Differences in the carbon consumption in reproductive structures of a dioecious neotropical palm C. alernans in Los Tuxtlas, Veracruz, Mexico

Background/Question/Methods Dioecious plants are defined as populations of plants with staminate flowers produced on some individuals and pistillate flowers on other individuals. The separation of the reproductive functions has consequences in resource allocation patterns. Commonly, female plants allocate a greater amount of biomass and nutrients to the production of fruits. However, measurements of biomass/nutrients are static and they do not consider the dynamics of carbon loss or gain. Consequently, the cost of the reproduction are underestimated in measurements of biomass. In dioecious plants carbon assimilation by reproductive structures has not been explored. The objective of the present study is to determine the reproductive effort via carbon dynamics of male and female plants during the time of flowering and maturation of fruits. This study was conducted at the Los Tuxtlas field station, in the state of Veracruz, Mexico. We randomly chose 10 male-female pairs of plants of the doiecious palm Chamaedorea alternans in October, 2005. We measured the respiration rates of leaves and reproductive structures during the maturation of flowers and fruits. We measured carbon assimilation with an infrared gas analyzer. We considered reproductive effort according to the biomass of the structures and carbon consumption.

Results/Conclusions The results showed that the net rate of respiration differs depending on the stage of development of the reproductive structures (F = 10.62, P < 0.0001). The female and male structures prior to antesis, as well as the male inflorescences in anthesis, demand a high proportion of carbon for their maturation in contrast to early stages of development of male and female inflorescences. The reproductive effort calculated in percentage terms shows significant differences between categories (F= 4.71, P= 0.0027). Plants with male reproductive structures with advanced degree of development show the greatest reproductive effort in terms of carbon consumption. Nevertheless, female plants maintain carbon consumption for a longer period, since fruit maturation takes nine months (after flowering). In conclusion, the cost of the reproduction, measured in terms of carbon consumption, is greater for female plants. Complementary studies with this system shows that differences in allocation to reproduction, has consequences on plant investment to growth and defense. In female plants greater allocation of resources to reproduction is likely to negatively impact growth because resources that could be used for the production of new leaves, stems and roots are shunted to the production of flowers, fruits and seeds.