Summary
We studied the effects of density on the dynamics of seedling growth and canopy microclimate within experimental stands composed of Datura ferox L. seedlings grown in individual pots. Interception of photosynthetically active radiation (PAR) by seedlings was evaluated either indirectly, by measuring leaf area, proportion of leaf area shaded by neighbouring individuals and laminar orientation with respect to sunlight, or directly, by measuring PAR at individual leaves at their natural angle of display. An integrating cylinder, with a geometry approximating that of a stem, was used within the canopies to measure the red:far-red (R:FR) ratio of the light flux from all compass points parallel to the soil surface. Seedlings responded rapidly (i.e. 1–2 weeks) to increased density by producing longer internodes and partitioning more dry matter to stems relative to leaves. These responses were observed before either PAR interception of growth rate were reduced by the presence of neighbours. Conversely, morphogenetic adjustment was preceded by a consistent effect of plant density on the R:FR ratio of the light received by the integrating cylinder. Air and soil temperature were not affected by density in these experiments. Differences in wind velocity within the canopy associated with plant density were avoided by the experimental procedure. The results support the idea that the drop in R:FR ratio of the light flux parallel to the ground — e.g. reflected sunlight — is an early signal that allows rapid adjustment of plant form to changes in canopy structure.
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References
Ballaré CL, Sánchez RA, Scopel AL, Casal JJ, Ghersa CM (1987) Early detection of neighbour plants by phytochrome perception of spectral changes in reflected sunlight. Plant Cell Environ 10:551–557
Casal JJ, Sánchez RA, Deregibus VA (1986) The effect of plant density on tillering: the involvement of R/FR ratio and the proportion of radiation intercepted per plant. Exp Environ Bot 26:365–371
Casal JJ, Sánchez RA, Deregibus VA (1987) The effect of light quality on shoot extension growth in three species of grasses. Ann Bot 59:1–7
Constable GA (1986) Growth and light receipt by main stem cotton leaves in relation to plant density in the field. Agric For Meteorol 37:279–292
Deregibus VA, Sánchez RA, Casal JJ, Trlica MJ (1985) Tillering responses to enrichment of red light beneath the canopy in a humid natural grassland. J Appl Ecol 22:199–206
Grime JP (1979) Plant strategies and vegetation processes. John Wiley & Sons, Chichester
Harper JL (1977) Population biology of plants. Academic Press, London
Holmes MG, Smith H (1977a) The function of phytochrome in the natural environment. II. The influence of vegetation canopies on the spectral energy distribution of natural daylight. Photochem Photobiol 25:539–545
Holmes MG, Smith H (1977b) The function of phytochrome in the natural environment. IV. Light quality and plant development. Photochem Photobiol 25:551–557
Hunt R (1982) Plant growth curves. University Park Press, Baltimore
Hurlbert SH (1984) Pseudoreplication and the design of ecological field experiments. Ecol Monogr 54:187–211
Kasperbauer MJ (1971) Spectral distribution of light in a tobacco canopy and effects of end-of-day light quality on growth and development. Plant Physiol 47:775–778
Lecharny A (1979) Phytochrome and internode elongation in Chenopodium polyspermum L. Sites of photoreception. Planta 145:405–409
Marzoca A (1979) Manual de Malezas. Hemisferio Sur, Buenos Aires
Mc Intyre GI, Boyer JS (1984) The effect of humidity, root excision, and potassium supply on hypocotyl elongation in dark grown seedlings of Helianthus annus. Can J Bot 62:420–428
De Miguel LC, Soriano A (1974) The breakage of dormancy in Datura ferox seeds as an effect of water absorption. Weed Res 14:265–270
Mohr H (1972) Lectures on photomorphogenesis. Springer-Verlag, Berlin Heidelberg
Morgan DC, Smith H (1978) The relationship between phytochrome photoequilibrium and development in light grown Chenopodium album L. Planta 142:187–193
Morgan DC, Smith H (1979) A systematic relationship between phytochrome-controlled development and species habitat, for plants grown in simulated natural radiation. Planta 145:253–258
Morgan DC, Smith H (1981) Control of development in Chenopodium album L. by shadelight: The effect of light quantity (total fluence rate) and light quality (red:far red ratio). New Phytol 88:239–248
Morgan DC, Child R, Smith H (1981) Absence of fluence rate dependency of phytochrome modulation of stem extension in light-grown Sinapis alba L. Planta 151:497–498
Morgan DC, O'Brien T, Smith H (1980) Rapid photomodulation of stem extension in light-grown Sinapis alba L. Studies on kinetics, site of perception and photoreceptor. Planta 150:95–101
Neel PL, Harris PW (1971) Motion-induced inhibition of elongation and induction of dormancy in Liquidambar. Science 173:58–59
Smith H (1982) Light quality, photoperception and plant strategy. Annu Rev Plant Physiol 33:481–518
Travis RL, Reed R (1983) The solar tracking pattern in a closed alfalfa canopy. Crop Sci 23:664–668
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Ballaré, C.L., Sánchez, R.A., Scopel, A.L. et al. Morphological responses of Datura ferox L. seedlings to the presence of neighbours. Oecologia 76, 288–293 (1988). https://doi.org/10.1007/BF00379965
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DOI: https://doi.org/10.1007/BF00379965