How does light affect plant growth?
Answer : Light energy is harnessed by plants to manufacture simple sugars through a process called photosynthesis. Therefore, plants require light for growth. The intensity of light required by different plants varies. Shade tolerant plants can survive at a lower intensity.
Is it true that a caterpillar only eats the leaves of the tree on which it was borned? Will the caterpillar eat grass if there are no other plants around? Do we classify a caterpillar as an insect?
Answer 1: It is true that caterpillars that hatch from eggs laid on a particular plant
will eat the leaves (or other plant parts, depening on the species) of that plant. Some caterpillars eat a variety
of plants within the same family of plants. If grass is related to the host plant of the particular species of
caterpillar, then it may eat it. Otherwise, it would not.
The caterpillar is the young of the butterfly or moth and therefore is an insect.
Answer 2: Caterpillar is just the larvae or young of an insect.
They normally feed on the leaves of the species of plant they were laid on. But, there are a few species which
hatch on one and move to another for feeding. Caterpillars of one species are usually very fussy about wbat they
eat. They are not general plant eaters. One species of caterpillar will normally feed on one species of plant,
or plants which are closely related to each other!
Answer 3: Usually the butterfly will lay the egg on the correct food plant for the
soon to be emerged caterpillar to feed on. There will only be a small set of plants that the caterpillar finds
suitable for eating, and grass will not do. For example, a number of the swallowtail family of butterfiles feed
on citrus plants.
Yes, a caterpillar is the larval form of the insect. It will metamorphose into a butterfly or moth.
What will happen to the animal (eg. dog), if I were to implant the nucleus of a plant cell, to its cell. Is there a possibility that the dog will turn into a plant? Why?
Answer 1: No the dog will not turn into a plant, because a plant
nucleus will not be able to function in a dog cell. The plant nucleus will need various special proteins for it
to carry out its function, and such an environment will not be available in a dog cell. When it comes to the time
for cell division, the plant nucleus is also unlikely to adjust to the timing for dog nucleus division, so will
be unable to form new daughter cells from which organisms grow.
Answer 2: The cell would probably die. The machinery to read the genetic code in the
transplanted nucleus would not be there. Replication of the DNA, along with its transcription and translation would
not occur as plants and animals are from different Kingdoms and the divergence of genes and proteins are pretty
high.
Answer 3: In order for a foreign nucleus (plant) to operate in a host (dog cell), the
dog cell must have the appropriate activators of the foreign genes (one of the factors among many), before the
(plant) genes can express. In your proposed scenario, it is not possible because dog and plant are not compatible.
Another wrong assumption is that all cells have the ability to lop into a new individual. While most if not all
plant cells are totipotent (I.e., given the right condition, cells from say a leave, can be transformed into a
new plant), most animal cells are not totipotent, except eggs and some embryonic stem cells. As far as animal cloning
is concerned you need an egg to drive the development. The egg contains all the mechanisms to activate the genes
in a nucleus, even if it is transplanted. But the nucleus must be of the same species in most cases.
Why do taxi drivers in Singapore put pandan leaves in their cars?
Answer : People believe that pandan leaves could keep cockroaches and houseflies away.
Long before the development of synthetic organic insecticides, natural substances derived
from plants were successfully employed in pest control. Many plants containing insecticides are known but very
few are cultivated. Many of them have been used for some time. Certain household sprays contain natural substances
from plants such as the pyrethrin of certain chrysanthemums, combined with other agents that are innocuous to man
and domestic animals.
The following are some of the observed effects of plant chemicals on pests and insects:
An article entitled "Natural Insect Deterrent" can be found in "Singapore Scientist" No. 81 (1997) pp 22-23. Try out some of the suggested experiments to see whether pandan leaves are effective in keeping insects away.
Please tell me more about carnivorous plants.
Answer : Carnivorous plants are green plants that obtain supplementary nutrition by
the active or passive trapping of animals, digesting their tissues and absorbing the breakdown products. For more
information, please refer to the following publication published by the Singapore Science Centre:
|
A Guide to the Carnivorous
Plants of Singapore |
Without light for photosynthesis, what gases are used and produced by plants at night?
Answer : In order to grow, plants require only light, water, carbon dioxide, oxygen,
and certain minerals. The minerals required by plants are absorbed by roots from the soil. After being dissolved
in water, they are transported from the roots to the leaves in vascular tissue that is continuous throughout the
body of the plant. Water carried to the leaves is needed for photosynthesis, although much is lost to evaporation
through the stomata. The carbon dioxide required for photosynthesis enters a leaf through the stomata.
