Some more interesting facts on Physiology and Biochemistry

Hitchcock and Zimmerman exhibited that flowering in Nicotiana can be enhanced by auxins.

Auxins are synthesised mainly in apices and exhibit polar transport.

Crescograph:

Used for recording plant growth in seconds.

Plants having deliquescent stem have poor apical dominance while plants having excurrent habit (palms, conifers, polyalthia) have greater apical dominance.

IPA (Isopentenyl adenine):

Most widely occurring cytokinin, isolated from Pseudomonas tumefaciens.

IAA:

Promotes the liberation of a water soluble xyloglucan from the cell wall.

Mowing of grass:

Removes apical bud, dwarfism, inhibit seed germination and seedling growth, overcome apical dominance, break bud dormancy, reduce leaf growth and curvature movements, stimulate growth of primary root but inhibit growth of lateral roots. They affect flowering, fruiting and sex expression.

Ephemeral movements:

Once in life e.g., expansion of leaf.

Clinostat/Rlinostat:

Instrument which can eliminate the effect of gravity and allow a plant to grow horizontally by slowly rotating it.

Perceptive region:

The area of perception of stimulus.

Responsive region:

The area of response.

Presentation time:

The minimum lime required for a stimulus to become effective.

Reaction time:

The period required for a stimulus to exhibit response.

Relaxation time:

Time required for the effect of a response to disappear.

Weber-Fechner law:

(i) Within limits, the equal relative differences between two stimuli of the same type are equally perceptible.

(ii) There is a tendency of the intensity of sensation to vary as logarithm of the stimulus.

Richmond-Lang effect:

Cytokinin prevents chlorophyll degradation, hence ageing.

Sleep disease (in rolling of petals in opened (lowers) is caused by ethylene. Even 1 ppm of ethylene prevents the opening of flower buds.

Tromatropism:

Movement induced by injury.

Photomorphogenesis:

The control of development of form (i.e., morphogenesis) by light.

Phytochrome:

Proteinaceous pigment. The sensitivity of seeds to the effect of red and far-red wavelengths of light is due to the presence of phytochrome. It is a regulatory pigment which regulates several light-dependent developmental processes in plants.

ABA:

Inducing synthesis of carotenoids and turns green organges into yellow.

Automatic or Pfeffer’s auxanometer:

Register total growth, rate of growth at specific time and overall pattern of growth. An improved auxanometer over the arc auxanometer.

Phenology:

The different aspects or appearances of plants in different seasons of a year.

IAA destruction:

Takes place due to photo- oxidation by blue light and dark oxidation by IAA oxidase.

IAA-aspartic acid, IBA-alanine:

More effective in bound state.

Human Urine:

Also natural source of auxins.

DCMU (Dichlorophenyl dimethyl urea):

Strong inhibitor of photosystem II.

Impaction:

Treatment given to seeds when they are shaken vigorously.

Antiauxins:

Compounds which compete with the auxins for the reactive site e.g., TIBA, 4-chlorophenoxy isobutyric acid, 2, 6-dichlorophenoxy acetic acid, 2, 4-dichIoroanisole.

Gibberella fujikuroi:

A fungus causes “Foolish seedling disease in rice plant in Japan. Gibberellin (a growth hormone) was first extracted from this fungus.