Sané D, Aberlenc-Bertossi F, Gassama-Dia Y K, Sagna M, Trouslot M F, Duval Y, Borgel A
Laboratoire de Biotechnologies Végétales, Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, BP 5005, Sénégal.
Ann Bot. 2006 Aug;98(2):301-8. doi: 10.1093/aob/mcl104. Epub 2006 Jun 1.
The date palm is a dioecious perennial species of the Arecaceae for which in vitro micropropagation is essential to ensure the renewal of palm plantations. This study presents a histocytological analysis of the traditional Mauritanian Amsekhsi cultivar beginning from the initial callogenesis and continuing up to the establishment of the cellular embryogenic cell suspensions. The formation of somatic embryos and their development into rooted plants are also described.
Foliar segments of seedlings cultured in the presence of 2,4-D produced primary calli that were chopped to produce fine friable granular calli that subsequently produced cellular suspensions when transferred to liquid medium. The somatic proembryos that developed after removal of the 2,4-D were plated on agar medium where they developed into rooted plants. Thin sections of tissue fragments taken at each stage of the process were stained using Periodic Acid Schiff and Naphthol Blue-Black.
The first cellular divisions were localized close to the vascular vessels of the leaf. The primary calli were obtained within 2 months. Fine friable granular calli grew quickly after the primary calli were chopped. Individual embryogenic cells were identified that rapidly started to divide and developed into globular proembryos. In addition, in the microcalli, breaking zones appeared in the thick pectocellulosic walls which delimited the pluricellular proembryos. The anatomy of somatic embryos is similar to that of zygotic embryos despite a deficit in the accumulation of intracellular proteins. When rooted with NAA, the vitroplants developed a strong orthotropic taproot.
This study contributes to understanding the whole process of somatic embryogenesis, but two specific questions remain to be answered: what factors are involved in the reactivation of the somatic cells at the beginning of the initial callogenesis, and why do the somatic embryos not accumulate proteins in their tissues during maturation?
海枣是棕榈科的一种雌雄异株多年生植物，其离体微繁殖对于确保棕榈种植园的更新至关重要。本研究对传统的毛里塔尼亚阿姆塞克西品种进行了组织细胞学分析，从最初的愈伤组织形成开始，一直持续到细胞胚性细胞悬浮系的建立。还描述了体细胞胚的形成及其发育成生根植株的过程。
在2,4 - D存在的情况下培养的幼苗叶片切段产生了初级愈伤组织，将其切碎以产生细小易碎的颗粒状愈伤组织，随后转移到液体培养基中时产生细胞悬浮系。去除2,4 - D后发育的体细胞原胚接种在琼脂培养基上，在那里它们发育成生根植株。在该过程的每个阶段采集的组织片段薄片用高碘酸希夫试剂和萘酚蓝黑染色。
最初的细胞分裂位于叶片的维管束附近。2个月内获得了初级愈伤组织。初级愈伤组织切碎后，细小易碎的颗粒状愈伤组织迅速生长。鉴定出单个胚性细胞，它们迅速开始分裂并发育成球形原胚。此外，在微愈伤组织中，界定多细胞原胚的厚果胶纤维素壁上出现了断裂区。尽管体细胞胚细胞内蛋白质积累不足，但其解剖结构与合子胚相似。用萘乙酸生根后，离体植株发育出强壮的直根系主根。
本研究有助于理解体细胞胚胎发生的全过程，但仍有两个具体问题有待解答：在最初的愈伤组织形成开始时，哪些因素参与了体细胞的重新激活，以及为什么体细胞胚在成熟过程中其组织中不积累蛋白质？
