Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook.f. & Thomson (Polygonaceae)

The Bracts of Saussurea velutina (Asteraceae) Protect Inflorescences from Fluctuating Weather at High Elevations of the Hengduan Mountains, Southwestern China

“…Due to the thinner bracts and lack of chloroplast differentiation, bracts in S. velutina may scatter and absorb less radiation than green leaves. In addition, bracts in S. velutina showed a lower reflectance in the IR range than rosette leaves, a result almost identical to the reflectance in bracts and rosette leaves reported for R. nobile (Omori et al, 2000). Based on the similarities between the anatomy and reflective spectra of S. velutina, R. nobile, and R. alexandrae, it is likely that the bracts of S. velutina facilitate the transmission of IR radiation which is absorbed efficiently by the inflorescence and results in an elevated temperature within the inflorescence, similar to what Omori et al (2000) and Tsukaya (2002) reported for the bracts of R. nobile and R. alexandrae.…”

“…Bracts in S. velutina have only one layer of mesophyll with neither palisade nor spongy form, and therefore are different from rosette leaves both in structure and function. Similar anatomical characters have been described for bracts in R. nobile and R. alexandrae (Omori et al, 2000;Tsukaya, 2002). Due to the thinner bracts and lack of chloroplast differentiation, bracts in S. velutina may scatter and absorb less radiation than green leaves.…”

“…Based on measurements on a single inflorescence on R. nobile in Nepal, Omori and Ohba (1999) reported that bracts on the inflorescence elevated the temperature of floral tissues and had insulative effects. In addition, the large bracts of R. nobile and R. alexandrae have positive effects on the control of sunlight penetration and protect the inflorescence from ultraviolet radiation (Terashima et al, 1993;Omori and Ohba, 1996;Omori et al, 2000;Tsukaya, 2002;Iwashina et al, 2004).…”

Partly transparent young legume pods: Do they mimic caterpillars for defense and simultaneously enable better photosynthesis?

“…A well-known case of translucent leaves in order to improve photosynthesis, to allow warming of the tissues and even to improve reproduction is that of the glasshouse plants of several Rheum species of the Himalayas. [19][20][21][22] While improving their survival and sexual reproduction by being translucent, these glasshouse plants decrease the danger of UV-B radiation damage by expressing high levels of flavonoids that absorb it. 21,22 Improving photosynthesis also seems to operate when the fast-growing young and partly transparent pods discussed here can perform photosynthesis in both external and internal layers.…”

Leaf and floral heating in cold climates: do sub-Antarctic megaherbs resemble tropical alpine giants?

“…Sub-Antarctic megaherbs possess similar leaf and growth form traits that have been identified by Reich et al (1999) in other giant herbaceous species across six biomes. These include giant Lobelia species, Senecio species and Rheum nobile; all exhibit giant growth forms with accompanying traits such as hairs which are shown to provide mini-''glasshouse'' effects Omori et al 2000;Antonelli 2009). …”