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... This comparative study showed that the plant in the lab germinated to develop true leaves and to show chlorophyll pigments in the stem and leaves. The plant at home grew more rapidly than the lab plant, its stems were white, almost clear, only its leaves showed chlorophyll pigments, no true leaves developed and phototropism was promoted. ... The active form of pytochrome, Pfr, and the inactive form, Pr, are the effects of photomorphogenesis. The active form absorbs red light which inhibits stem elongation while the inactive form absorbs far red light and causes stems to elongate rapidly. Elongation in the lab plant was slowed down more than the home plant. Being under 24 hour, continuous light, the active form of pytochrome absorbed red light and therefore, inhibited elongation. ... Plants that grow in the dark or under conditions of less than ideal light have been shown to have elongated stems, undifferentiated chloroplasts and expanded leaves. ... Plants grown under ideal lighting conditions, 24 hour continuous light, have an inhibition of elongated stems, accumulation of chlorophyll, differentiation of chlorophyll, and the expansion of leaves. ... (Audesirk 2002)
One of the main pigments in the development of stems is called phytochrome. ... Protochlorophyllide slows down chloroplast development and must be completely converted to chlorophyll before the chloroplast becomes functional. Light induces phototropism, photomorphogenesis, chloroplast differentiation and various other responses such as flowering and germination. ... Light is also the source of energy that regulates the form and color of the plants. Brassica plants growing under continuous light will be dark green with purple anthocyanin pigment strongly shown in the stem, leaves and flower buds. ... Their color will be less green and the purple anthocyanin color will be less intense also. Plants growing under less than sufficient light will have a very weak stem and will fall over more easily. ... Shoots are phototropic, meaning they grow towards the light while roots grow away from the light, showing negative phototropism. ... The auxin promotes the release hydrogen in the stem cells which results in the weakening of the cell walls. This induces turgor pressure and the cells elongate on the shady side of the stem. This bending towards the light is called phototropism. ...
Tools
A ruler was used to measure the growth of the stem and the size of the leaves. ... Its true leaves were seen in day 18 and measured to be about ½ cm in diameter. More true leaves grew from the stem and they all grew greater in diameter. There were a total of 5 true leaves that sprouted. ...
Table 1
Observation of the lab plant Observation of the home plants
Date length of hypocotyl (cm) Date length of hypocotyl (cm)
8/29 (planted seeds) 8/29 note: no true leaves developed during
the life of these plants
9/2 (day 4) no sprouting 8/30 (day 1) no growth
9/5 (day 5) just coming out of the soil, cotyledons can be seen
8/31 (day 2)
2 plants have sprouted through the soil
9/7 (day 9) 1 plant is 1/2 cm tall, cotyledons have formed 9/1 (day 3) both plants are approx. ... 4 cm
9/16 (day 18) still only one plant, 2-3/4 cm tall, true leaves have grown 9/6 (day 8) first plant: 3. ... 9 cm
9/19 (day 21) plant has grown to 3 cm tall,
leaves are growing bigger, cotyledons are growing 9/7 (day 9) first plant: 4. ... 5cm
9/23 (day 25) plant has grown to 4 3/4 cm tall, leaves are growing bigger,
cotyledons are growing, flower buds have appeared 9/9 (day 11) first plant: 6cm, second: 6. ... 2 cm
9/26 (day 28) buds have not opened yet, plant is 6 cm tall, 2 more
flower buds are growing on a true leaf 9/12 (day14) first and second are still on the edge - have not grown, third: 5.
Approximate Word count = 3208
Approximate Pages = 12.8
(250 words per page double spaced)
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