Tag: living world of plants - plant physiology

A) Joseph Priestley first discovered oxygen and discovered that it is released by plants.
B) Jan Ingenhousz proved that sunlight is essential for photosynthesis.

• Symplast was first given by Eduard Tang in 1879 who discovered plasmodesmata.
• In 1880, Hanstein coined the term symplast.
• But these both terms are given together by Munch in the year 1930.

Boussingault was a  French chemist and he made a very significant contribution to the fields of agricultural science and metallurgy.

Melvin Calvin was the professor of chemistry. He was awarded the nobel prize for chemistry for the discovery of various pathways of photosynthesis. 3-phosphoglyceric acid as first $CO _{2}$ fixation product in algal photosynthesis was discovered by Calvin. He used radioactive $^{14}C$ in algal photosynthetic studies. This led to the discovery that the first $CO _{2}$ fixation product was a three-carbon organic acid. He also helped to mark out the complete biosynthetic pathway, hence it is named as Calvin Cycle. The first stable product identified was 3-phosphoglyceric acid (PGA), hence it is named as $C _{3}$ pathway. Calvin cycle occurs in all photosynthetic plants whether they have $C _{3}$ or $C _{4}$ pathway.

Photosynthesis takes place in the green leaves of plants and other green parts of plants like stem etc. The most active photosynthetic tissue in higher plants is the mesophyll of leaves. Mesophyll cells have many chloroplasts, which contain the specialized light absorbing pigments. These pigments are known as photosynthetic pigments. Chlorophyll and carotenoids are the types of photosynthetic pigments. Chlorophyll is the primary pigment and carotenoids are the accessory pigments. Chemistry of photosynthetic pigments was first studied by Willstatter and Stoll in 1912. They discovered that chlorophyll has a tadpole-like configuration. It has a head called porphyrin and a tail made up of long chain alcohol called phytol. Porphyrin head is made up of four pyrrole rings which are linked by methine bridges. 5 atoms— 4 carbon and one nitrogen form the skeleton of each pyrrole ring. Nitrogen lies towards the centre. Thus, the correct answer is option A.

Photosynthesis is a process by which green plants manufacture their food with the help of carbon dioxide and water in the presence of sunlight. It was discovered by Jan Ingenhousz. Through his experiments, he showed that sunlight is essential for the plant process that helps to somehow purify the air fouled by the breathing mouse and the burning candle in Priestley's bell jar experiment. In another experiment with an aquatic plant (Hydrilla), he showed that in bright sunlight, small bubbles were formed around the green parts of the plant while in dark, no bubbles were formed. He identified those bubbles to be of oxygen. Thus, the correct answer is option B.

T.W Engelmann: He described the first action spectrum of photosynthesis. By using a prism he split sunlight into its spectral components (VIBGYOR) and then illuminated green algae Cladophora placed in a suspension of aerobic bacteria. The bacteria were used to detect the sites of O$ _2$ evolution.

Ethylene is a simple Gaseous PGR(Plant growth regulator). The hormone finds its use in increasing the yield of cucumber plant by increasing the female flower formation. 

A) Stephen Hales is called the father of plant physiology for his extensive research on photosynthesis.
B) Joseph Priestley showed that animals exhale carbon dioxide (impure air) and plants give out oxygen (pure air).
C) Ingenhousz showed that light is essential for photosynthesis.
D) Von Helmont proved that plants require minerals from the soil for photosynthesis.
So the correct answer is 'Priestley'.

• F.F. Blackman, a British plant physiologist discovered that photosynthesis is a two-step process and only one of which uses light directly.
• Hill discovered that green particles obtained from broken cells could produce oxygen from water in the presence of light and a chemical compound, such as ferric oxalate, able to serve as an electron acceptor. This process is known as Hill reaction.
• Benson was the co-researcher of Calvin who discovered the Calvin cycle in photosynthesis.
• The process of photosynthetic photophosphorylation was discovered by Arnon. Photosynthetic photophosphorylation is the process of phosphate group transfer into ADP to synthesize energy-rich ATP molecules making use of light as an external energy source. So, this option is correct.