GROWTH AND BIOMASS PARTITIONING OF MAIZE DURING VEGETATIVE GROWTH IN RESPONSE TO STRIGA HERMONTHICA INFECTION AND NITROGEN SUPPLY

Abstract

The effect of the root hemiparasitic angiosperm Striga hermonthica on the gowth, photosynthesis and partitioning of biomass in maize was studied in glasshouse experiments in two seasons. In both seasons, nitrogen was applied to the plants at rates equivalent to 20, 60 and 120 kg ha 71 . There was no signi®cant Striga6nitrogen interaction on the responses measured. Averaged across all nitrogen treatments, maize plants infected with S. hermonthica had smaller leaf areas and accumulated less biomass, than did uninfected plants. The leaf area of infected and uninfected plants increased asymptotically from emergence to the ®nal harvest (about the 18-leaf stage) at which time the leaf area of infected plants was 63% that of uninfected plants. The rates of photosynthesis of the youngest, fully expanded leaves of infected plants, averaged across N treatments, were signi®cantly lower than for uninfected plants. However, stomatal conductance and the sub-stomatal CO 2 concentration were unaffected by Striga infection. Although infection with Striga signi®cantly reduced shoot biomass (dry weight at ®nal harvest was 37% that of uninfected plants in 1995 and 63% in 1996), there were no signi®cant effects of Striga infection on root biomass so that the infected plants partitioned a signi®cantly greater proportion of their total biomass to roots compared with the uninfected plants. The allometric coef®cients, though, were similar for both infected and uninfected plants. Averaged across infected and uninfected plants, application of nitrogen increased total leaf area per plant and root and shoot biomass but did not change the proportion of total biomass partitioned to roots. These results did not show a major effect of nitrogen on the relative growth response of maize to infection with Striga.introdution Striga hermonthica (Scrophulariaceae) is a root hemi-parasite of Poaceae in the semiarid tropics and an important weed of maize, sorghum, millet and rice crops. Symptoms of Striga infestation include reduced vigour, stunted growth, wilting and chlorosis, with yield losses of between 30±50% or total crop failure under varying

Effects of weed control through cowpea intercropping on mayze morphology and yield

“…This is corroborated by the observations of Begna et al (2001). Decreased maize stem diameter due to the presence of weeds has also been reported (Souza, 1994) as well as reduced maize leaf area (Aflakpui et al, 2002).…”

Growth and yield of corn grain and green ear in competition with weeds

“…Effect of treatments on mean plant leaf area was similar to leaf width results (Table 2), that is, there was an effect of the age x weed control interaction. Corn leaf area reductions (Aflakpui et al, 2002) caused by Striga hermonthica, a parasite species on corn, were also observed by other authors. Different authors (Ford & Pleasant, 1994) also verified a reduction in the number of corn leaves caused by weeds.…”

“…This means that corn yield losses due to competition with weeds for incident PFD cannot be explained by reduced photosynthesis rates in lower leaves shaded by weeds. Such loss is more likely explained by a reduction in leaf area, as observed in this research (Table 2) as well as in other studies (Aflakpui et al, 2002). It has been verified (Tollenaar et al, 1997) that high competition by weeds reduced LAI in corn at the blooming stage by 15%.…”

Effects of weed "Reestablishment" after hoeing on corn yields

“…In fact, some authors (Aflakpui et al, 2002) observed leaf area reductions due to competition with weeds.…”