MSc

A pot culture experiment was conducted at the College of Agriculture,
Vellayani during the year 1997 - 1998 to study the effect of shade on biomass
production and partitioning of photosynthates in ginger cv. Rio-de-Janeiro. The
experiment was laid out in completely randomised design with five shade levels (open,
20, 40, 60 and 80 per cent) and four replications. Artificial shade was provided using
high density polyethylene shade nets and calibrated using quantum photo sensors. Two
months after planting, ginger plants were labelled using 14C . After tagging, one set of
samples were collected immediately. Subsequently, harvesting of the tagged plants
were done once in sixty days after labelling. Monthly observations of various growth
parameters were taken from two months after planting. At six months after planting
photosynthetic related parameters were measured using leaf chamber analyser.
The various growth parameters like number of tillers, leaf area, leaf dry weight,
dry matter production, crop growth rate, relative growth rate, net assimilation rate at
final stage, leaf area index which contributed to yield was highest under 20 per cent
shade. This shows that the plant prefers low shade intensity compared to open. The yield
recorded under 20 per cent shade was significantly superior compared to open. But the
yield at open and 40 per cent shade were on par. Higher shade levels decreased the yield.
This shows that the crop can tolerate shade up to 40 per cent.
Different shade levels influenced the quality of ginger rhizomes. While volatile
oil was maximum under heavier shade levels in general ( 60 and 80 per cent ), non-
volatile ether extract was higher under 20 per cent shade. Starch as well as crude fibre
content was more in plants grown under open condition.

The photosynthetic rate and related parameters of ginger were measured at six
months after planting using leaf chamber analyser. Photosynthetically active radiation
on leaf surface as well as stomatal conductance was high under open condition. But
leaf internal carbon dioxide concentration as well as stomatal resistance was high under
heavier shade levels (60 and 80 per cent). Photosynthetic rate as well as the
transpiration rate was maximum in plants grown in open. Though, at 20 per cent
shade, the photosynthetic rate was less, the yield was high. This might be because of
the photo oxidation that has taken place at high light intensities or due to the inefficient
translocation of the photosynthates in open condition compared to 20 per cent shade.
Radio tracer analysis done using labelled 14C has shown that under open
condition, though initial intake of carbon dioxide was more, most of the carbon dioxide
taken are seen in the above portion itself. While in 20 per cent shade most of the
carbon dioxide taken in has translocated to the lower portion. This shows that under
low light intensity the photosynthates produced has translocated efficiently to the
lower portion while in open condition efficient translocation has not taken place.
The results indicate that 20 per cent shade level is favourable for growing
ginger plants to get higher rhizome yield. The yield at 40 per cent was on par with that
of open. This shows that crop can tolerate shade upto 40 per cent. Thus the partially
shaded coconut gardens can be exploited for increasing the area under ginger which
may help in doubling the production.