Size-dependent reproductive effort in Amaranthus retroflexus: the influence of planting density and sowing date

Abstract

Size-dependent reproductive effort is an important component of plant fitness. The responses of reproductive effort to environmental factors in Amaranthus retroflexus L. were measured in two experiments. A wide range of selection pressures were generated by manipulating the sowing date (29 April, 23 May, 18 June, and 14 July) and planting density (13.4, 36, 121, and 441 plants·m–2). Allometric analysis between reproductive biomass and vegetative biomass across treatments showed that reproductive effort increased with size in response to different planting densities but decreased with size in sowing dates experiment. The allometric exponent between treatments was not influenced by planting densities but had significant variation with sowing date. Total branch length could explain most of the variation of reproductive accumulation and allocation in planting density experiments. For the plants with different sowing dates, total branch length was the main determinant of reproductive biomass, while reproductive effort mainly depended on the number of primary branches per unit stem mass. Architectural constraints with size result in size-dependent reproduction. Size-dependent reproduction in A. retroflexus was influenced by available resources and environmental conditions through the mechanisms of self-regulation of architectural traits.

Biomass allocation to vegetative and reproductive organs of Chenopodium acuminatum Willd. under soil nutrient and water stress

“…When the relationships between different organs do not shift or only shift along the common slope, the plasticity is "apparent", which means that the biomass allocation holds the consistent patterns in different environments (Wang et al 2006, Weiner 2004). These results indicated that root : shoot ratio did not have plasticity in response to soil nutrient.…”

“…This ability is called plasticity. Many researchers showed that allometric relationships are affected by environment (Allen et al 2008, Bernacchi et al 2007, Shipley and Meziane 2002, Wang et al 2006. The environment may only affect the plant size, but does not change the allometric relationships between different biomass.…”

“…However, the growth ratio of plant may vary with the plant size and plant may change the pattern of biomass allocation themselves in response to variable environments (Geng et al 2007, McConnaughay and Coleman 1999, Weiner 2004) which is so-called ''true'' plasticity. The "apparent" plasticity exists in many plants (Geng et al 2007, Wang et al 2006. It is difficult to distinguish between "apparent" and "true" plasticity without a careful study of allometry Coleman 1999, Wang et al 2006).…”

Allometric Effects of Agriophyllum squarrosum in Response to Soil Nutrients, Water, and Population Density in the Horqin Sandy Land of China

“…Allometric analysis can incorporate plant size into computations of plant biomass to help minimize bias when comparing allocation patterns (Wang et al 2006;Allen et al 2008). Many species show allometric relationships among the biomasses of different organs (Naumburg et al 2001;Bernacchi et al 2007).…”

Costs of reproduction in life history of a perennial plant Carex secalina

“…Thus, the relative reproductive investment reaches its maximum in the second year of the plant's reproduction. In some studies, reproductive effort increased as plants grew [28,29], but more often it was found that reproductive effort was size-related [30][31][32][33].…”