The Physiological Mechanism Of The Style Curvature In Alpinia (Zingiberaceae)

The style curvature of Alpinia is a peculiar floral organ movement during flowering. Each species of Alpinia have two morphs whose directions of style curvature are opposite at the same floral development stage. The styles of each morph have two processes of curvature which the directions are absolutely opposite.Only the style tip (about 25% of total style) had the ability of curvature. We found that the style structures were similar for two morphs although they curved toward opposite directions. The diameter of curvature tissue was bigger than that of non-curvature part (diameter of curvature part of anaflexistylous morph is 0.83±0.08 mm, non-curvature part is 0.54±0.05 mm; for cataflexistylous morph are 0.85±0.07 mm, 0.58±0.06 mm respectively). There was no difference in anatomic structure of style between two morphs—in curvature part , the adaxial side have two vascular bundles, and more layers of cell, but the abaxial side just has one bundle, however, in non-curvature part, the difference was very small in cell layer between adaxial side and absxial side. The anatomic structure was different between curvature part and non-curvature part. The cells in abaxial side of curvature part were narrow and long, and the cell walls of them were thick. The adaxial side of the curvature part, besides owning the cells like that of abaxial side, had cells with irregular shape, bigger diameter and thin cell wall. But the adaxial side and abaxial side of non-curvature part were similar; all cells in them are narrow and long.In all the stimuli that may affect the style curvature, touch, gravity, pollination and the pollen sac dehiscence didn't work, but temperature and light can affect curvature. Low temperature can cause the curvature slower, but the style curvature was not thermonasty which is defined that the movement of plant organ in response to a"change"in temperature. The styles could curve under"constant"temperature, even if the low temperature. Effect of light on style curvature was very complex. For cataflexistylous morph, the first curve could complete whether in dark or light. Before the second curvature, the magnitude of curvature in light was larger than that in dark if the styles were sampled before dawn; if the styles sampled after lit several hours, the magnitude of curvature was equal in dark and light. For anaflexistylous morph, the first curvature can be skipped in darkness, but if put in light, styles curved upward directly, loosing the first process of downward curvature. Before the second curvature, the styles didn't begin to curve in dark if sampled before dawn. If styles were sampled after illuminated several hours, the degree they curved in dark was similar to that always in light. These results indicated that the style curvature of Alpinia was nastic movement, because they just curved upward or downward relative to the position of anther. The curvature of cataflexistylous morph was not induced by external stimuli, and it was controlled by endogenous rhythm. The curvature of cataflexistylous morph could happen at constant environment, but can be reset by light and temperature, and may have temperature compensation, so this process may be controlled by biological clock. The stimuli that led to the curvatures of anaflexistylous morph were different: the first curvature was controlled by biological clock, like the cataflexitylous morph; the second curvature was controlled by light.The asymmetrical distribution of IAA was the basis for differential growth of the plant organ movements. We found that NPA and TIBA, two inhibitors of IAA transport can affect style curvature. NPA treatment before every curvature made the anaflexitylous curve more bending. Before the first curvature, NPA treatment made the cataflexistylous curve upward firstly, but it no longer curved downward. Before the second curvature, NPA and TIBA treatment almost inhibited the downward curvature if sampled before dawn. If sampled about 10:30 am, the style curved more bending than that sampled before dawn. All the results indicated that auxin and auxin polar transport play great role in style curvature. Since the auxin transport worked in style curvature, the asymmetrical distribution of IAA might appear between adaxial and abaxial side, but this study could not be detected by immunoenzymatic technique, the possible reason is the difference of IAA gradient between the two sides was very weak. Calcium distribution changed during the style curvature of Alpinia. Before flowering, the first curvature to the second curvature, the concentration of loosing bound calcium in apoplast increased firstly, and then decreased. Between adaxial and abaxial cell walls, the calcium distribution was symmetrical unlike that in roots or shoots that was oriented horizontally. The inhibition of calcium on cell wall loosing between adaxial and abaxial sides was not different. The changes of loosing bound calcium concentration in cell wall maybe induced the free calcium ion in cell.