scholarly journals Formation Mechanism and Anatomical Structure of the Knee Roots of Taxodium Ascendens

2021 ◽  
Author(s):  
Zhuangzhuang Qian ◽  
Lin Wu ◽  
Luozhong Tang
Keyword(s):  
Formation Mechanism ◽  
Root Formation ◽  
Developmental Stages ◽  
Scientific Evidence ◽  
Acc Synthase ◽  
Anatomical Structure ◽  
Endogenous Hormones ◽  
Intercellular Spaces ◽  
High Flood ◽  
Indole 3 Acetic Acid

Abstract Aims: Flooding seriously limits the growth and distribution of plants. Taxodium ascendens is a typical tree species with high flood tolerance, and it can generate knee roots in the wetlands. This study was conducted to understand the formation mechanism of the knee roots.Methods: The number and size of knee roots and soil flooding conditions were investigated in this study. Furthermore, physiology, biochemical responses, and the anatomical structure of knee roots and underground roots were measured at different developmental stages. Results: The results show that the formation of knee roots was significantly affected by the soil water table (P < 0.05). Moreover, knee root formation was affected by ethylene and indole-3-acetic acid (IAA) concentrations in the roots. The 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC synthase activity were significantly lower in the knee roots than in the underground roots. The ethylene release rate was significantly higher in the knee roots than in the underground roots (P < 0.05), and IAA content first increased and then decreased with knee root development. The cells of the periderm at the apex of the knee roots were dead and had a large number of intercellular spaces, which was beneficial for the growth of T. ascendens. Conclusions: Seasonal flooding induced the production of endogenous hormones, resulting in the formation of knee roots, which improved root respiration and ventilation. The results obtained can gain a basis for the formation mechanism of knee roots and provide scientific evidence for the afforestation and management under wetland conditions.

Two actions of juvenile hormone on the follicle cells of Rhodnius prolixus Stål

1975 ◽  
Vol 53 (8) ◽  
pp. 1187-1188 ◽  
Author(s):  
Randa Abu-Hakima ◽  
K. G. Davey
Keyword(s):  
Juvenile Hormone ◽  
Developmental Stages ◽  
Normal Animal ◽  
Rhodnius Prolixus ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Intercellular Spaces

The follicular epithelium of vitellogenic oocytes from allatectomized females of Rhodnius fails to develop large intercellular spaces when exposed to juvenile hormone (JH) in vitro. This suggests that in the normal animal, the follicle cells require JH at two developmental stages. Differentiation of the cells in the presence of JH represents one requirement, and only those cells which have undergone this initial priming are fully competent to exhibit the second response, the development of intercellular spaces.

scholarly journals Effects of light and ethylene on endogenous hormones and development of Catasetum fimbriatum (Orchidaceae)

2006 ◽  
Vol 18 (3) ◽  
pp. 359-365 ◽  
Author(s):  
Rogério M. Suzuki ◽  
Gilberto B. Kerbauy
Keyword(s):  
Leaf Growth ◽  
Shoot Elongation ◽  
Zeatin Riboside ◽  
Endogenous Hormones ◽  
Light Conditions ◽  
Active Growth ◽  
Dark Light ◽  
The Difference ◽  
Catasetum Fimbriatum ◽  
Indole 3 Acetic Acid

This study attempted to clarify the effects of dark, light and ethylene on plant growth and endogenous levels of indole-3-acetic acid (IAA), cytokinins and abscisic acid in Catasetum fimbriatum. Dark-incubation fully inhibited root and pseudobulb formation as well as leaf growth, but favored shoot elongation. The results of continuous and active growth in dark-incubated shoots (stolons) were induced by strong apical meristem sink activity and by the significantly increased levels of cytokinins in shoots. In fact, shoot length, cytokinin and IAA levels in dark-incubated shoots were about twice as great as for those grown under light conditions. Moreover, the total cytokinin level in shoots of C. fimbriatum under light conditions without ethylene was significantly higher than that found in roots. High levels of cytokinins in dark-grown stolons may be closely related to the absence of roots in C. fimbriatum. Under light conditions, the increased IAA level in shoots is mediated by ethylene. However, ethylene caused a significant increase of cytokinins in roots of light-treated plants, which may be involved in the retardation of root growth. Since the difference of cytokinins in shoots between ethylene-treated and non-treated plants under light conditions is small, it is concluded that the marked inhibition of leaf growth in ethylene-treated plants can be attributed to ethylene. Zeatin and zeatin riboside are the major cytokinins in C. fimbriatum regardless of the light conditions, ethylene treatment or organ types.

scholarly journals Multiple AUX/IAA–ARF modules regulate lateral root formation: the role of Arabidopsis SHY2/IAA3-mediated auxin signalling

2012 ◽  
Vol 367 (1595) ◽  
pp. 1461-1468 ◽  
Author(s):  
Tatsuaki Goh ◽  
Hiroyuki Kasahara ◽  
Tetsuro Mimura ◽  
Yuji Kamiya ◽  
Hidehiro Fukaki
Keyword(s):  
Lateral Root ◽  
Target Gene ◽  
Root Formation ◽  
Auxin Response ◽  
Cell Specification ◽  
Asymmetric Cell Divisions ◽  
Auxin Signalling ◽  
Lateral Organ ◽  
Indole 3 Acetic Acid

In Arabidopsis thaliana , lateral root (LR) formation is regulated by multiple auxin/indole-3-acetic acid (Aux/IAA)–AUXIN RESPONSE FACTOR (ARF) modules: (i) the IAA28–ARFs module regulates LR founder cell specification; (ii) the SOLITARY-ROOT (SLR)/IAA14–ARF7–ARF19 module regulates nuclear migration and asymmetric cell divisions of the LR founder cells for LR initiation; and (iii) the BODENLOS/IAA12–MONOPTEROS/ARF5 module also regulates LR initiation and organogenesis. The number of Aux/IAA–ARF modules involved in LR formation remains unknown. In this study, we isolated the shy2-101 mutant, a gain-of-function allele of short hypocotyl2/suppressor of hy2 ( shy2 ) /iaa3 in the Columbia accession. We demonstrated that the shy2-101 mutation not only strongly inhibits LR primordium development and emergence but also significantly increases the number of LR initiation sites with the activation of LATERAL ORGAN BOUNDARIES-DOMAIN16/ASYMMETRIC LEAVES2-LIKE18 , a target gene of the SLR/IAA14–ARF7–ARF19 module. Genetic analysis revealed that enhanced LR initiation in shy2-101 depended on the SLR/IAA14–ARF7–ARF19 module. We also showed that the shy2 roots contain higher levels of endogenous IAA. These observations indicate that the SHY2/IAA3–ARF-signalling module regulates not only LR primordium development and emergence after SLR/IAA14–ARF7–ARF19 module-dependent LR initiation but also inhibits LR initiation by affecting auxin homeostasis, suggesting that multiple Aux/IAA–ARF modules cooperatively regulate the developmental steps during LR formation.

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