Agriculture Reference
In-Depth Information
filling can accelerate senescence, diminish seed set and seed weight, and
reduce yield (Siddique et al., 1999). This is because under such conditions
plants tend to divert resources to cope with the heat stress and thus limited
photosynthates would be available for reproductive development. Another
effect of heat stress in many plant species is induced sterility when heat is
imposed immediately before or during anthesis.
10.4.1 ANATOMICAL AND MORPHOLOGICAL REACTIONS
In tropical conditions, extra radiation and great temperatures are some-
times the major limiting factors that affect plant development and final
yield. Greater temperatures can lead to remarkable pre and postharvest
losses, burning of twigs and leaves, sunburns on stems and branches, se-
nility of leaf and abscission, prohibition in the development of shoot and
root, discoloration of fruit, and diminished production (Guilioni et al.,
1997; Ismail and Hall, 1999; Vollenweider and Gunthardt-Goerg, 2005).
In temperate regions, heat stress has been reported as one of the most
important causes of reduction in yield and dry matter production in many
crops (Giaveno and Ferrero, 2003). Reduction in number of fruits and
flowers, percentage of fruit fresh weight has also been reported (Golam
et al., 2012).
High temperature considerably affects the anatomical structures not
only at the tissue and cellular levels but also at the subcellular level. The
cumulative effects of all these changes under high temperature stress may
result in poor plant growth and productivity. A general tendency of re-
duced cell size, closure of stomata and curtailed water loss, increased sto-
matal and trichomatous densities and greater xylem vessels of both root
and shoot has been observed at the whole plant level (Anon et al., 2004).
At the subcellular level, major modifications have been found to occur in
chloroplasts, leading to significant reduction in photosynthesis by chang-
ing the structural organization of thylakoids (Karim et al., 1997). Studies
have revealed that specific effects of high temperatures on photosynthetic
membranes result in the loss of grana stacking or its swelling. Swelling of
stroma, disruption of vacuoles and mitochondria has also been reported
that result in reduced photosynthetic and respiratory activities (Zhang et
al., 2005).
