Explain the role of Cytokinins and Ethylene in growth and development of Heredity plants
Answers
Answer:
Cytokinins may growth of apical tissue and ethylene are gaseous harmony, and for the growth of fruits
Answer:
Leaf growth and development are affected by various environmental factors and endogenous hormonal signals . These processes are regulated by phytohormones, transcriptional regulators and mechanical properties of the tissue (Bar and Ori, 2014). The role of ethylene in the leaf growth and development has been confirmed physiologically using ethylene inhibitors, and genetically using ethylene-insensitive mutants or transgenic plants lacking the key enzymes of ethylene biosynthesis (Oh et al., 1997; Bleecker et al., 1998). It has been observed that ETHYLENE RESPONSE FACTOR5 (ERF5) and ERF6, in Arabidopsis, improve leaf growth to environmental challenges (Dubois et al., 2015). The response of leaf growth and development to ethylene depends on concentration and species involved in the study (Fiorani et al., 2002; Kawa-Miszczak et al., 2003; Khan, 2005). In support of this, Fiorani et al. (2002) showed that the slower growing species of Poa (Poa alpina and Poa compressa) were more responsive to ethylene, with greater inhibition in leaf elongation than the fast growing species. However, a promoting effect on leaf elongation rate at a low ethylene concentration was observed in the slower growing species, while at the same concentration, leaf elongation rate was only slightly inhibited in the two fast-growing species. This response was reversed at higher concentrations, showing an inhibition effect. The study of Khan (2005) on mustard suggested that there exists a correlation between ethylene and growth of plants following the defoliation of mature leaves. Furthermore, ethylene-insensitive genotypes of Arabidopsis (Arabidopsis thaliana), tobacco (Nicotiana tabacum) and petunia (Petunia x hybrid) showed no increase in the total leaf area when compared to normal ethylene-sensitive control plants (Tholen et al., 2004). Treatment with ethephon, a compound that releases ethylene, resulted in an increase in both ethylene biosynthesis and leaf area expansion (Khan, 2005; Khan et al., 2008). In contrast, Voisin et al. (2006) determined that the rate of ethylene evolution had no relation to the leaf elongation rate variability in maize (Zea mays). Ethylene-induced reductions in leaf growth have been reported in pea (Pisum sativum) plants, around which rhizobacteria with enhanced ACC deaminase activity were added to soil (Belimov et al., 2009). Interestingly, the lower leaf area was observed in lettuce (Lactuca sativa) grown in closed environments, where ethylene produced from the plants reached stressful levels. The plants showed lower relative leaf growth rates compared to those grown in containers from which the ethylene had been scrubbed (He et al., 2009). This reduced leaf area was an indirect effect of ethylene on the leaf epinasty with reduced light capture, and/or on a reduced CO2 assimilation, which was found to be more sensitive to the ethylene increase than the reduction in growth. Both reactive oxygen species (ROS) and nitric oxide (NO), which could be potentially up-regulated by ethylene, have also been involved in leaf expansion
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