Which technique is employed for the extraction and elimination of hormones?

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?

If a plant needs $10$ hours of darkness to flower,identify the condition under which it will flower:
$I.$ $14$ hours day period
$II.$ $10$ hours dark period
$III.$ $9 \frac{1}{2}$ hours dark period
$IV.$ $9$ hours dark period
Choose the correct option:

The term "photoperiodism" was proposed by, or the phenomenon of photoperiodism in plants was discovered by:

The pigment phytochrome is involved in:

$A$ hypothetical 'florigen' could be produced prematurely in a long-day plant by exposing it to: