07-01-2009, 11:39 PM
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#30 |
| Seedling
Join Date: Apr 2009
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Quote:
Originally Posted by knna  AS time ago we had a interesting disscusion about this topic at the Cannabis World (before it was converted on a seed sale site), im going to quote myself, includiong some very useful links (hope they still work):
"[color="red"]As i said before, RH measure alone is insufficient to inform about transpiration rate. | Thought you might be interested in this: Heat stress increases sensitivity of pollen, fruit and seed production in tomatoes (Lycopersicon esculentum Mill.) to non-optimal vapor pressure deficits. Quote: |
The optimum relative humidity for tomato pollination is generally thought to be 50-70%, but has not been well tested under controlled conditions or in combination with high temperatures. Starting two weeks before anthesis of the first flower, three tomato (Lycopersicon esculentum) cultivars, NC8288, FM-9 and FL7156, differing in heat tolerance were exposed to mild heat stress (31/25 vs. 28/22°C) at three relative humidity levels (30, 60 and 90%) in controlled environment chambers. These treatments represented vapour pressure deficits (VPD) ranging from 0.45 to 3.16 kPa during the day or 0.38 to 2.7 kPa averaged over a 24-h period. Pollen development in the anthers was followed cytologically, pollen release and germination were measured at anthesis, and seed production and fruit weight were measured in mature fruit. Fruit set, undeveloped flowers percentage, total fruit weight, and percentage pollen germination were most sensitive to high humidity (decreasing VPD) at high temperature, and were most sensitive to high temperature at high humidity. Over all, the optimum VPD was 2.25 kPa and plants grown at 28/22°C performed better than those grown at 31/25°C. Differences between cultivars in response to high humidity were less than those for temperature responses. Cytological examinations revealed pollen developmental anomalies in some, but not all, cultivars at 90 and 30% relative humidity.
| and this: SpringerLink - Journal Article
Last edited by LJB; 07-02-2009 at 10:30 AM..
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