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Embryological observations on unpollinated ovary culture of mulberry [Morus alba L.]

100%

Thomas T. D.

tom 46

87-94

A three-step procedure was adopted for the induction of gynogenesis in two cultivars of mulberry (Morus alba L.). This includes in vitro flowering, inflorescence segment culture and isolated ovary culture. In the third step, that is, isolated ovary culture, the cultured ovaries burst and an embryo emerged from the ovary. The present paper investigates the ontogeny of the developing gynogenic embryo. The study confirmed that the gynogenic embryo emerged from the egg cell. Before the onset of division of the egg, all other cells of the embryo sac degenerated in the majority of ovules, but in exceptional cases the polar nuclei will be retained along with the dividing egg cell. The presence of the gynogenic embryo along with free-nuclear autonomous endosperm is the most important feature of the present investigation. Autonomous endosperm is formed from either the polar nuclei or secondary nucleus. In both cultivars used for the experiment, the percentage of ovaries showing proembryo induction during inflorescence segment culture is much higher than that of ovaries producing gynogenic plants during isolated ovary culture. This suggests the degeneration of some gynogenic embryos during the initial stages of induction.

Pulvinus: an ideal explant for plant regeneration in Caesalpinia bonduc (L.) Roxb., an important ethnomedicinal woody climber

51%

Cheruvathur M. K. , Britto J. , Thomas T. D.

nr 2

This study demonstrates the morphogenic potential of pulvinus, an important organ situated at the base of the petiole or rachis of leguminous plants. Plant regeneration via pulvinus-derived calli of Caesalpinia bonduc has been achieved. Organogenic calli have been derived from the explant 45 days after culture on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) alone or in combination with 6-benzylaminopurine (BA). Optimum callus induction (100%) occurred when the pulvini were cultured on MS medium fortified with 6 mg l⁻¹ 2,4-D and 1 mg l⁻¹ BA. The highest shoot induction was obtained when the calli were transferred to MS medium supplemented with 5 mg l⁻¹ BA and 1 mg l⁻¹ indole-3-acetic acid (IAA). On this medium, 87% cultures responded with an average number of 4.2 shoots per culture. The maximum root induction from the regenerated shoots was observed on half strength MS medium containing 6 mg l⁻¹ indole-3-butyric acid (IBA). Here 100% shoots rooted with a mean number of 6.3 roots per shoot. The regenerated plantlets were acclimatized and subsequently showed normal growth. This efficient protocol will be helpful for propagating elite clones on a mass scale and could be utilized for genetic transformation study.