Category Science

Why does the Kurinji flower only once in 12 years?

Before flowering, a plant must attain the ripe-to-flower condition. To attain this condition the plant must complete a period of vegetative growth. Attainment of this condition does not automatically lead to the initiation of flower primordial.

            Certain environmental condition must follow. Temperature and the duration of light and dark periods within the 24 hour cycle are the two important environmental factors that influence the initiation of flower primordial in a plant that has attained ripe-to-flower condition. The response of a plant to this aspect of light is called photoperiodism.

            When appropriate photo period is given to a plant that has attained the ripe-to-flower condition, this metabolism is altered. This results in the formation of flower stimulus, which may be a hormone (florigen).

            When this flower stimulus is translocated to the shoot apex, the vegetative shoot apex is transformed to reproductive shoot apex, which results in the initiation of flower primordium.

            In natural conditions, the period taken to attain the ripe-to-flower condition and the period taken to obtain appropriate photoperiod differ widely among different plant species. Kurinji (Strobilanthes kunthianus) needs a period of 12 years for having to be subjected to a cycle conducive to flowering.

 

What is terminator gene technology? How is it used to help our farmers?

 

 

 

     

      On March 3, 1998, a joint patent (US patent No: 5723765) has been granted to United States Department of Agriculture (USDA) and the Delta and Pine Land Company, Mississippi in the name of ‘Control of Plant Gene Expression’. Mr. Hope Shand, Research Director, Rural Advancement Foundation International (RAFI), christened it as ‘Terminator technology’ as the hybrid seeds containing it do not germinate after one generation.

            The terminator technology is an extremely complex technology in which two gene systems are brought together to stop the normal process of embryo development, leading to the failure of seed germination. The gene systems are: Gene System I (Gene A) and Gene System II (Gene B and C).

            The gene system I consist of a gene ‘A’ which produces the ribosome inactivating protein (RIP), which is lethal to the growing embryo. Gene ‘A’ is linked to a transistently active LEA Promoter, ‘PA’, through a blocking sequence. A recombinase specific excision sequence (LOX sequence) flanks the blocking sequence on either side.

            The gene system II consists of a gene B linked to a promoter, PB the gene B encodes for a recombinase which is specific to the LOX sequence of the gene system I. A third gene C produces a repressor protein which blinds to the promoter PB and prevents the expression of gene B. The gene B can be depressed by exogenous application of tetracycline.

            To develop a variety of seeds with functional terminator system, two cells of the same crop are transferred with the gene system I and II separately. As a result, one transgenic is obtained with unexpressed gene A due to the presence of blocking sequence between gene A and its promoter PA and another transgenic is obtained with gene system II having repressor of gene B. To recombine these two systems into one, the obtained transgenic are hybridized and normal hybrid seeds are obtained. Since the gene A does not express, the seeds obtained remain viable. Upon treatment of the seeds with tetracycline, the antibiotic is absorbed by the seeding tissue. Since tetracycline acts as an inducer of gene B, it depresses the gene and recombinase is produced. The recombinase removes the intervening blocking sequence between gene A and its promoter PA. Thus PA comes in proper orientation with gene A and the gene ready for expression. The promoter specifically expresses during early embryo development. As a result, the seeds germinate normally in that generation and give rise to normal crop and seeds. But the seeds obtained do not germinate as the embryo gets aborted due to expression of gene A. so long as gene B remains repressed in absence of tetracycline, gene A is not expressed leading to production of viable seed.

            There are reports that this technology is presently being incorporated into two crops viz., tobacco and cotton. But it is a matter of time that it can be incorporated into other crops as well. This technology is not yet introduced into our country.

            It is premature to predict its impact on our farmers. However, we can visualize its utility in curbing the spurious practice of selling F2 seeds of a hybrid variety as F1 seed.

 

Could you ever see an eclipse of the Moon in daylight?

Yes, though only for a few minutes, and only if the eclipse is occurring just as the Moon is rising and the Sun is setting, or the Moon is setting and the Sun rising. A total eclipse occurs when the Earth is between the Moon and Sun, which are directly opposite to each other in the sky.

 Seeing both the Sun and eclipsed Moon at the same time would appear to be a geometrical impossibility, but because the atmosphere has a lensing effect, it raises the images of both the rising Moon and setting Sun above the horizon for a few minutes.

