓缩程度，在某些物种中未发现次级缩窄。通过银染色和荧光原位杂交（FISH）在S. rufescens Grisebach，1842和S. fluminensis中绘制了核仁组织区（NORs）。银染和FISH信号共定位在rufescens中的6条染色体和fluminensis中的4条染色体的短臂上。在FISH制剂中，最大的染色体之一在某些细胞中具有高度缩合的次级缩窄。这一发现和在Feulgen染色的染色体中观察到的异质性表明，同源rDNA基因座之间的rRNA基因表达差异可能在某些细胞中发生，导致核糖体染色质的不同程度的缩聚。在S. rufescens，S。polyantha Grisebach，1842和S. goyazana中存在异型染色体对，表明这些雌雄异体物种的染色体性别决定。这一发现和在Feulgen染色的染色体中观察到的异质性表明，同源rDNA基因座之间的rRNA基因表达差异可能在某些细胞中发生，导致核糖体染色质的不同程度的缩聚。在S. rufescens，S。polyantha Grisebach，1842和S. goyazana中存在异型染色体对，表明这些雌雄异体物种的染色体性别决定。这一发现和在Feulgen染色的染色体中观察到的异质性表明，同源rDNA基因座之间的rRNA基因表达差异可能在某些细胞中发生，导致核糖体染色质的不同程度的缩聚。在S. rufescens，S。polyantha Grisebach，1842和S. goyazana中存在异型染色体对，表明这些雌雄异体物种的染色体性别决定。