Effect of phytohormones on chlorophyll degradation during aging of chloroplastsin vivo andin vitro

Nitric Oxide Signaling During Senescence and Programmed Cell Death in Leaves

“…Hence, leaf yellowing is regarded as an external symptom of programmed cell death processes in senescing leaf cells (Nooden et al, 1997;Hortensteiner and Matile, 2004). The first visible event during senescence is leaf yellowing (Misra and Biswal, 1980;Quirino et al, 2000). Photosynthesis gradually slows down (Dilnawaz et al, 2001;Misra et al, 2002;2010;2011a;2010;Misra and Biswal, 1982) and finally stops, but mitochondria and nucleus remain functional and respiration continues until the end of the senescence (Srivastava, 2002).…”

“…Plant hormones play an important roles in the regulation of the onset of senescence (Misra and Biswal 1980;Misra and Misra 1989a;. All the identified phytohormones are reported to be involved in leaf senescence.…”

“…Cytokinins play a master regulatory role in leaf senescence (Misra and Biswal, 1980). While increasing cytokinin production could delay leaf senescence (Gan and Amasino, 1995), reducing endogenous cytokinin levels resulted in accelerated senescence (Masferrer et al, 2002).…”

“…Many other stress-inducing conditions such as drought, darkness, high temperature, high light, ozone, and pathogen attack can hasten leaf senescence as well (Biswal et al, 2001;Misra et al, 2001a, b;Misra and Misra 1986a, b;Misra and Biswal 1980, 1981, 1982aLim and Nam, 2005).…”

“…Auxin, which regulates many aspects of plant growth and development, also influence leaf senescence, and is reported to delay leaf senescence (Misra and Biswal, 1980;Ellis et al, 2005).…”