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Lateral Organs (lateral + organ)
Selected AbstractsThe Arabidopsis ARGOS-LIKE gene regulates cell expansion during organ growthTHE PLANT JOURNAL, Issue 1 2006Yuxin Hu Summary Cell expansion, and its coordination with cell division, plays a critical role in the growth and development of plant organs. However, the genes controlling cell expansion during organogenesis are largely unknown. Here, we demonstrate that a novel Arabidopsis gene, ARGOS-LIKE (ARL), which has some sequence homology to the ARGOS gene, is involved in this process. Reduced expression or overexpression of ARL in Arabidopsis results in smaller or larger cotyledons and leaves as well as other lateral organs, respectively. Anatomical examination of cotyledons and leaves in ARL transgenic plants demonstrates that the alteration in size can be attributed to changes in cell size rather than cell number, indicating that ARL plays a role in cell expansion-dependent organ growth. ARL is upregulated by brassinosteroid (BR) and this induction is impaired in the BR-insensitive mutant bri1, but not in the BR-deficient mutant det2. Ectopic expression of ARL in bri1,119 partially restores cell growth in cotyledons and leaves. Our results suggest that ARL acts downstream of BRI1 and partially mediates BR-related cell expansion signals during organ growth. [source] Hamatophyton from the Late Devonian of Anhui Province, South China and Evolution of SphenophyllalesACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009Deming WANG Abstract: Well-preserved specimens of Hamatophyton verticillatum collected from the Upper Devonian (Famennian) Wutong Formation of Chaohu district, Anhui Province, South China, display more complete fertile axes in three orders and multiple divisions. Comparisons indicate that Hamatophyton possibly does not have palmate planate sterile leaves but hook-like linear ones with rare divisions. We propose seven definitive characters of Sphenophyllales: (1) completely whorled lateral organs; (2) sterile leaves; (3) strobili; (4) "sporangiophores" or stalks with reflexed tips bearing sporangia; (5) three- or four-ribbed primary xylem; (6) exarch maturation of primary xylem; and (7) secondary xylem. The Sphenophyllales probably originated from the Iridopteridales based on similarities in whorled lateral organs, ribbed primary xylem and peripheral protoxylem strands. In transition from Iridopteridales to Sphenophyllales, morphological changes involve partially whorled to completely whorled lateral organs, sterile ultimate appendages to leaves, and fertile ultimate appendages to "sporangiophores"/stalks with bracts; anatomical modifications include configuration and maturation of primary xylem, and presence of secondary xylem. [source] Structure of sperm, spermatozeugmata and ,lateral organs' in the bivalve Arthritica (Galeommatoidea: Leptonidae)ACTA ZOOLOGICA, Issue 1 2009Åse Jespersen Abstract The position and structure of paired ,lateral organs' in the foot of Arthritica semen and Arthritica bifurca might indicate a chemosensory function. In both species part of the organ is also glandular. In A. semen the glandular epithelium is detached piecemeal and, probably by means of the foot, is moved to and grafted upon the gills of the same individual. The transferred epithelia appear as disk-shaped actively secretory ,gill bodies' which, attached to the abfrontal side of the inner demibranch, replace the ordinary unciliated gill epithelium. The secretion is liberated into the suprabranchial chamber, which serves as a marsupium, but its function is uncertain. Arthritica semen is a protandric hermaphrodite and produces very large ova that undergo a direct development that results in a non-planktonic lecithotrophic crawling juvenile stage. The sperm cells have filiform nuclei that are straight in the euspermatozoa and more or less helicoidal in what is considered to represent paraspermatozoa. By a process of aggregation, spermatozeugmata are formed which consist exclusively either of euspermatozoa or paraspermatozoa. Spermatozoa are stored in the oviduct in A. semen but in paired seminal receptacles in A. bifurca. [source] | ||||||||||