Growth of C3 and C4 Perennial Grasses under Reduced Irradiance

Abstract

Several studies have compared C3 and C4 species for response to water and temperature regimes. Little comparative information exists, however, on growth responses of C3 and C4 species to irradiance regime. The objective of this study was to determine adaptive responses of C3 and C4 grasses to irradiance regime. Three C3 and two C4 perennial forage grasses were field—established near Ames, IA, and grown under 37, 70, and 100% of full sunlight by use of polypropylene shade cloths. Morphology and growth measurements were conducted three times at ⊄21‐d intervals each year for 2 yr. Net leaf CO2 exchange rate (CER) was measured for one C3, and one C4 grass. Specific leaf weight increased and leaf‐area ratio decreased with increasing irradiance similarly in all five species. Responses of herbage yield, shoot dry weight, and crop growth rate to irradiance were two to three times greater for C4 grasses than for C3 grasses. Responses of CER to irradiance were greater for the C4 grass than for the C3 grass. Morphological adaptive responses were similar for C3 and C4 grasses, but responses closely related to photosynthesis (e.g., CER, growth rate, and herbage yield) were affected more in C4 than in C3 species.

Tree canopy effect on grass and grass/legume mixtures in eastern Nebraska

“…An inverse polynomial model was analyzed and found to fit the data well. The rapidly increasing BB yield at higher LT agrees with the findings of Kephart et al (1992) and Lin et al (1999), although they reported points of inflection at lower light levels than what we found. The relationship described in Fig.…”

“…1). The increasing SB yields with increased light levels were in accordance with other studies that reported linear increases of cool-season grasses as light levels increased (Kephart et al 1992;Lin et al 1999). June yields of BFT in the SB/BFT plots were correlated to LAI measurements taken on 4 June 2001 (Table 4, Eq.…”

“…A silvopasture system provides an overall greater economic return for the landowner per hectare than either timber or cattle alone (Pearson and Whitaker 1974;Clason 1995;Gold et al 2000). In the United States, the majority of research with silvopasture systems has been conducted in the southeast and northwest, and has focused on forage and/or animal performance under various canopy covers of different conifer tree species or the forage response to different light levels, whether imposed by shade cloth or tree canopy (Pearson and Whitaker 1974;Garrett and Kurtz 1983;Lewis et al 1985;Kephart et al 1992;Kephart and Buxton 1993).…”

“…Cool-season plants generally respond to shade by investing a greater proportion of synthetic capacity into increasing overall leaf chlorophyll content (Boardman 1977), whereas warm-season plants respond by increasing specific leaf area (Murchie and Horton 1997). Even with greater specific leaf area, shaded leaves of C 4 plants intercept less light than full sunlight leaves and net photosynthesis declines because of low irradiance (Kephart et al 1992). …”

Comportamento produtivo e características nutricionais do capim-braquiária cultivado em consórcio com milho

“…Norton et al (1991) afirmaram que a diferença entre a digestibilidade in vitro da MS de forrageiras que cresceram em plena insolação ou com restrição à luminosidade foi pequena e sem significância estatística. Kephart et al (1992) e Kephart & Buxton (1993) relataram aumentos de 5% na digestibilidade da MS em decorrência desse efeito. Samarakoon et al (1990b) não encontraram efeito significativo do sombreamento sobre a digestibilidade in vivo e in vitro da MS. No entanto, segundo Masuda (1977), citado por Lin et al (2001), a digestibilidade da MS de gramíneas e leguminosas diminui com a redução da intensidade luminosa.…”