(and possibly jasmonic and salicylic acid in addition). This causes even more ABA and strigolactones to be made until the leaf is drained of all nutrients. When conditions get particularly bad in the emptying mature leaf cell, it will experience sugar and oxygen deficiencies and so lead to gibberellin and finally ethylene emanation. When the leaf senses ethylene it knows its time to excise. Root pruning – the concept that plants prune the roots in the same kind of way as they abscise leaves, is not a well discussed topic among plant scientists, although the phenomena undoubtedly exists. If gibberellin, brassinosteroid and ethylene are known to inhibit root growth it takes just a little imagination to assume they perform the same role as ethylene does in the shoot, that is to prune the roots too. Hormonal root pruning theory – in the new theory just like ethylene, GA, BA and Eth are seen both to be induced by sugar (GA/BA) and oxygen (ETH) shortages (as well as maybe excess levels of carbon dioxide for Eth) in the roots, and to push sugar and oxygen, as well as minerals, water and the growth hormones out of the root cell causing a positive feedback loop resulting in the emptying and death of the root cell. The final death knell for a root might be strigolactone or most probably ABA as these are indicators of substances that should be abundant in the root and if they cannot even support themselves with these nutrients then they should be senesced. Parallels to cell division – the theory, perhaps even more controversially, asserts that just as both auxin and cytokinin seem to be needed before a plant cell divides, in the same way perhaps ethylene and GA/BA (and ABA and strigolactones) are needed before a cell would senesce. Seed senescence Seed germination performance is a major determinant of crop yield. Deterioration of seed quality with age is associated with accumulation of DNA damage. In dry, aging rye seeds, DNA damages occur with loss of viability of embryos. Dry seeds of Vicia faba accumulate DNA damage with time in storage, and undergo DNA repair upon germination. In Arabidopsis, a DNA ligase is employed in repair of DNA single- and double-strand breaks during seed germination and this ligase is an important determinant of seed longevity. In eukaryotes, the cellular repair response to DNA damage is orchestrated, in part,