BackgroundFrequently, in dioecious plants, female plants allocate more resources to reproduction than male plants. Therefore it is expected that asymmetrical allocation to reproduction may lead to a reproduction-growth tradeoff, whereby female plants grow less than male plants, but invest more in defenses and thus experience lower herbivory than male plants.Methodology/Principal FindingsWe tested these expectations by comparing resource allocation to reproduction, growth and defense and its consequences on herbivory in three sympatric dioecious Chamaedorea palms (C. alternans, C. pinnatifrons and C. ernesti-augusti) using a pair-wise design (replicated male/female neighboring plants) in a Mexican tropical rain forest. Our findings support the predictions. Biomass allocation to reproduction in C. pinnatifrons was 3-times higher in female than male plants, consistent with what is known in C. alternans and C. ernesti-augusti. Growth (height and leaf production rate and biomass production) was higher in male plants of all three species. Female plants of the three species had traits that suggest greater investment in defense, as they had 4–16% tougher leaves, and 8–18% higher total phenolic compounds concentration. Accordingly, female plants sustained 53–78% lower standing herbivory and 49–87% lower herbivory rates than male plants.Conclusions/SignificanceOur results suggests that resource allocation to reproduction in the studied palms is more costly to female plants and this leads to predictable intersexual differences in growth, defense and herbivory. We conclude that resource allocation to reproduction in plants can have important consequences that influence their interaction with herbivores. Since herbivory is recognized as an important selective force in plants, these results are of significance to our understanding of plant defense evolution.

Chenopodium L. is a relatively under-studied genus that includes the cultivated seed crop quinoa (C. quinoa Willd.). Quinoa is an allotetraploid (2n = 4x = 36, AABB genomes) that is cultivated by subsistence farmers and commercial growers in the Andean regions of South America. Approximately 60% of a quinoa seed is starch, a glucose polymer that is an important carbohydrate energy source in the human diet. Seed starch is normally composed of amylose and amylopectin in a 1:3 ratio. The accumulation of the amylose fraction of starch is controlled by a single dominant gene in quinoa, GBSSI. We report the sequencing and characterization of the GBSSI gene in 18 accessions of Chenopodium, including Andean quinoa and the related Mesoamerican chenopod domesticate, C. berlandieri subsp. nuttalliae Saff. Two distinct homeologs (GBSSIa and GBSSIb) were identified in the tetraploid accessions, and 19 different alleles were identified, including three null mutants-one in an accession of quinoa and two in a waxy landrace of C. berlandieri subsp. nuttalliae. Expression analysis of the null mutants revealed that GBSSIa and GBSSIb were both strongly expressed late in seed development.GBSSI sequences were used to analyze the phylogenetic relationships between quinoa and other members of the Chenopodium genus. This study and the discovery of Chenopodium GBSSI null-mutants will assist in the development of new Chenopodium crops with novel starches.

This study is a cytogenetic characterization by karyotyping and a determination of the DNA content by flow cytometry of wild populations of Agave cupreata from the Guerrero State, Mexico. Three of the studied populations were diploids (2n = 2x =60) and one population had tetraploid (2n = 4x = 120), pentaploid (2n = 5x = 150) and hexaploid (2n = 6x = 180) plants. Diploid populations had three different structural cytotypes. One population showed polyploid cytotypes. A. cupreata showed a bimodal karyotype of 10 large + 50 small chromosomes in diploids; 20 large + 100 small chromosomes in tetraploids and 25 large + 125 small chromosomes in pentaploids. In diploids, they had secondary constriction in one pair of the large chromosomes and, in the fourth or fifth large homologous chromosome groups, in polyploid plants. The arm ratio, the proportion of different types of large and small chromosomes, the mean of genome length and the asymmetry index of karyotypes clearly varied among diploid and polyploid cytotypes. The pattern of variation among Agave cupreata populations is probably due to rearrangements in the large and small chromosomes of the complement. The diploid populations displayed a 0.63% variation in 2C DNA content. The mean 2C DNA content was 7.88 pg; 1Cx value = 3.94 pg in diploids of Agave cupreata. Tetraploids had 2C = 16.54 pg DNA, i.e. approximately four times the 1Cx value; 2C DNA amounts of pentaploid and hexaploid were equal to 20.42 and 23.92 pg DNA, respectively. These values are also multiples of 1Cx value, indicating a relationship between the ploidy level and the 2C DNA content. The results shown are basic and useful information to develop biotechnology and breeding approaches for Agave cupreata.