Photomodulation of axis extension in sparse canopies. role of the stem in the perception of light-quality signals of stand density

• Published in: Plant physiology (Bethesda) Vol. 89; no. 4; pp. 1324 - 1330
• Main Authors: Ballaré, Carlos L., Scopel, Ana L., Sánchez, Rodolfo A.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.04.1989
• Subjects: Biological and medical sciences; brassica alba; canopy; couvert; crassulaceae; cubierta de copas; datura; feuille; Fundamental and applied biological sciences. Psychology; growth rate; hojas; indice de crecimiento; instrument; instrumentos; instruments; Internodes; Leaves; light; lumiere; luz; Mirrors; Photons; Physical agents; Plant physiology and development; Plants; plantulas; plantule; Seedlings; Spectral energy distribution; stems; Sunlight; tallo; taux de croissance; tige; Vegetation canopies; Vegetative apparatus, growth and morphogenesis. Senescence; Visible spectrum; Crassulaceae; Environmental factor; Plant leaf; Stem; Cruciferae; Brassica alba; Dicotyledones; Light; Angiospermae; Phytochrome; Development; Spermatophyta; Solanaceae; Population density; Elongation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.89.4.1324

A fiber optic probe inserted into plant tissues was used to investigate the effects of canopy density on the light environment in different organs. The red:far-red ratio inside the stem of Datura ferox L. seedlings and the estimated phytochrome photoequilibrium were strongly reduced by the presence of neighbors forming canopies too sparse to cause any mutual shading at the level of the leaves. In such canopies, change in plant density had little effects on the light regime inside the leaves of the succulent Aeonium haworthii (S.D.) Webb et Berth., particularly when the lamina was kept nearly normal to the direct rays of the sun. In field experiments using D. ferox and Sinapis alba L. seedlings, the elongation of the internodes responded to various types of localized light-quality treatments that simulated different plant densities in sparse canopies . The responses were quantitatively similar to those elicited by changes in plant density. The evidence supports the hypothesis that, in stands formed by plants of similar size, the red:far-red ratio of the light that impinges laterally on the stems is among the earliest environmental cues that allow plants to detect local canopy density and adjust axis extension accordingly.