Fill in the places with appropriate word/words.
(a) A phase of growth which is maximum and fastest is ............. .
(b) Apical dominance as expressed in dicotyledonous plants is due to the presence of more ............ in the apical bud than in the lateral ones.
(c) In addition to auxin, a ............ must be supplied to culture medium to obtain a good callus in plant tissue culture.
(d) ............ of a vegetative plants are the sites of photoperiodic perception.
(a) A phase of growth which is maximum and fastest is exponential phase.
(b) Apical dominance as expressed in dicotyledonous plants is due to the presence of more auxins in the apical bud than in the lateral ones.
(c) In addition to auxin, a cytokinin must be supplied to culture medium to obtain a good callus in plant tissue culture.
(d) Leaves of vegetative plants are the sites of photoperiodic perception.
Plant Growth Substances (PGS) have innumerable practical applications. Name the PGS you should use to
(a) increase yield of sugarcane
(b) promote lateral shoot growth
(c) cause sprouting of potato tuber
(d) inhibit seed germination
(a) Gibberellic acid increases the yield of sugarcane.
(b) Cytokinin spray on plants promote lateral shoot growth.
(c) The effect of ethylene on potato causes its sprouting.
(d) ABA - Abscissic acid inhibit the seed germination.
Growth is dependent on three factors - initial size $\left(W_0\right)$, rate of growth $(r)$ and time interval (+) for which the rate of growth is retained.
Where,
$$ \begin{aligned} W_1 & =W_0 e^{r t} \\ W_1 & =\text { final size }, \\ W_0 & =\text { Initial size }, \\ r & =\text { growth rate, } \\ t & =\text { time, } \\ e & =\text { base of natural logarithim. } \\ 19 & =5 \times(2.7)^{r \times 7} \\ \frac{19}{5} & =(2.7)^{r \times 7} \\ 3.8 & =(2.7)^{r \times 7} \end{aligned}$$
$$ \begin{aligned} &\begin{aligned} \log 3.8 & =r \times 7 \times \log (2.7) \\ 0.5798 & =r \times 7 \times 0.4314 \\ \frac{0.5798}{7 \times 0.4314} & =r=0.1907 \\ \text { Relative growth rate } & =\frac{\text { Growth in given time period }}{\text { Measurement at start of time period }} \\ & =\frac{19}{5}=3.8 \mathrm{~cm} \end{aligned}\\ &\text { Thus absotule growth rate is } 0.1907 \text { while relative growth rate is } 3.8 \mathrm{~cm} \end{aligned}$$
Gibberellins were first discovered in Japan when rice plants were suffering from bakane (the foolish seedling disease) caused by a fungus Gibberella fujikuroi.
(a) Give two functions of this phytohormone.
(b) Which property of gibberellin caused foolish seedling disease in rice?
(a) The hormone, gibberellin
(i) Produce the phenomenon of bolting, i.e., the growth of the internodal region of stem in rosette plants.
(ii) Induces seed germination and break bud and seed dormancy.
(b) The rice seedling/plant show excessive growth in their internodal region when get infected with fungus Gibberella fujikuroi. This fungus produces excessive amount of plant hormone GA which makes plants taller than the normal plant foolishly and many result into death of the plant.
Besides some primary function, both gibberellins and ethylene have some special effect on some specific plants as Gibberellin promotes the formation of male flower an genetically female plants while ethylene promotes formation as Female flowers an genetically, male plants.