It was 10th May,1901.One Bengali Scientist was ruling the whole Royal Society at England. Acharya Jagadish Chandra Bose.He astonished the brilliant scientists of the world showing them that plants have life too.After his path breaking invention scientists got a new world on which they can start their new science.
It was every plant’s worst nightmare. In the fall of 2009, in a Victorian greenhouse at the Cruickshank Botanic Garden at the University of Aberdeen in Scotland, Zdenka Babikova covered vegetation-devouring aphids on eight broad bean plants and sealed each plant’s leaves and stems inside a clear plastic bag. Babikova, a PhD student at the University of Aberdeen, knew that aphid-infested bean plants release odorous chemicals known as volatile organic compounds (VOCs) into the air to warn their neighbors, which respond by emitting different VOCs that repel aphids and attract aphid-hunting wasps.She didn’t know that these plants also can have underground communication.After a very short time experiment she came to know that yes,these creation of nature are completely amazing!!Yes,they can talk to each other,they can help each other,they can communicate with their neighbors.After 100 years of JC Bose’ s invention world saw something different,something interesting about these green world.
Plants are exposed to various stress factors such as disease, injury, herbivory, extreme heat/cold, etc. Hence, they must adjust their physiological state either in response to, or in preparation for, such conditions to their well-being and survival. To achieve this adjustment, plants have developed a communication system to transmit information based on volatile organic compounds (VOCs).
The trigger for development in this field was the discovery that undamaged poplar and sugar maple trees accumulated phenolics and tannins when situated close to damaged trees.However, in this original report, no active principle was identified. Methyl jasmonate (MeJA) emitted by sagebrush (Artemisia tridentata) was the first compound shown resistant to herbivores by increasing the proteinase inhibitor production. Later other VOCs emitted by damaged plants were found to influence the receiver plants, regardless of whether or not the receivers were conspecies.
Now we will see how plants communicates in different ways,
Whispers on the wind
In 1983, plant scientists Jack Schultz and Ian Baldwin reported that intact maple tree saplings increase their defense systems when exposed to herbivore-damaged maples. The injured trees, they suggested, were alerting neighbors to the presence of a predator by releasing chemical signals into the air. But the plant research community didn’t buy it. After a decade in 2000, Karban showed that wild tobacco plants grown in close proximity to sagebrush plants whose leaves had been clipped became resistant to herbivores, in response to VOCs released by the sagebrush.Other researchers soon reported similar VOC-induced defense responses—both intra- and inter species—in several other plants. And in 2006, he showed that VOCs released by damaged sagebrush induce herbivore resistance in plants growing at distances of up to 60 cm, well within the range of sagebrush neighbors in nature.From then this became well explained and acceptable to the scientists.
Gas chromatography–mass spectroscopy (GC-MS) has been employed to identify a variety of induced plant VOCs. One major group is the terpenoids, with subgroups named after the carbon numbers. Although countless terpenoid species have been discovered, only a limited number are involved in plant communications. An equally major group is the green leaf volatiles (GLVs) generated from lipids. They are produced from C18 fatty acids, particularly linolenic acid, by the action of hydroperoxide lyases and the subsequent shift of the olefinic bond, reduction of the carbonyl group and esterification. The phytohormones MeSA and ethylene are also volatiles involved in defense. MeSA is emitted from the local infected region to induce systemic acquired resistance (SAR) in the emitter itself and receivers. Ethylene, which is known to enhance maturation of various fruits, particularly underlies plant disease response. Ethylene has also been found to amplify the defense response induced by (Z)-3-hexen-1-ol and amplify the emission of sesquiterpenes in Zea mays.
Plant gossip is not only spread on the breeze; the rhizosphere crackles with chatter, too. Over the past few years, a team led by Ariel Novoplansky of Ben-Gurion University of the Negev in Israel has produced compelling evidence that plants eavesdrop on hints of their neighbors’ distress through their root systems. Novoplansky’s team planted six garden pea plants so that each pot contained the roots of two different plants. The researchers then subjected the first plant in each row to drought-like conditions and evaluated the response of its neighbors by measuring the width of the microscopic pores, called stomata, on leaf surfaces, which close in response to drought stress. Fifteen minutes after drought was initiated, the stressed plant closed its stomata—as did its nearest unstressed neighbor, suggesting some sort of drought warning sign had been passed between the two. After an hour, all five neighbors, each more distant from the stressed plant—the only one that actually experienced drought-like conditions—had also shuttered their stomata, indicating that they, too, received the message to prepare for drought.
Importantly, in a control setup where root contact between neighboring plants was blocked, pores stayed open, indicating that the message was somehow being passed between roots.
Meanwhile, other researchers are starting to explore another underground plant communication system, one in which messages are sent through the labyrinth of hairlike fungal filaments .These mycorrhizal fungi are involved in an important mutualistic relationship: in exchange for sugars, they provide plants with much-needed phosphorus and nitrogen. In many cases, the fungi connect the roots of neighboring plants to form common mycelial networks (CMNs), which play a major role in recycling soil nutrients and water. CMNs may also carry signals over far greater distances than airborne volatiles can. One 2009 study documented a fungal network that wove its way through an entire forest, with each tree connected to dozens of others over distances as great as 20 meters.
Monica Gagliano’s first attempt to publish evidence suggesting that plants might communicate with each other using sounds was met with rank disbelief. Her manuscript was rejected by six different journals in 2010 and 2011. Gagliano kept plugging away. In April 2012, after she had repeated her experiments and it was accepted at last, the study showed that chili plant seedlings grown next to fennel germinated more quickly than seedlings grown with conspecifics. Gagliano and her colleagues suspect the chili plants are compensating for the presence of the fennel, which is known to release chemicals that inhibit the growth of other plants. Remarkably, however, all known interplant communication pathways—airborne volatiles, root contact, and common fungal networks—were blocked. Theoretically, she says, sound has several advantages over chemical signaling: it propagates faster and over greater distances, and it can be generated with fewer energy costs. But behavioral ecologist Carel ten Cate points out that taking advantage of such benefits would require sensory mechanisms yet to be described in plants. Plants do generate sounds at frequencies outside the range of human hearing, but it’s not clear how they are produced or whether plants can detect sounds at all.
So,aren’t these all too much interesting? Aren’t these all some how making us to recall that great Bengali Scientist who ruled over the rulers of his motherland 120 yeras back?
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BS-MS student, IISER Bhopal