Start of Autumn: White dew descends

February 13th, 2012
by Jo Law

The length of day has been steadily decreasing since the December solstice. The last ‘longest day of the year’ in the southern hemisphere was December 22nd, 2011. On that day in Wollongong, the sun rose at 05:39, set at 19:07 and gave us approximately 14 hours and 28 minutes of daylight. The current day length is around 13 hours and 23 minutes and will continue to decrease until the June solstice on the 20th of that month. On March 25th, 2012, it will be equilux in Wollongong when we will have 11 hours and 59 minutes of daylight and 12 hours and 1 minute of darkness.

Plants and animals display different degrees of photoperiodicity, or physiological reponse varying day length (and night). The amount of daylight provides information about the seasons to angiosperms or flowering plants. Long day plants flower as day length begins to exceed 12 hours while short day plants require longer period of darkness and typically flower in the short days of spring. Day netural plants flower (and set fruit) when they reach the appropriate developmental stage and, in part, in response to other environmental factors.

The lengthening of daylight in spring sends an important cue to male song birds, whose reproductive systems’ response to the gradual increase in light is outwardly expressed as an increase in musical outputs. This reproductive strategy takes advantage of the ample food supplies available in the season. By the same token, chickens respond to the shortening day length by reducing egg production and then stopping altogether in the coldest months. Our chickens have already taken the decrease in daylight as cue to reduce egg production and soon they will begin to moult…

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