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Abstract
Effect of Rootstock on Growth and Water Use of Hevea
During Water Stress
The effects of three monoclonal Hevea
rootstocks on growth, water relations parameters, proline content in leaf
and water use efficiency of RRIM 901 scion clone during prolonged cycles
of water stress were studied. The plants, raised in plastic containers in
the glass house, were subjected to cycles of water stress for over a year
by irrigating either every alternate day (moderate stress) or once in four
days (severe stress). The three rootstocks imparted different stomatal responses
to the scion. RRIM 623 rootstock had drought avoidance characteristics as
the plants minimised water loss during severe water stress through effective
stomatal control in the scion shoot and by having deep rooting characteristics.
In contrast, GT 1 rootstock responded to drought by keeping stomata partially
opened as soil dehydration intensified allowing leaf photosynthesis to continue.
In common with RRIM 623 rootstock, plants on GT 1 rootstock had low pre-dawn
leaf water potential and high root: shoot ratio reflecting their deep rooting
characteristics. Plants on RRIM 600 rootstock was also very sensitive to
water stress but they seem to lack deep rooting characteristics. Plants
on GT 1 and RRIM 600 rootstocks tend to accumulate proline in leaves indicating
their ability for osmoregulation. Data obtained in this study indicated
that plants on GT 1 and RRIM 623 rootstocks are better adapted to prolonged
drought than those on RRIM 600 rootstock by virtue of their deep rooting
characteristics.

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