Vergara - 1976 - Physiological and morphological adaptability of ri

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4. Distributions of parents and F; plants by the seeding-to-panicle initiation period in a
strongly sensitive - essentially insensitive cross when grown under a 10-hour phutoperiod (left)
and under natural day length at Los Bafios (right).
The Se gene or genes are epistatic to the Efgenes under a photoperiod longer
than the critical photoperiod. When infonnation is available concerning the
prevailing day length and the probable genotype of the parents with respect to
BVP and PS1’. much of the previous investigations on groxvth duration could be
readily reinterpreted and conflicting evidences resolved. The dominant and
cumulative nature of the Ef genes for BVP agreed ‘with the findings of many
previous investigations where earliness was dominant to lateness obtained under
natural day length in insensitive >< insensitive crosses (Ramiah. 1933; Yao and
Yu, 1963; Kuriyama, 1965; Dhulappanavar and Mensinkai, 1968; Heu and
Chae. 1968; Kudo, 1968'. Wu, 1968'. Li and Chang, 1970].
While the partitioning of the vegetative growth duration into BVP and PS1’
has greatly elucidated the genetic control of this variable trait. how to measure
precisely the quantitative nature of photoperiodic response under a changing
natural day length at different latitudes remains a challenging problem for plant
scientists. It has been demonstrated that the same F1 population produced
different patterns of segregations when plantings under natural day length and
controlled photoperiod were compared (Fig. 4) [Chang et al, 1969). There is
some indication that BVP could be affected by differences in temperature.
lEMPl-iRAlURE RESPONSE
Although the rice plant is primarily tropical in origin, it can survive a wide
range ofair temperatures ranging from 10° to 50°C (Sooinro and McLean, 1972).
The plant can also tolerate water temperatures ranging from 13° to 38°C.