LIFE SCIENCE FOR GENERAL UNDERSTANDING: PLANTS

 LIFE SCIENCE FOR GENERAL UNDERSTANDING:      PLANTS

[ON REQUEST FROM Cdr. V. KRISHNAN]

A general belief is that plants have leaves, flowers, fruits and seeds. Each one of these components may be missing from some plants. So, generalizations may not always hold good. As for instance, we believe animals run. There are some which cannot. Eg: Sponges. Interestingly there are ‘walking ferns’ though they do not really ‘walk’. To be clear about these living systems, one has to begin with an open mind without ascribing any definite feature for plant or animal.

Plants which partake in ‘sexual’ reproduction, generally make seeds. The seed is a condensed or tiny plant within an enclosure. The enclosure guards the content from drying and helps to keep the ‘tiny plant’ alive for some time. For how long, depends on the plant variety.

SEED

The tiny plant is kept in a safe shell which allows for ‘breathing’. The ‘tiny plant’ stays dormant with very low activity, until activated by water. Each tiny plant has a root, a stem and just 1 or 2 leaves all in infancy, but ready to grow and establish. Root and Stem are at opposite ends; they regulate the growth of each other. Stem regulates root and vice versa. This is an arrangement of safety for growth.   If we fell the stem of a plant, the root triggers new stem growth; if roots get damaged, the stem triggers root growth. The two work as polar signals from opposite ends. Nature is a grand designer and ensures the safety of opposed structures by keeping their controls with the other end or terminal.

SIGNAL

For living systems, ‘signal-reading’ is a fundamental requirement. Seed grows only if it ‘understands’ that the environment is safe for growth. The most basic signal for life is ‘light’. Light is ‘read‘ for day break or day fall and accordingly functions open up or close down  respectively by day and night. Watch the ‘rain tree’ [தூங்கு மூஞ்சி மரம்]; by late evening, the leaves go to ‘sleep’ by closing upon one another and thus the Tamil name. Who tells the time? Light signal by its wavelength- predominance indicates the ending of the day. The signal reading facility is in the pigments which cause a number of chemical changes within. Nearly the same principle operates in causing‘flowering‘ of seasonal plants like Mango. Each mango variety responds to specific light / shadow [dark] ratio. Any alteration in the ratio can disrupt flowering. Also, flowering time generally coincides with every other support from the environment. You would have noticed a tiny beetle escaping from the ripe mango, as we try to cut the fruit. There is no external indication of any kind of the beetle [வண்டு] within.  When did it get in? Well before the flower could fall off. The beetle egg stays there for the length of time taken for the fruit to turn ripe. Each fruit variety and its beetle are mutually specific and take the same length of time to develop.  How nature has designed co-existence of plants / animal species is something to ponder over.

More to follow

Prof. K. Raman