Tag: living world of plants - plant physiology

Joseph Priestley discovered that plants produce oxygen.
Jean Senebier discovered that the source of this carbon is carbon dioxide. 
Sachs discovered that starch grains are produced in plant leaves and  these are the first visible product of the process of photosynthesis. 
Jan Ingenhousz discovered that light plays a major role in photosynthesis. 

• Most of the experimental work in photosynthesis has been done on Chlorella. Through photosynthesis it multiplies rapidly, requiring only carbon dioxide, water, sunlight and a small number of minerals to reproduce. 
• It is easy to culture and it is easy to understand the photosynthetic process in chlorella cells.
•  Based on the above advantages most of the photosynthetic work was conducted in chlorella compared to hydrilla, spinach leaves, and Chlamydomonas. 

The correcr answer is ' Sachs ' . Sachs stated that green parts in the plants produces glucose which is later stored as starch and this starch is the first visible product of photosynthesis . in 1865 Sachs proved that chlorophyll was confined to special bodies only , which was later termed as Chloroplasts .

Van Helmont concluded that plants get their food from water. Van Helmont wanted to prove plants use materials from the soil to perform photosynthesis and done an experiment and proved that.

Thigmonasty or seismonasty is the nastic response of a plant or fungus to touch or vibration. Examples are many species in the leguminous subfamily, Mimosoideae, active carnivorous such as Dionaea and a wide range of pollination mechanisms.

External stimulus induces tropic, nastic and tactic movements.

1. Tropic movement - biological phenomenon indicating growth or turning movement of a plant, in response to an external stimuli.
2. Nastic movements - Non-directional responses in response to external stimulus
3. Tactic movements - It includes phototactic, chemotactic and thermotactic movements.
   

According to the second law of thermodynamics, spontaneous processes in a system at constant temperature and pressure occur with a decrease in Gibbs free energy.

Nastic movements are non-directional movements in which direction of response or movement is determined by the structure of responsive region. Nastic movement for instance, could be due to changes in the turgor pressure.

Seismonasty is defined as the nastic movement in response to shock, especially rapid folding of te leaflets of the sensitive plant due to changes in turgor pressure caused by vibration. It is also called as thigmonasty, because the external stimuli is touch.

Photonasty - the tendency in certain plant species to respond to light by developing sufficient cellular force or growth on one side of an axis to change the form or position of the axis, as in the opening and closing of the flowers of four-o'-clocks.