IN TOUCH WITH NATURE

Otago Daily Times, Issue 21386, 14 July 1931, Page 2

IN TOUCH WITH NATURE

PLANTS ARE LIKE ANIMALS. By J. Drummond, F.L.S., F.Z.S. Some 20 years ago it was generally believed that the life-movements of plants were very different from the life-move-ments of creatures, that is, of all animals, meaning all animal life, to use the word in the wide sense in which it is used by biologists. When Sir Jagadis Chunder Bose, founder and director of the Bose Research Institute, Calcutta, announced that the remarkable movements of the sensitive plant, Mimosa, which inspired Shelley in the realms of poetry, are accompanied by signs that characterise the contraction of animals’ muscles, the announcement was received with incredulity. It was felt that his interpretations of the phenomena he had observed were opposed to the principles behind the actions and functions of plants. His latest work, “ The Motor Mechanism of Plants,” a copy of which has been sent by the publishers, shows beyond doubt that the sensitive plant reacts directly to stimulation in the same way as the muscles of animals react. Further than this, ordinary, non-sensi-tive plants respond to stimulation by movement which is not always perceptible, but which can be detected by sensitive apparatus with high magnification. The response is not limited to some plants, but is made by them all. Further still, he Ijas demonstrated that, just as in the body of an animal there is a rhythmic movement of internal organs concerned with the propulsion of food along the alimentary canal, so in the body of a plant there is a similar movement in a_ tissue that propels the sap. All experiments that affect the niovement of an animal’s heart or stomach affect in the same way the activity of the tissue that causes in the plant propulsion of the sap. There is a common factor in the mechanism that moves plants and animals. These experiments give the study of the life of the plant a higher significance and importance. Their author hopes that they will even point the way to a solution of many perplexing problems in the lives of animals.

The instruments demonstrate that Mimosa is hypersensitive to variations of light. Even a passing cloud induces a marked change. One leaf of a Mimosa plant showed signs of fatigue. Ozone gas introduced into the plant-chamber brought about an immediate change. Carbonic acid gas, on the other hand, has an asphyxiating action. Ether has a depressing effect on plants. The vapour of chloroform acts as a very strong narcotic. Any excess of its application is fatal. A large dose of chloroform not only produced a total abolition of excitability, but also caused a sudden spasm, the spasm of death. Mimosa is not uniformly sensitive. In one case, in the spring, the sensitiveness reached its maximum about mid-day, and remained constant for several hours. After that there was a continuous decrease, the minimum being reached about 8 a.m. the following day, when the plant was practically insensitive.

The symptoms of death in plants such as drooping, withering, and discoloration do not manifest themselves at the moment of death, but much later. At the moment of death violent excitation is developed in the plant’s tissue. A fairly large number of experiments proved that the rhythmic mechanism in plants and in animals is essentially similar. There are drugs that cause arrest of the heart and drugs that revive its activity. The same drugs applied to the pulsating leaflets of plants produced parallel effects. The action of extracts, of some Indian plants on the pulsation of leaves led to the discovery of their action on the animal dieart.

One of the most delicate instruments used in the experiments is a high-magnifi-cation sphygmograph, which records pulsations of the sap. Instruments of different degrees of sensitiveness were devised. The first gives a magnification of from 1000 to 5000 times; the second carries it to 25,000 times; the third to 10,000,000 times. The third and highest magnification is necessary to obtain a record of the individual pulse-wave in the propulsion of sap. By these experiments it was proved that somewhere in the interior of the plant there is an active tissue the pulsation of which, on the principle of a pump, affects the propulsion of the sap, in the same way as the pulsation of the heart_ maintains the circulation of the blood in animals. The venom of a cobra permanently stops pulsation, causing the plnpt’s death. AH the results obtained show that the mechanism for the propulsion of sap in a plant is similar in principle to the mechanism for circulating blood in an animal. The author of this notable book has skilfully arranged his facts and conclusions. He has brought the plant and animal kingdoms closer together, showing that, in the field he has investigated, one great principle runs through both.

When travelling on the River Warrego, Central Queensland, 37 years ago, Mr H. Wright. Hatuma, Waipukurau, often fished for Murray cod, using frogs for bait. The frogs were provided by natives for a small remuneration, and always were pale and colourless, devoid of the usual green colour. Mr Wright one day went with the natives to discover where they caught the frogs. He was surprised to learn that they dug the frogs out ox the hard ground with sharp-pointed yam sticks. They explained that the frogs were left on the plains by the river in flood, and that when the waters dried up the frogs were left stranded, and burrowed into the wet sand, making recesses whose walls seemed to be puddled in order to make them watertight. The frogs,_ it was explained, remained there, waiting patiently for the next flood, which might come in one year or in five or six years. The frogs that Mr Wright saw dug up had been in the ground for about a year, as during that time no rain had fallen and there had been no flood.

Sir Balwin Spencer, who invfestigated the habits of burrowing frogs in Central Australia, stated that many of them, probably, perish if the drought is an exceptionally long one. Describing his experiences, he stated that, when the clay-pans and the water holes dry up, all animal life, apparently, has completely died out. All the polyzoa and rotifers and other lowly creatures have perished. Their eggs remain and those may be blown about by the strong winds that often prevail in the dry months, and they are ready to develop as soon as the water holes are filled again. It is different with the frogs. People who know where to look for them will find them hidden away. They go into the mud while it is soft. It becomes so hard that it can be broken only piece by piece, and there they remain imprisoned until released by the next heavy rain.

The most interesting member of the group of Australian burrowing frogs is the water-holing frog. As the pools begin to dry up, it fills itself with water. This in some way unknown passes through the walls of the alimentary canal, filling up the body cavity and swelling the frog until it looks like a email orange. _ In this condition it occupies a cavity just sufficiently large for its body, and. it simply goes to sleep. Some burrowing frogs in captivity were turned out of tins and soon were found snugly hidden in small chambers beneath the surface of the earth. Each frog, by puffing itself out. and by turning round and round, had pushed back the earth and had puddled the walls. At other times they burrowed with their feet.