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Heliotropism, a form of tropism, is the diurnal or seasonal motion of plant parts (flowers or leaves) in response to the direction of the Sun. The habit of some plants to move in the direction of the Sun, a form of tropism, was already known by the Ancient Greeks. They named one of those plants after that property Heliotropium, meaning "sun turn".
The precise physiological mechanism enabling plant thermotropism is not yet understood. [4] It has been noted that one of the earliest physiological responses by plants to cooling is an influx of calcium ions from the cell walls into the cytosol, which increases calcium ion concentration in the intracellular space.
Sunflowers do not always point to the Sun. Flowering sunflowers face a fixed direction (often east) all day long, but do not necessarily face the Sun. [123] However, in an earlier developmental stage, before the appearance of flower heads, the immature buds do track the Sun (a phenomenon called heliotropism). Mature flowers face east. [124]
Some plants will even reduce the germination rate of other plants by 50%. [33] Current research is focused on the effects of weeds on crops, crops on weeds, and crops on crops. [ 38 ] [ 39 ] This research furthers the possibility of using allelochemicals as growth regulators and natural herbicides , to promote sustainable agriculture. [ 40 ]
Sunflowers do not have a pulvinus below their inflorescence. A pulvinus is a flexible segment in the leaf stalks (petiole) of some plant species and functions as a 'joint'. It effectuates leaf motion due to reversible changes in turgor pressure which occurs without growth. The sensitive plant's closing leaves are a good example of reversible ...
The Second World War was unleashed by the forces of imperialism, which also had racism in its arsenal. — Olga Lepeshinskaya Perhaps the only opponents of Lysenkoism during Stalin's lifetime to escape liquidation were from the small community of Soviet nuclear physicists : according to Tony Judt , "it is significant that Stalin left his ...
Commercially important plants in the Heliantheae include sunflower and Jerusalem artichoke. Many garden flowers are also in this group, such as Coreopsis, Cosmos, Echinacea, Rudbeckia, and Zinnia. Some authors separate Coreopsis and Cosmos into the Coreopsideae tribe. [1] In contrast to the benefits brought by the group, some are problematic weeds.
Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. [1]