Protected Cultivation 191
prevalent in the region can be overcome allowing almost round the year cultivation,
increased productivity by 25%–100% and in certain cases even more, as well as
conservation of irrigation water by 25%–50%. Plain architecture can be maintained
through application of plant growth regulators. Most plant architecture traits can
be directly retraced to changes in activity and/or size of the shoot apical meristem
and derived meristems, namely lateral or axillary and floral meristems. The activ-
ity of these meristems is determined both by the plant’s genetic programmes and
environmental factors. Plant’s growth and development depend on carbon nutrient
status. Processes that especially require significant energy input are phase transitions
and the initiation, and outgrowth of new shoot organs, such as floral transition and
lateral branches or flowers, respectively. These processes are of vital importance to
plant productivity and have major impact on reproductive output and thereby yield
in many fruit crops. Timing of flowering depends on the environmental conditions
and internal signals from the plant’s genetic program to induce flowering in plants
at the most favourable conditions. Most studies focused on highly predictable’ fac-
tors involved in flowering like day length photoperiod and extended periods of cold.
However, less predictable factors, including ambient temperature (15–30°C) are
equally important. One or more of the factors such as temperature, light, CO 2 con-
centration, RH, access to insects and pests, etc., can be controlled to desirable limits
to manipulate flowering and fruiting for early and multiple harvest under controlled
environment. Commercial production of fruit plants particularly grown under open
field conditions will be severely affected by biotic and abiotic factors increasing
the gap between expected yield and obtained yield. Under polyhouse cultivation in
tropical and subtropical areas, severe fungus infection along with sun burning of
leaves in summer, faster growth of trees and poor quality of fruits is obtained. Due
to high temperature, physiological disorders like, sun burning, sun scaled, flower
and fruit abscission, seed discolouration, etc. will be more pronounced (Figure 17.1).
The challenge to reduce the gap between the expected yields and observed yields can
be minimised by protecting the valuable fruit crops through greater use of green-
house technology and adoption of high-tech horticulture for judicious management
of natural resources (Prakash and Singh 2006).
FIGURE 17.1 Leaf burning during summer under polyhouse cultivation due to high tem-
perature.