Presentation Title

Brassinolide promotes shoot formation and inhibits protocorm hair development in the orchid Spathoglottis plicata

Start Date

November 2016

End Date

November 2016

Location

HUB 302-#61

Type of Presentation

Poster

Abstract

Brassinosteroids typically stimulate cell division and elongation, among many other plant growth promoting responses. While the role of brassinolide in other plant systems has been well studied, the effects of this hormone on early orchid development have not been characterized. Moreover, a few studies have looked at the interactive role of brassinolide and auxin in plant development, with an emphasis on lateral root initiation and root geotropisms, but this type of work has not been conducted on orchids. Embryos of orchid seed lack primordial shoots and roots, and during early germination, they form a group of undifferentiated cells, or a protocorm from which a meristem and first leaf will form. Hairs typically begin to develop on the protocorm at two to three weeks. Since root initiation is delayed six weeks post germination, this system allowed us to record the effects of this hormone on shoots alone. For this work, orchid seeds were sown on standard culture media until 10 days, and then subcultured onto media containing brassinolide, brassinozole (an inhibitor of brassinolide biosynthesis), auxin (2-4D), BBO (an inhibitor of auxin biosynthesis), TIBA (a polar auxin transport inhibitor), or a combination of these. Their growth responses were evaluated after an additional 14 days in culture. Data was collected on leaf length/width, protocorm diameter/length, percentage of seedlings with a first leaf, and percentage of seedlings with protocorm hairs. As expected, brassinolide caused stem/protocorm elongation, while auxin stimulated the formation of hair-producing callus tissue from the protocorm and TIBA inhibited leaf formation. Additional results included the restoration of leaf growth in the TIBA-treated seedlings and 2,4-D seedlings with the addition of brassinolide. Also, the brassinozole promoted hair initiation. These findings suggest that similar to root responses, brassinolide affects the direction of auxin flow and ultimately impacts shoot and hair formation in seedlings.

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Brassinolide promotes shoot formation and inhibits protocorm hair development in the orchid Spathoglottis plicata

HUB 302-#61

Brassinosteroids typically stimulate cell division and elongation, among many other plant growth promoting responses. While the role of brassinolide in other plant systems has been well studied, the effects of this hormone on early orchid development have not been characterized. Moreover, a few studies have looked at the interactive role of brassinolide and auxin in plant development, with an emphasis on lateral root initiation and root geotropisms, but this type of work has not been conducted on orchids. Embryos of orchid seed lack primordial shoots and roots, and during early germination, they form a group of undifferentiated cells, or a protocorm from which a meristem and first leaf will form. Hairs typically begin to develop on the protocorm at two to three weeks. Since root initiation is delayed six weeks post germination, this system allowed us to record the effects of this hormone on shoots alone. For this work, orchid seeds were sown on standard culture media until 10 days, and then subcultured onto media containing brassinolide, brassinozole (an inhibitor of brassinolide biosynthesis), auxin (2-4D), BBO (an inhibitor of auxin biosynthesis), TIBA (a polar auxin transport inhibitor), or a combination of these. Their growth responses were evaluated after an additional 14 days in culture. Data was collected on leaf length/width, protocorm diameter/length, percentage of seedlings with a first leaf, and percentage of seedlings with protocorm hairs. As expected, brassinolide caused stem/protocorm elongation, while auxin stimulated the formation of hair-producing callus tissue from the protocorm and TIBA inhibited leaf formation. Additional results included the restoration of leaf growth in the TIBA-treated seedlings and 2,4-D seedlings with the addition of brassinolide. Also, the brassinozole promoted hair initiation. These findings suggest that similar to root responses, brassinolide affects the direction of auxin flow and ultimately impacts shoot and hair formation in seedlings.