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Bioelectromagnetism

FIGURE 5.5 Geomagnetic feld reversals and angiosperm evolution. In the direct comparison of GMF polarity

and diversion of angiosperms it is interesting to note that most of the diversion occurred during periods of normal

magnetic polarity. (From Mafei (2014).)

GMF. Tis was caused by a delay in fowering of plants in NNMF, which resulted in a signifcant

reduction in the harvest index of plants in NNMF compared with that of control plants. Terefore,

the removal of the local GMF negatively afects the reproductive growth of A. thaliana, which thus

afects the yield and harvest index (Xu et al., 2013). Since timing of fowering is crucial to the life cycle

of plants, it is not surprising that plants constantly monitor environmental signals to adjust the timing

of the foral transition (Capovilla et al., 2015), but it is amazing that this is exquisitely sensitive to the

GMF. Plant fowering time is controlled by several genes, including circadian clock-associated genes

(Hara et al., 2014), genes involved both in the transition from the vegetative to the reproductive phase

(Gu et al., 2013) and in the precise control of fowering (Song et al., 2014), and microRNA regulation

(Spanudakis and Jackson, 2014; Hong and Jackson, 2015). Current models provide us with a basis on

which to address a number of fundamental issues for a better understanding of the molecular mecha­

nisms by which plants respond to environmental stimuli to control fowering time (Fornara et al.,

2010).

A. thaliana plants grown under NNMF show a signifcant and consistent downregulation of gene

expression in early induction times for CCA1, CO, FD, FKF1, FRI, FT, GA20ox1, GA20ox2, LFY, LHY,

TOC1, TSF, and WUS. AP1, GI, and STM were downregulated at later times, whereas a signifcant upreg­

ulation was found for FLC during early foral induction, but the gene was downregulated during later

stages of foral development. In the foral meristem, despite its repressing activity on fowering, FLC was

signifcantly downregulated and during early times of fowering, LFY, SVP, SDG26, and, particularly,

FD showed a signifcant upregulation, whereas AGL24 was signifcantly downregulated in early times

and upregulated during fowering. SOC1 regulation occurred only during late fowering, whereas LFY

downregulation occurred later. GA2ox1 and GA20ox1 were mildly downregulated in the early phase of

foral development, whereas a strong downregulation was observed for GA20ox2 during early fowering.