Abstract
Intact dark- and light-grown mung bean (Vigna mungo L.), black bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) cowpea (Vigna unguicul a ta (L.) Wa lp.) and squash (Cucurbita pepo L.) seedlings on hydroponic medium were osmotically stressed by exposing their roots to PEG 8000 of various concentrations (-0.2 to -0.6 MPa) to determine stress effects on growth and tissue water status. Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress, and resumes within 10 to 45 min. Growth of all other seedlings were measured usually after 3 to 24 h stress, and in 3 h, elongation is inhibited in dark-grown and is stopped in light-grown tissues. In dark-grown mung bean, black bean and squash hypocotyls and pea epicotyls, growth rates after 24 h stress were found to be proportional to the Ψ of the medium. In mung bean hypocotyls, growth stopped before any change in Ψ or Ψ(π) occurred in the growing region. In this tissue and also in dark-grown squash hypocotyls, pea epicotyls, and in lightgrown cowpea hypocotyls, equivalent reductions in Ψ and Ψ(π) were evident in the growing region after 3 h, so turgor remained constant. In other species, osmotic adjustment with turgor maintenance was evident after 24 h in both the growing and expanded regions. The results with mung bean hypocotyls provided the first demonstration that stress causes an almost instantaneous stress-caused cessation of elongation in dicots. Since data from all plants showed that stress causes growth rate inhibition or cessation without a concomittant decrease in Ψ(p), it is concluded that turgor is not the factor regulating growth. More likely, stress-caused growth and water status changes are responses to an earlier signal, such as a stress-caused reduction in the apoplastic Ψ.
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Claims 9
Claim · model-written summary
Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress.
- Taxon
- mung bean
.jpg?width=60)
Vigna radiatae0 - Treatment
- any level of stresse0
- Outcome
- Growth of dark-grown mung bean hypocotyls ceasese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress, and resumes within 10 to 45 min”
Claim · model-written summary
Growth of dark-grown mung bean hypocotyls resumes within 10 to 45 min after osmotic stress.
- Taxon
- mung beanVigna radiatae0
- Treatment
- any level of stresse0
- Outcome
- resumese0
- Value
- 10 to 45 mine0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth of dark-grown mung bean hypocotyls ceases within 40 sec upon exposure to any level of stress, and resumes within 10 to 45 min”
Claim · model-written summary
In other seedlings, elongation is inhibited in dark-grown tissues at 3 h of osmotic stress.
- Taxon
- other seedlingse1
- Treatment
- stresse1
- Outcome
- elongatione1
- Direction
- inhibitede1
- Qualifier
- in dark-growne1
Not reportedComparator
Verbatim
e1“Growth of all other seedlings were measured usually after 3 to 24 h stress, and in 3 h, elongation is inhibited in dark-grown and is stopped in light-grown tissues”
Claim · model-written summary
In other seedlings, elongation is stopped in light-grown tissues at 3 h of osmotic stress.
- Taxon
- other seedlingse1
- Treatment
- stresse1
- Outcome
- elongatione1
- Direction
- stoppede1
- Qualifier
- in light-grown tissuese1
Not reportedComparator
Verbatim
e1“Growth of all other seedlings were measured usually after 3 to 24 h stress, and in 3 h, elongation is inhibited in dark-grown and is stopped in light-grown tissues”
Claim · model-written summary
In dark-grown mung bean, black bean, squash and pea hypocotyls and epicotyls, growth rates after 24 h stress increase with the water potential of the medium.
Verbatim
e2“In dark-grown mung bean, black bean and squash hypocotyls and pea epicotyls, growth rates after 24 h stress were found to be proportional to the Ψ of the medium”
Claim · model-written summary
In mung bean hypocotyls, growth stopped before any change in Ψ or Ψ(π) occurred in the growing region.
- Taxon
- mung beanVigna radiatae3
- Outcome
- growth stoppede3
- Qualifier
- before any change in Ψ or Ψ(π) occurred in the growing regione3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“In mung bean hypocotyls, growth stopped before any change in Ψ or Ψ(π) occurred in the growing region”
Claim · model-written summary
In mung bean, squash, pea and cowpea seedlings, equivalent reductions in Ψ and Ψ(π) were evident in the growing region after 3 h, and turgor remained constant.
Verbatim
e4“In this tissue and also in dark-grown squash hypocotyls, pea epicotyls, and in lightgrown cowpea hypocotyls, equivalent reductions in Ψ and Ψ(π) were evident in the growing region after 3 h, so turgor remained constant”
Claim · model-written summary
In other dicot species, osmotic adjustment with turgor maintenance was evident after 24 h in both the growing and expanded regions.
Verbatim
t0“mung bean (Vigna mungo L.) and other dicot species”
e5“In other species, osmotic adjustment with turgor maintenance was evident after 24 h in both the growing and expanded regions”
Claim · model-written summary
Turgor is not the factor regulating growth under stress, because growth is inhibited without a decrease in turgor.
Verbatim
e6“Since data from all plants showed that stress causes growth rate inhibition or cessation without a concomittant decrease in Ψ(p), it is concluded that turgor is not the factor regulating growth”