Gravitropic moss cells default to spiral growth on the clinostat and in microgravity during spaceflight

Abstract

In addition to shoots and roots, the gravity (g)-vector orients the growth of specialized cells such as the apical cell of dark-grown moss protonemata. Each apical cell of the moss Ceratodon purpureus senses the g-vector and adjusts polar growth accordingly producing entire cultures of upright protonemata (negative gravitropism). The effect of withdrawing a constant gravity stimulus on moss growth was studied on two NASA Space Shuttle (STS) missions as well as during clinostat rotation on earth. Cultures grown in microgravity (spaceflight) on the STS-87 mission exhibited two successive phases of non-random growth and patterning, a radial outgrowth followed by the formation of net clockwise spiral growth. Also, cultures pre-aligned by unilateral light developed clockwise hooks during the subsequent dark period. The second spaceflight experiment flew on STS-107 which disintegrated during its descent on 1 February 2003. However, most of the moss experimental hardware was recovered on the ground, and most cultures, which had been chemically fixed during spaceflight, were retrieved. Almost all intact STS-107 cultures displayed strong spiral growth. Non-random culture growth including clockwise spiral growth was also observed after clinostat rotation. Together these data demonstrate the existence of default non-random growth patterns that develop at a population level in microgravity, a response that must normally be overridden and masked by a constant g-vector on earth.

An Endogenous Growth Pattern of Roots Is Revealed in Seedlings Grown in Microgravity

“…Previous investigators had shown that protonemata of the moss Ceratodon purpureus exhibited nonrandom spiral growth in microgravity, which is similar to our observation that an endogenous response is masked by gravity (Kern et al, 2005). In a different spaceflight experiment, these workers also noted that amyloplasts were grouped into subapical clusters in the moss protonemata in the flight samples as another nonrandom growth response (Kern et al, 2001).…”

“…The BRIC payload in a similar configuration with the PDFUs had flown on missions STS-87 in NovemberDecember 1997 and STS-107 in JanuaryFebruary 2003 (Kern et al, 2005). Although Discovery was docked to the International Space Station during the STS-131 mission, the BRIC-16 experiment was performed in the middeck area of the space shuttle.…”

“…The BRIC payload (Figs. 1 and 2) in a similar configuration had been used on missions STS-87 and STS-107 Kern et al, 2005). However, in these experiments, light was provided from a red LED, and cultures of the moss Ceratodon purpureus were grown in the BRIC spaceflight hardware .…”

Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications

“…Although bryophytes were included in a proposal of a programme for biological terraforming of Mars [25], the astrobiological potential of bryophytes is still poorly explored [26].…”

A Celebration of Fred David Sack

“…Amazingly after the loss of this spacecraft, the fixed moss samples from Fred's experiment were recovered on the ground. Fred went on to publish a paper (Kern et al, 2005) that demonstrated the existence of default nonrandom growth patterns that developed in microgravity and suggested that this response was overridden and masked by a constant g-vector on Earth.…”