The influence of photoperiod on the dry matter production of grasses and cereals

摘要: summary Photoperiod can affect the growth and development of grasses cereals in three distinct ways: by providing a cue for start reproductive phase, modifying rate once established, causing changes leaf area expansion dry-matter production which are not necessarily related to reproduction. This review, draws heavily on work with from high latitudes Scandinavia, deals mainly this third influence photoperiod, documenting range observed effects plant physiology, drawing results other systems help exploring underlying mechanisms. It is difficult devise experimental treatments differ only daylength but involve realistic daily inputs photosynthetically active radiation (PAR), avoid possible interactions shading responses. In natural environment, photoperiod confounded supply radiant energy, spectral composition solar at beginning end each day varies latitude. It concluded that use daylit phytotron chambers extension low-irradiance incandescent lamps most practical solution complex problem. A survey experiments conducted under irradiances showed exposure plants temperate high-latitude longer days, without increasing PAR, resulted substantial increases (up 200%) production, even greater area. These effects, were common vegetative plants, tended be marked lower temperatures. Growth analysis that, general, enhancement was consequence ratio which, turn, caused specific rather than weight ratio. Higher rates were, therefore, result improved interception although, many experiments, net assimilation lower. Photoperiodic stimulation generally associated an unchanged or increased shoot: root ratio, reduction number tillers per plant, numbers leaves tiller, sheaths blades. Increases blade length, epidermal cell although there also evidence division, tissue succulence. photoperiodic positive feedback system, additional photosynthate first develop long days invested progressively larger leaves. Studies CO2 exchange suggest decreases could explained terms cells amount chlorophyll unit The fact PAR indicates swards, effect will shown spring regular defoliation. Some have full developmental induced equally exogenous application gibberellins. findings consistent gibberellins cellular level (loosening walls, etc.) it too early conclude endogenous play part chain events perception signal leading leaves. The originating maritime environments 52° N northwards suggests response adaptation cool latitude summer. more likely (short-day) depression growth, facilitates cold-hardening these autumn, important. Grasses equipped grow well during growing season latitudes, because they programmed recognize correct subject winterkill.