Nectar secretion pattern and effects of nectar removal were analyzed in six hummingbird‐pollinated Argentinean Pitcairnioideae: Abromeitiella brevifolia. A. lorentziana, Deuterocohnia longipetala. Dyckia floribunda, D. ragonesei and Puya spathacea. Flower lifetime was determined in each case. Nectar volume, concentration and sugar production were measured from bud opening till fading of flowers at different time intervals according to the species' flower life‐span. Nectar volume varies while nectar concentration and cumulative sugar production increase as a function of flower age in all the studied species. In general, total nectar volume and concentration values can be affected by periodic removal, but total sugar production is unaffected. Only in Puya spathacea did periodic nectar harvesting reduce the total amount of sugar produced.

Mitotic chromosomes of 13 species included in So/anum sect. Lasiocarpa were studied. All species have 2n = 24. The chromosome numbers of S. stagnate, S. felinum, and S. repandum are reported for the first time. Statistical analyses of chromosomes, genome length, and centromere position yielded estimates of karyotype composition and asymmetry. A generalized karyotype of the section shows that most of the chromosomes are metacentric (73%) or submetacentric (25.6%). Two pairs of subtelocentric chromosomes are present only in S. sessi/iflorum. Satellites are quite common, characterizing chromosomes for ten species and are attached to the short arms of either m or sm chromosomes. They could be seen in 10% to 70% of the cells. Only S. pseudo/ufo bears two satellited chromosomes, one of them attached to a long chromosome arm. Although the section is chromosomally quite homogeneous, species can be distinguished by karyotype formula, presence of satellites in a particular chromosome pair, and total chromosome length. There are no indications of major chromosomal rearrangements within the section. Using cytological data exclusively, cluster analysis indicates S. sessi/iflorum is isolated in the section. So/anum candidum and S. vestissimum are somewhat isolated as well and have unique karyological traits. So/anum pectinatum has a peculiar karyotype, but in the phenogram it is not particularly separated. Karyotype features suggest that morphological differentiation was not always followed by chromosomal divergence. The origin ofthe domesticated S. quitoense is no further elucidated by our data.

Some aspects of the reproductive biology of Ligaria cuneifolia have been studied, addressing the following questions: (i) Are there temporal differences in the female and male functions? (ii) How do nectar composition, volume, concentration, and amount of sugar vary throughout the flower lifetime? (iii) How does the plant respond to nectar removal? (iv) What is the breeding system of this species? Flowers last 4 days. There is a predominance of the male function in the first days and of the female function in the last days. Chemical composition of nectar varies throughout the flower lifetime; there is a constant decrease in sucrose along with an increase in glucose. Nectar is secreted during nights, and every secretion period is followed by a cessation interval. After the final cessation, a period of active resorption follows. During the mostly male phase of the flower, nectar has more sucrose than hexose, its secretion is discontinuous, and nectar removal reduces the rate of nectar production. During the mostly female phase, nectar has more hexose than sucrose, its secretion ceases, nectar removal does not affect nectar production, and a resorption period is inferred. Tests for spontaneous autogamy and apomixis were negative. Low fruit set is obtained when autogamous, geitonogamous, and xenogamous hand pollinations are performed on flowers less than 2 days old compared with flowers at least 3 days old (0, 15, and 47% versus 19, 37.5, and 89%, respectively). These results indicate the the reproductive system of L. cuneifolia is primarily xenogamous, but reproductive success is related to flower age. Keywords: Loranthaceae, Ligaria, nectar chemistry, breeding system, flower phenology, reproductive biology.

Nectar secretion pattern and effects of nectar removal were compared in three Argentinean Solanaceae: Nicotiana glauca, which is hummingbird pollinated, and Nicotiana longiflora and Petunia axillaris, which are sphinx moth pollinated. Nectar volume, concentration, and sugar production were measured at different time intervals according to the species' flower life span. Nectar volume and total sugar production increased as a function of flower age in both species of Nicotiana analyzed; however, these parameters were quite stable in P. axillaris. This species produced less nectar and nectar sugar than the other two. When all sets with nectar removal were compared with the controls, significant differences were found in nectar volume and quantity of nectar sugar in N. longiflora, and in sugar concentration in P. axillaris. In the latter, the observed difference did not affect the total amount of sugar secreted. Nicotiana glauca did not show any significant difference in the parameters analyzed. Total nectar production was inhibited by periodic removal in N. longiflora, while in N. glauca and P. axillaris it was unaffected. Key words: nectar secretion pattern, nectar removal, Nicotiana, Petunia, Solanaceae.

GALETTO, L., and BERNARDELLO, L. M. 1992. Extrafloral nectaries that attract ants in Bromeliaceae: structure and nectar composition. Can. J. Bot. 70: 1101 -1106. The occurrence of extrafloral nectaries in some species of Bromeliaceae (subfam. Pitcairnioideae) is reported for the first time in the following plants from central and northern Argentina: Deuterocohnia longipetala, Dyckia ferox, Dyckia j7ori-bunda, Dyckia aff. gilliesii, Dyckia ragonesei, and Dyckia velascana. Ants are attracted to the extrafloral nectar that is secreted in a very high concentration (around 80% weight to total weight) by nonstructural, nonvascularized nectaries located in the outer verticil of tepals. They do not possess a specially differentiated nectariferous tissue and the exudate is probably secreted through paracytic and anomocytic stomata. Sugars and amino acids were detected in the nectar, but alkaloids, reducing acids, proteins, phenols, and lipids were not. Amino acid concentration ranged from 121.3 to 975 pglmL. In all the species there was a high concentration of sucrose (97.2-loo%), whereas glucose and (or) fructose were absent or present in a small amount (0.4-1.5%). GALETTO, L., et BERNARDELLO, L. M. 1992. Extrafloral nectaries that attract ants in Bromeliaceae: structure and nectar composition. Can. J. Bot. 70 : 1101 -1106. Les auteurs rapportent pour la premibre fois l'existence de nectaires extrafloraux chez certaines espbces de Bromeliaceae (sous-fam. Pitcairnioideae) observts sur des plants venant du centre et du nord de 1'Argentine : Deuterocohnia longipetala, Dyckia ferox, Dyckia floribunda, Dyckia aff. gilliesii, Dyckia ragonesei et Dyckia velascana. Les fourmis sont attirtes par le nectare extrafloral secrttt en concentrations trbs Clevtes (environ 80% en poids i poids total) par des nectaires nonstructuraux et sans vascularisation, localists dans le verticille externe des ttpales. On y trouve aucun tissu nectarifbre sptcial et difftrencit, et l'exsudat est probablement secrttt par des stomates paracytiques et anomocytiques. On trouve des sucres et des acides amints dans le nectare mais les alcaloides, les sucres rtducteurs, les prottines, les phtnols et les lipides sont absents. Les concentrations en acides amints vont de 121,3 i 975 pglmL. Chez toutes les espbces, le sucrose est present en fortes concentrations (97,2-100%) alors que le glucose et (ou) le fructose sont absents ou presents en faibles quantitts (0,4-1,5%).