For the same reason, day and night are not exactly equal at the time of the fall equinox, because the day is artificially lengthened a few minutes at each end by the refractive effect of the atmosphere, for a total of seven minutes. It is not until three or four days later that the day equals the night.

It is easier to see the scallop of a partial eclipse above the horizon at sunrise or sunset than it is to see a total eclipse, because the Sun is so much brighter than the Moon.

       

With what materials are Saturn’s rings made of?

The rings around Saturn were first identified by astronomer Galileo Galilei in 1610. It was, however, Dutch Physicist Christian Huygens, who in 1659, recognized them as a broad, flat, thin ring, separated from the body of the plant.

In 1675, the Italian Astronomer G.D. Cassini identified two rings around it. Until 1969, it was believed that there were just three rings around Saturn “A”, “B”, and “C” and 151; “A” being the outermost and “C”, close to the planet. In 1969, the fourth ring was discovered by Pierre Guoria and soon, another one was also identified.

Pioneer satellite Data (1971) had indicated that was one more ring (“F”). French Astronomer, Edourd Albert Roche in 1849 postulated that the rings were the remnants of satellite that strayed too close to Saturn and due to which reason, disintegrated. His theory was that, if a satellite approaches, it’s primary, closer than a certain distance (known as “Roche Limit’ & 151; 2.44 times the radius of the planet), the satellite would break up and the broken pieces would gradually get distributed around the planet in a circular path.

The distances of the rings of Saturn are within the “Roche limit”. This would suggest that the rings are the remnants of a disintegrated satellite only.

The present thinking is that the rings are made up of countless small objects (varying in size from very small grains to small chunks of rocky material, covered by ice) and that each revolves around Saturn in its own orbit like a satellite.

That the rings contain particulate matter has been confirmed by  the fact that Rings “A” and “C” exhibit certain transparency due to which, the body of Saturn could he seen through them, as also the light from the stars.

 Furthermore, the satellites of Saturn are not completely eclipsed too, when they pass into the shadow of the rings. Very little information is available as to the precise composition of the matter in the rings. As per the observations of C.P. Kupier (1952), the Infra Red Spectrum is similar to the reflection spectrum of hoar-frost.

It is quite likely that these particles must have been of much bigger size earlier (even some metres in diameter), but these might have been a continuous reduction in their sizes due to their abrasion with objects like the meteoroids. Scientists are of the view that the continuous erosion may ultimately (at a far distant future) result in the rings slowly vanishing forever!

Why does the Moon look silvery at night?

 

 

 

 

 

 

 

 

 

 

The overall appearance of the Moon is bright ash grey caused by the dark and bright barren rocky land, where there is no atmosphere. When viewed in a naked eye or through a telescope, there are vast basins called seas, which were filled with molten lava millions of years ago. These are the low land plains appearing dark or dusky for the naked eyes. During the final ending phase of volcanism on the Moon, numerous crators had liberated enormous quantity of glowing gases and mineral vapours through their vents, which had blown in all directions over the surface, depositing the mineral condensates in the form of micron-size glassy spherules, tear drops and other powdery forms.

The Lunar surface is full of these bright rays like deposits, which scatter-reflect the sunlight quite effectively giving it a bright appearance on surface. The combined effect of rocks and soil along with the crators and minerals like calcium, aluminum and titanium therefore give a silvery appearance to the naked eye.

Why do we always see only one side of the Moon?

 

 

 

 

 

 

 

 

 

The Moon revolves around the Earth in a period of about 27 days; it also rotates once on its axis in the same time and so it always keeps the same face towards the Earth. This phenomenon is known as captured rotation.

Inspite of the fact that the Moon’s axial rotation is equal to its period of revolution round the Earth, we can actually examine more than the half of the total surface. The reason is that Moon travels round the Earth in an ellipse, not in a circle since it takes elliptical path, the rate of axial spin remains constant, whereas orbital velocity changes and moves fastest when closest to us.

We can thus see a little round alternate edges of the Moon. Also, the lunar orbit is tilted with reference to ours, so that the Moon is sometimes north and sometimes south of the mean plane, enabling us see some way beyond alternate poles. These minor shifts, known as Librations, allow us to examine four-sevenths of the total surface. The remaining three-sevenths of the Moon is permanently hidden from our inquiring eyes.

The time taken for the moon to turn on its axis once and the time taken for it to revolve once around the earth are the same. Hence the moon shows us the same face every night. This is called synchronisis rotation or captured rotation.