Early detection of neighbour plants by phytochrome perception of spectral changes in reflected sunlight

Abstract

We have tested the hypothesis that a plant may detect the ptesence of a neighbour, befote being shaded by it, thtough the petception of the spectt-al composition of reflected sunlight. Within seedlitig canopies the red : far-red t-atio (R : FR) of the light received by a sensor with a geotnett-y appt-oxitnating that of a stetn was significantly teduced by selective reflection. This effect was observed befote any reduction in the atnount of photosytithetic light energy received by an individual seedling could be detected. Stnall gt-een fences of grass, east-west orientated, alteted the specttal distribution of the light on the north (sunlit) side of thetn. Fully illuminated seedlings of Sinapis alba giown on the north side of these gt-een fences produced longer internodes and had a lower leaf: stetn dry weight ratio than those grown in ftont of fences of bleached grasses. A sitnilar tedistribution of gtowth was elicited in seedlings of Chettopodinm album. Datura ferox and S. alba growing iti full sunlight by exposing plants to additional small quantities of fat-red reliected by seleetive tnirtot-s. These t-esults suggest that the change in the R: FR ratio serves as an early warning signal of oncotning cotnpetition.

Growth and crown architecture of two aspen genotypes exposed to interacting ozone and carbon dioxide

“…Responses to neighbours via structural crown interaction may be crucial for species composition within communities (Küppers & Lange, 1987;Tremmel & Bazzaz, 1995;Umeki, 1997;Suzuki, 2002). Plants detect neighbours by changes in light quality, and they may alter crown architecture before light availability becomes reduced (Ballaré et al, 1988(Ballaré et al, , 1987. Yokozama et al (1996) pointed out that the difference in crown shapes of conifers (conic) and angiosperm broadleaved trees (spheroidal) may ensure the coexistence of both tree types in boreal and sub-boreal zones.…”

Foraging for light: photosensory ecology and agricultural implications

“…About a decade ago, two studies of the dynamics of plant morphogenesis in seedling stands demonstrated that plants begin responding to the proximity of other plants well before they are shaded by their neighbours (Casal, Sanchez & Deregibus 1986;Ballare et al 1987). Ballare et al (1987Ballare et al ( , 1990 proposed that FR radiation reflected by neighbouring plants played an important role as an early warning signal of competition in growing canopies.…”

“…Ballare et al (1987Ballare et al ( , 1990 proposed that FR radiation reflected by neighbouring plants played an important role as an early warning signal of competition in growing canopies. This hypothesis was soon supported by a number of studies that demonstrated the following: (I) plants grown under full sunlight in the field respond to augmented FR radiation with increased elongation and apical dominance (Ballare et al 1987); (2) FR provides a reliable signal of the presence of neighbours well before plants experience a reduction in light availability (e.g.…”

The function of phytochrome A

“…Seedlings of various species are able to respond to early warning signals of neighbouring plants provided by FR reflected in green tissues (Ballare et al 1987). These R/FR signals anticipate mutual plant shading in growing canopies, i.e.…”