Abstract:
The present study on Photosynthesis and enzyme activity regulating starch
biosynthesis in different varieties of cassava (Manihot esculenta Crantz) was
conducted during the period of 2015-2016 in the Division of Crop Production,
ICAR-CTCRI, Thiruvananthapuram.
The objective of the study was to study the relation between
photosynthesis, leaf area, crop duration and enzymes activities regulating starch
biosynthesis in four varieties of cassava (Manihotesculenta Crantz) and to
determine limiting factor(s) for low starch content of tubers in low starch
varieties. Four varieties selected for the study are viz., SreeVijaya, SreeAthulya,
H165, H226. SreeAthulya, a triploid long duration variety had the maximum
starch and sucrose content whereas H165, a short duration variety, had the
minimum starch content.
The different parameters such as morphological, biochemical, enzyme
activity, and photosynthetic activity were recorded / assayed for four cassava
varieties. Morphological parameters are number of leaves, leaf area, leaf area
index and tuber yield. Maximum noumber of leaves and leaf area was observed in
the variety SreeVijaya. Photosynthetic activity was observed maximum in the
variety SreeVijaya. The minimum number of leaves and leaf area were observed
in the varieties H226 and H165. The maximum tuber yield was observed in the
variety H226 and minimum tuber yield was observed in the variety H165.
Biochemical parameters like sucrose content and starch content were maximum in
in the variety SreeAthulya and minimum in the variety H165.
The enzymes activities involved in starch biosynthesis assayed in the
present study are viz., AGPase, SPS, SS, SuSy and invertase. SreeAthulya had the
highest AGPase activity and SuSy activity and high tuber yield. SreeVijaya had
the highest SPS activity. H165 had the lowest tuber yield due to decrease in leaf
area, sucrose and starch content, photosynthetic activity, lowest enzymatic
activities of SuSy, SS. Generally the photosynthetic activity the activities of
AGPase, SS and SuSy enzymes were high in high starch variety SreeAthulya. The
present study reveals low activity of enzyme sto be the rate limiting for low starch
content of varieties H165. Low starch content varieties can be improved by
manipulating the activity of these enzymes.
