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christchurch, New Zealand

my giant sunflowers are growing very fast and i was checking their daily growth but found that they actually shrink during the day as much as 2 cm and then sprout during the night as much as 6 cm
the weather is hot and today was damp and 18 c
water on it is same all day the ground is well dampened so not lack of water during the day
so this is a mystery to me

On plant giant sunflowers shrinking in day growing at night



Interesting? You should write a blog on this perhaps?

11 Jan, 2010


this will be due to turgour. during the day they lose water due to transpiration being higher. the small openings on the leaf that lets gases in and out during photosynthesis also lets water out. during the night these openings are almost closed so less water is lost. [eg a 5cm potato chip will gain 2 - 3 mm in length when left in water.] The cells get full of water and swell pushing the cellwall out as far as possible. when rows of hundreds of cells do this the resulting 'growth is measureable.

hope this makes sense.

11 Jan, 2010


wow thank you.
i have been measuring daily the growth
it easy with such a huge plant and just measured it now and over night it grew 100 mm.(now 2.6 meters and just a teenager)
so growth in actual height and growth seems to depend on a lot of factors.

i once used privet hedge cuttings(just the tender tips) for compost and planted cabbages in the area and one of the cabbages was so big it dwarfed my 2 year old son sitting beside it and i recon it was the 'gibberaldic acid ? ' in the fast growing tips of the hedge that did it.

might try and keep it wet with a hose during the day and see if that makes a difference in actual average growth
however it would seem the opening of the cells for using the sun is the determining factor as one day it grew a bit but it was a dull day i think
was able to google the word above and now have the seed of info to find out more

12 Jan, 2010


Hello, sorry not replied soon but I have had a glitch on the site.
the openings are called stomata and the cells responsible for opening and closing are called stomatal guard cells. The way they work is facinating and all down to water potential in the cell. on windy days plants often wilt even though there is water available in the soil. this is known as physiological drought. the plant loses water by transpiration faster than the roots can absorb it. over night the plant gains enough water so next day it is back to normal.

please ask for mor info if you'd like it. :o)

14 Jan, 2010


the info here has opened an interesting subject for me yesterday it was raining and it grew a little but not overnight.

14 Jan, 2010

How do I say thanks?

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