We do not usually think that plants need oxygen, because it is available to them as a by-product of photosynthesis. However, plants do occasionally need to take in oxygen through the stomata and by root hairs from small pockets of oxygen in the soil. Because roots do not photosynthesize, this is their only supply of oxygen. Oxygen is needed for plant cell to carry on cellular respiration, a process that makes ATP available to them.
What are the effects of phosphates on the environment?
Answer: Rivers, streams, and lakes contain many organic and inorganic nutrients needed by the plants and animals that live in them. In higher than normal concentrations they become pollutants. Whereas organic nutrients nourish bacteria, certain inorganic nutrients stimulate the growth of aquatic plants. These include nitrogen, phosphorus, iron, sulphur, sodium and potassium. Nitrogen, in the form of ammonia and nitrates, and phosphorus, in the form of phosphates, are often limiting factors for populations of algae and other plants. Consequently, if levels become high, plant growth can go wild, choking lakes and rivers with thick mats of algae or dense growth of aquatic plants. In autumn, most of these plants die and are degraded by aerobic bacteria, which can deplete dissolved oxygen, killing aquatic organisms. As oxygen levels drop, anaerobic bacteria resume the breakdown and produces noxious products. The phosphate standard to prevent the growth of nuisance plants is 0.1 milligram per litre of water.
Can we grow grapes in Singapore? I heard that it can be done via hydrophonics; how true is that and how can it be done?
Answer 1: Yes, it is possible to grow grapes in Singapore via hydroponic culture. This
was done some years ago by the Primary Production Department. The bunches of grapes were sizeable too. However,
they were not sweet. This was expected because the sugar formation and accumulation in grapes is very much affected
by day length and environmental temperature. The tropical day length is just not long enough and temperatures not
appropriate.
Answer 2: Yes, we can grow grape plants in Singapore provided that the conditions given
are suitable. There were newspaper reports that people grew grape plants in their gardens but if you have better
facilities such as growth chambers and you manage the disease problems carefully, grape plants should be able to
grow. In fact, many temperate plants can be germinated from seeds and grow to certain extend in Singapore. I know
someone grow an apple tree in his garden. However, growing the plant is one thing, making the plant flowers and
fruits is another thing. Many temperate plants may grow here but may need special treatments such as colder temperature
or short-day conditions to trigger the flowering process.
Hydroponics is just one way of growing plants. Theoretically most plants should be able to grow hydroponically. Again this depends on how good your technique is.
If I implant the cells of one plant into another plant, will the plant bloom many different kind of flowers and bear different fruits? Why or Why not?
Answer : For the most part, NO. The cells of one plant are normally not compatible
with the cells of another, and will not be able to coordinate their activities to function as a whole organism.
For example, the times at which the cells of one species divides may be totally different from the one you are
trying to fuse it with.
However, gardeners have produced a lot of strange fusions in the past. Some of these are CHIMAERAs which were produced by grafting one stock against another. By accident, the cells may have been very compatible, and the plant produces two different types of flowers. The two species are likely to be closely related however.
How are flowers used as chemical indicators?
Answer :
Most plants contain many pigments and they occur most prevalently as glycosides. The anthocyanins are the most important and widespread group of colouring matters in plants. These water-soluble pigments account for many of the red, pink, purple, and blue colours found in higher plants. Plant pigments can be extracted with the right solvents at appropriate temperatures. Their colours are normally pH dependent and most plant pigments change colours with pH. Hence they can be used as acid-base indicators.
For additional information, please refer to the URLs bellow:
http://www.sci-ctr.edu.sg/ScienceNet/cat_physical/cat_che05052.html
http://www.sci-ctr.edu.sg/ScienceNet/cat_physical/cat_che06659.html
I heard that red cabbage can be used to fine the pH of a solution. Can you please tell me more?
Answer : Litmus is a pigment obtained from lichens and is used as an indicator to test
the acidic and alkaline nature of aqueous solutions.
Plant pigments can be extracted with the right solvents at appropriate temperatures.
Their colours are normally pH dependent and most plant pigments change colours with pH. Like universal indicators,
the extract obtained from red cabbage apparently composes of a mixture of component pigments which change colour
at different pH. It can be used effectively as a universal indicator. As the pH of the solution is changed from
1 to 14, the colour changes, following to the sequence below:
red -- pink -- purple -- blue -- green-- yellow
Relevant experiments using red cabbage extract as a universal indicator can be found
in the following book:
Chemistry Potpourri -- Unlocking Chemistry through Investigations
by Mabel Ho
Singapore Science Centre (1988)
Why do pH indicators change colour when they come into contact with acids or base?
