The study of plant responses to touch, particularly the responses of leaves, stems, and roots, has a long history. By contrast, fl oral responses are relatively unexplored. Stigma closure is common in the Bignoniaceae, but the factors infl uencing it are not well understood. We investigated factors infl uencing stigma closure and reopening and its effects on pollen receipt in seven Oroxylum indicum trees near Hat Yai, Thailand. The effects of pressure, conspecifi c and heterospecifi c pollen, and pollen load (the amount of pollen deposited) on stigma behavior were examined in 270 fl owers (of the total 430 fl owers evaluated in the entire study). Pressure alone resulted in faster closure than did conspecifi c pollination and faster reopening than did heterospecifi c pollination. Stigmas never reopened after conspecifi c pollination. Pollen load had no effect on stigma behavior. Stigmas discriminated between conspecifi c and foreign pollen; they reopened only after pollination with the latter. A manipulative experiment revealed that stigma closure did not affect the number of conspecifi c pollen grains received. We also counted pollen tubes in styles that were either hand-supplemented with outcross conspecifi c pollen or open-pollinated. Pollen tube numbers were highest after light pollination (~900 grains), indicating that interference among pollen grains may occur after pollination with very heavy loads ( > 6000 grains). Possible fi tness consequences of these responses are discussed.

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Paphiopedilum niveum (Rchb.f.) Stein, an endangered species, has been listed in CITES Appendix I and its germplasm conservation is required. To improve the regeneration of cryopreserved somatic embryos (SEs), adding 0.1 mM ascorbic acid (AsA) at a critical step during cryopreservation was investigated. The reactive oxygen species (ROS) and malondialdehyde (MDA) contents were also assessed during five steps (preconditioning, 1 st preculture, 2 nd preculture, osmoprotection, and dehydration) of a developed V cryo-plate technique as described briefly. Two-month-old SEs were preconditioned on modified Vacin and Went medium (MVW) containing 0.1 M sucrose for seven days. These SEs were precultured on MVW containing 0.2 M sucrose for one day (1 st preculture) before being transferred to the same medium with 0.6 M sucrose for one day (2 nd preculture). Precultured SEs were embedded on a cryo-plate, incubated in loading solution (LS) with 1.2 M sucrose for 30 min at 25°C and dehydrated with plant vitrification solution 2 (PVS2) for 60 min at 25°C. It was found that applying AsA on day 7 after culture (before the 1 st preculture) could reduce total ROS and MDA levels, leading to a high regeneration percentage (39%) of cryopreserved P. niveum SEs.

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