What happens if winter-growing plant species are sown in the spring season?

Some varieties of wheat are known as spring wheat while others are called winter wheat. The former variety is sown and planted in spring and is harvested by the end of the same season. However,winter varieties,if planted in spring,fail to flower or produce mature grains within a span of a flowering season. Explain,why?

The relation of flowering to the lengths of light and dark periods was investigated by two experiments. In one experiment,the plants were subjected to dark periods of various lengths while the light periods were kept at $4$ hours. In the second experiment,plants were kept in dark periods of various lengths while the light periods were kept at $16$ hours. The number of flowers formed in relation to these periods is shown in the table. These results indicate that flowering:

Dark periods (hours)	Flowers formed (Light: $4$ hrs / $16$ hrs)
$8$	$0$ / $0$
$10$	$0$ / $0$
$12$	$4$ / $6$
$14$	$5$ / $7$
$16$	$5$ / $8$

Give scientific reasons:
$(1)$ Photoperiodism is essential for flowering in plants.
$(2)$ Abscission (leaf fall,flower fall,fruit fall) increases the vitality of plants.

Which of the following pigments is present in two forms?

The wavelength of light absorbed by the $P_r$ form of phytochrome is (in $nm$)