Answer : Acid-base indicators are a special class of weak acids and bases in which
the ionised form has a different colour from the un-ionised form. Since small concentrations of these substances
will therefore change colour over a short pH range, by going from one colour form to the other as the pH changes,
they are of great utility for determination of the pH of solutions, or as indicators to show neutralisation of
an acid by a base, or vice versa.
Indicators may be either organic or inorganic. but by far the most useful and abundant
are the organic ones. The colour changes of organic indicators are distinctive and observable at low concentrations.
Some of them are bases (e.g. methyl violet, which is violet as the free base and yellow as the salt), while some
are acid (e.g. trinitrobenzene, which is colourless as the free acid but red-orange as the salt).
The basic indicators may be considered to be weak bases, subject to the equilibrium
Ind + H+ = IndH+ , while the acids undergo
IndH = Ind- + H+.
What is the difference between hydroponis and aeroponis?
Answer 1 : Both hydroponics (note: it is not spelt as hydroponis) and aeroponics are
techniques used to culture plants without using soil. Hydroponics, as the name suggests (hydro means water), use
liquid nutrient medium for plant cultivation. There are different variations of hydroponics cultures; a common
way is to grow plants in a container containing circulating nutrient solution. The root system of the plant is
submerged in the solution but not the shoot system.
For aeroponics, the root system is hanging in the air but keep moist by regular spraying
of droplets of liquid nutrient to the roots. A pump is normally employed for this purpose.
As both ways of growing plants do not use any soil, there are less plant pathogens
and thus less pesticides or fungicides are used. In addition, nutrient composition can be regulated and there is
better control of plant growth and development.
How do most aquatic plants propagate themselves? On which part of the water lettuce is the flower found?
Answer: Aquatic plants consist of several species in many different plant groups so
propagation is by means of all the various means available to plants; by spores, seeds, runners, buds, etc.
The flowers will develop on inflorescences which arise from the short stem which the leaves obscure.
Is water important for the growth of a plant?
Answer : Water is important for life. Each living thing, animal or
plant, consists of living cells. Each cell requires water for function in all its chemical processes, biological
regulations and transport of nutrients. The cell itself consists of at least 70% water. In the growth of plants,
each cell multiplies itself and more cells are formed. Without water, the plant will be unable to form new cells
and carry on normally with the chemical and biological processes.
Why do plants initially grow faster in dark than in light if they are planted on the same day with the same amount of water?
Answer :
I presume that your growth data were based on height measurement. In fact, plant growth can be measured in many different ways. For some kinds of experiments, a plant height measurement may suffice, but ordinarily more information is desirable. Individual leaf size; plant fresh weight and dry weight partitioned among organs, such as roots, stems, leaves, and fruits; cell numbers in tissues and organs; and concentrations of specific chemical constituents in tissues and organs are examples of growth data that need to be considered. During germination and emergence the seed food reserves are mobilised and transported to the embryonic plant, where they are first converted into root material. Root increase then levels off and the bulk of seed food reserves is diverted into leaf material. During the later phases of this period photosynthate from the growing leaves is available to support growth. With the establishment of enough leaf surface to support vigorous photosynthesis, further growth of roots, stems, and leaves would be accelerated.
Does a non-flowering plant bear seeds?
Answer : Flowering plants are the angiosperms and non-flowering plants are the rest of the plants, including gymnosperms, ferns, club mosses, whisk ferns, spike ferns, horsetails, hornworts, liverworts, mosses. The gymnosperms such as the pines, junipers, cycads, etc. can produce seeds so some non-flowering plants can produce seeds.
I am currently doing a project that require me to set up an aquatic ecosystem using water hyacinth. I would appreciate it if you could provide some information. Thank you.
Answer: Water hyacinth (Eichhornia Crassipes) is a free floating water plant that is native to South America. It can vary in size from a few
inches tall to over three feet. This plant has blue-green leaves, thick stalks and a showy purple or lavender flower.
It thrives in tropical regions and in waters that are high in nutrients. Water hyacinth is used in ornamental pools
and aquaria where it provides excellent cover for fish and the invertebrates upon which they feed. Cut flowers
are strikingly beautiful.
The main way water hyacinth reproduces is for a mother plant to send out a stalk which
grows a daughter plant, which matures and sends out another daughter plant, and so on. It is common to find several
generations among one stand of hyacinths, as the plants often remain entangled in a large mass. Hyacinths can also
reproduce through seed, but the seeds must germinate in very shallow, muddy areas. A seed dropped in relatively
deep water is unlikely to ever grow. Rarer still is the possibility of the hyacinth to regenerate from a plant
fragment. It may be able to do so, but it would take ideal conditions and several months for a whole plant to form.
