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Title: GENERATIONAL DIFFERENCES IN RESPONSE TO DESICCATION STRESS IN THE DESERT MOSS TORTULA INERMIS

Author
item STARK, LLOYD - UNIV OF NEVADA-LAS VEGAS
item Oliver, Melvin
item MISHLER, BRENT - UNIV OF CALIFORNIA-BERKEL
item MCLETCHIE, D. NICHOLAS - UNIV OF KENTUCKY

Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2006
Publication Date: 11/10/2006
Citation: Stark, L.R., Oliver, M.J., Mishler, B.D., Mcletchie, D. 2006. Generational differences in response to desiccation stress in the desert moss Tortula inermis. Annals Of Botany. 99(1):53-60.

Interpretive Summary: The ability of plant cells to survive water loss is a critical factor in drought tolerance. As part of our ongoing studies on the cellular basis for drought tolerance we are utilizing model plants that can survive the total loss of water from their cells; desiccation tolerant or “resurrection” plants. One of the models we are looking at are the desert mosses of the group Tortula. These are simple plants that allow us to look directly at the effect of the environment on individual plant cells. In this study we are looking at the fundamental differences in desiccation tolerance between the simple leaf cells and those of the more complex reproductive structures. It appears that these plant sacrifices its capability to reproduce in times when water is at a premium by producing structures that are less tolerant to water loss. These effects are important and need to be accounted for when designing strategies to improve drought tolerance in the much more complex plants we use as crops.

Technical Abstract: Actively growing postembryonic sporophytes of desert mosses are restricted to the cooler, wetter months. However, most desert mosses have perennial gametophytes. We hypothesized that these life history patterns are due in part to a reduced desiccation tolerance for sporophytes relative to gametophytes. Gametophytes with attached postembryonic sporophytes of Tortula inermis (early seta elongation phenophase) were exposed to two levels of desiccation stress: one rapid-dry (RD) cycle and two RD cycles, then moistened and allowed to recover, resume development, and/or regenerate for 35 days in a growth chamber. Gametophytes tolerated the desiccation treatments well, with 93% survival through regenerated shoot buds and/or protonemata. At the high stress treatment, a significantly higher frequency of burned leaves and browned shoots occurred. Sporophytes were far more sensitive to desiccation stress, with only 23% surviving after the low desiccation stress treatment, and 3% surviving after the high desiccation stress treatment. While the timing of protonemal production and sporophytic phenophases was relatively unaffected by desiccation stress, shoots exposed to one RD cycle produced shoots more rapidly than shoots exposed to two RD cycles. We conclude that sporophytes of Tortula inermis are more sensitive to rapid drying than are maternal gametophytes, and that sporophyte abortion in response to desiccation results from either reduced desiccation tolerance of sporophytes relative to gametophytes, or from a termination of the sporophyte on the part of the gametophyte in response to stress.