Water hyacinth has one of the fastest growth rates of any plant known. Populations
can double in 12 days! It is a major pest weed in tropical and subtropical areas throughout the world. Water hyacinth
can completely cover lakes and rivers with more than 200 tons per acre. It blocks boat traffic, shades out submerged
plants, crowds out emergent plants and reduces oxygen in the water. It seriously depletes aquatic biodiversity
(including fish stocks) and affects water chemistry, and it harbours disease vectors (e.g. bilharzia snail vectors)
and snakes. Water hyacinth can be controlled using chemicals and by manual or mechanical removal. However, the
only sustainable solution to water hyacinth is biological control.
The URLs below provide additional information on water hyacinth:
http://www.agric.nsw.gov.au/ap/weeds/publications/p7643.htm
http://www.sidney.ars.usda.gov/scientists/nspencer/water_h/appendix6.htm
http://www1.surfsouth.com/~wilsonms/water.htm
http://www.gri.org/cgi-bin/re?url=http%3A//www.gri.org/pub/abstracts/gri80_0169.html
http://www.koivet.com/plants/hyacinth.htm
Why is auxin light-shy? Is it the only plant growth hormone?
Answer : I'm not personally aware whether the mechanism for auxin
moving away from a portion exposed to light is known, but we can speculate. Light is perceived by a set of compunds
known as photoreceptors eg phytochrome, which perceives red and far-red light, cryptochrome which perceives blue
light (and perhaps UV-A light) and an uncharacterised UV-B light receptor. Perception of light leads to the triggering
of signal transduction pathways within plant cells. The signal message passed on is likely to result in auxin accumulating
in shaded portions of the plant, through uncharacterised cellular transport phenomena, where it can then exert
its effect on growth and elongation of those cells.
4 other classically recognized plant hormones exist viz. cytokinin, gibberellin, abscisic
acid and ethylene (ethene). Other substances now recognized as plant hormones in that they cause changes in plant
growth and development include: carbon dioxide, jasmonic acid, salicylic acid, the brassinosteroids, systemin,
various oligosaccharides etc. etc. Each plant hormone may also have various active or inactive forms.
What is the difference between a monocotyledon and a dicotyledon plant?
Answer : Monocotyledon is a type of flowering plant that has one cotyledon (seed leaf). The leaves of these plants have parallel veins. The flower parts usually grow in multiples of three. Dicotyledon is a type of flowering plant that has two cotyledons (seed leaves). The cotyledons store reserve food for the embryo plant. Dicotyledon foliage leaves have netted veins. Their flower petals usually grow in multiples of 4 or 5.
I have been trying to grow cut pandan plants which I bought from the wet market. However they never survive. Please advise me the right way to grow this beautiful plant.
Answer :
There are many different types of Pandanus spp. Most of them can be found in the forest and some of them are coastal plants. The natural distribution of the genus extends from Africa and Madagascar, through S.E. Asia and Australia to the Pacific Islands. Some of the plants are shrubs and some can become small trees which can reach 6-8 m in height. The spiral arrangement of the long, toothed, narrow leaves give the plant their common name, the screw pine. Some of the species do not have toothed edge in their leaf margin.
Pandanus spp. are very adaptable plants, though they prefer hot, dry condition with good and indirect sunlight. The easiest method of propagation is by stem tip cutting or stem cutting, which root readily when placed directly in the soil. Stem cutting must have at least three or more nodes, preferably with aerial roots, and then it can grow easily. Also, suckers which are produced from the base of mature plants can be removed with aerial roots and treated as cuttings.
Does music affect plant growth? If so, how?
Answer : Over the years, I have seen some interesting projects presented at Science
Fairs. One of them was set out to verify whether plants appreciate music. Experiments were carefully designed and
carried out. Results showed that young bean plants subjected to heavy metal music grew faster than those subjected
to soft classical music. Young bean plants that were isolated from any music did not grow as well. The results
were repeatable. The conclusion was that plants like heavy metal music.
I was very amused by the result. It puzzled me for some time. When I mentioned such
experimental results to a renowned biologist from UK, he said that one should get the same result using an electric
fan in place of the loud speaker with music. In fact plants in nature grow well and strong with mechanical agitation
such as wind and storm. Hence, one may do the right experiment and draw the wrong conclusion.
Other than the afore-mentioned case, I have not come across any convincing experiments showing that plant growth is affected by music.